Procedures

SUBJECT: TCS operations tcsiii\genprocd.lst

TITLE: General procedures

DATE: 25 March 1993

AUTHOR: W. Cruise REVISION: 0.2

Introduction

Purpose :

This paper provides detailed, step-by-step instructions for performing many of the procedures required to checkout and operate the telescope. It was written for Electronics Group personnel to use in the performance of system checkouts and troubleshooting. It may also be very useful to Telescope Operators, and others, who occasionally need a step-by-step guide to telescope operational procedures.

NOTICE: Due to the demise of the Electrnics Systems Group I have not be regularly updating the stuff in here. Some is good, some is hopelessly out of date. Use at your own risk. However, some of this is really the only docs on some of these ops.

A lot of the TCS III stuff has been updated on 29 Aug 1997.

Usage :

For the most part, it is not arranged in operationally sequential order, but is intended to be used as a reference manual.

Guide TV camera

The idea here is to test the guide camera signal and control paths, the leaky, and some monitors. Hopefully the simple test and troubleshooting procedures can catch some of the common problems.

Camera setup

make sure that the camera is physically installed and connected.
check that the proper patch connection is made at the BNC patch panel in bay 1 in the computer room. The correct focus' camera should be patched to Leaky 1. This should be indicated on the run checklist.

Equipment setup

turn on the observer's monitor, go to channel 2
turn on the Colorado Video crosshair generator
turn on Leaky 1. This is the bottom of the two leaky memories in bay 2 of the control console
- Leaky 1 should be set to digital.
- Integration time should be 0.25, or 0.5 seconds.
- black and white levels should be set near the reference marks on the panel. Do not change unless they are way off these marks.

Power on camera

verify gain turned to minimum
select the proper camera with the camera select knob. The camera control is mounted below the leaky memory, in bay 6 of the T.O. console.
turn on the camera power controls for the selected camera.
- The pushbutton should light when pressed.
- If the pushbutton does not light, it may indicate
  - a bad connection to the camera
  - no AC power to the camera
- Wait about 30 seconds for the camera to warm up and produce a signal
  - when first turned on you should see evidence of video, and the Leaky should have an XYZ readout on the channel 2 monitor. If this does not happen, check the Colorado Video, and the monitor selection.
  - if it still doesn't happen, check for power at the TV camera, and various cable problems which might have happened.

Check that the camera sees light

Once the camera has shown evidence of a signal (not just video), advance the gain a bit, until it is seeing light. Do not overdo it here!
In a very dark dome, the pattern may not be outstanding, but at least you should see the noise go up at high gain.
If you get no signs of signal, but do have video, you should probably try another camera. Call first.

TCS clocks

DATE command

This checks the internal, software date being used by HP 1000 computer running the telescope.

it is possible, through crazy circumstances, for this computer to get WAY OFF in the date.
type the DATE command. It will display the current UT date. Check for correct date, and especially the correct year.
if it is incorrect, call Bill Cruise, as a software fix is in order. It is not easy to do!

Reset TCS solar clock

Due to various drifts in the clocks, it is useful to insure that the internal, hardware TCS clock is exactly on. The clock is located in bay 3 in the computer room, above the tape drive, and below the WWVB clock.

To set the clock insure the WWVB clock is working and synchronized to the correct time. No warning lights should be illuminated on the front of the receiver. If they are, do not proceed with setting the clock.
On the thumbwheels, dial in a time, to the second, some short time ahead of the current time in the WWVB clock display.
Sometime during the second BEFORE the WWVB clock shows the dialed in time, press and release the SOLAR SET button.
At the end of that second, the TCS clock will be set exactly to the time in the dials, to a resolution of about 10 msec. There is no need for any other synchronization.
After setting the clock, you should verify that the UNIVERSAL TIME LED's on the TCS console show the correct time.

Reset sidereal time

This is the sidereal time displayed in the SIDEREAL TIME LED's on the TCS console. It is not used for anything except the operators convenience, but should be correct.

It is reset in a computer assisted operation.
Command SSID on the TCS console.
This will print a value on the screen which will be the correct sidereal time in about two minutes.
Using moderate haste, go into the computer room and set this value into the clock thumbwheels.
Then press the SIDEREAL SET/CPU SET pushbutton, located below the thumbwheels, two times.
This should illuminate the CPU SET part of the button.
Sometime later the TCS will reset the clock, and the light will go out.
Verify the time on the LED's. If it is off by a minute, perhaps you were too slow!

Reset the System D computer

NOTE: the System D computer no longer works!

The SYSTEM D computer, located in bay 5 in the computer room, provides drive for some of the LED displays on the TCS console. In a strict sense, it is not needed, but it is very useful.

Possible reset scenarios for this computer

If it is running, you can skip the boot procedure, and go to the setting. If it is dead, you may have to boot it first. However, first try the setting procedure. If there is no life, go to the boot.

Boot procedure

Turn on the paper tape reader, in bay 4, using the POWER button.
Press the LOAD button, and place the leader of the tape under the lights.
Press READ.
On the SYSTEM D CPU, use the horizontal pushbutton under the 16-bit register to select the "S" register in the horizontal
Use the individual switches under the 16-bit register to set it so that lights are illuminated under the paper dots, and off elsewhere. Pressing CLEAR first will turn off all the lights.
Press in sequence;
- STORE (lower right),
- PRESET (lower left, top of switch),
- IBL (lower left, bottom of switch),
- PRESET, and
- RUN (far lower left, top of switch).
Tape will stream through the reader, so just stand back and let it happen.
When the tape is done, press FEED to get it out of the reader. Be sure to turn the reader POWER switch OFF.
Find the tape rewinder in the far left corner of the computer room, near the fire extinguisher control. CAREFULLY wind up the tape (it's our only copy).
continue with the normal resetting procedure in the next step.

Normal, non-boot reset procedure

At the System D computer, turn the KEY SWITCH one position CCW, and then back to RUN.
The computer should start, with one light on in the next-to-leftmost bit of the 16-bit register.
Next, the computer is going to run a simple dialog in the lights, and you must respond by entering values with the S-register switches.
- Note that the first light is under the Dymo label, YR. This indicates that you must enter the current year. The year number to be entered is in excess of 1980, so a value of 13 is required for 1993. Notice that the rightmost 8 bits of the register are labeled for BCD digit entry. To enter a 12, the lights would be in the pattern of 0001|0010, where a zero indicates an off light, and a 1 an on light. You can also use the BCD bit values (8, 4, 2, 1 positionwise) to verify, by adding up the weights of all the on buttons.
- To enter this number into the system and move to the next item, press the GO button, which is the far left bit of the 16-bit register.
- When GO is pressed, the light under YR goes out, and the one under MO comes on.
- Set the current month in the BCD digits, and press GO. Months are simply 1 for Jan, through 12 for Dec.
- DY is lit next. Put in the UT date and press GO. Make sure you use UT, and not local. Look at the WWVB radio. If it is past 0, and you are in the afternoon after 2 PM local, it is already tomorrow UT.
- HR is the next item. Get the current UT hour from the WWVB clock. Press GO.
- MN is the last item. Minutes should also come from the clock, and should be the very next minute which will occur. Make sure you have enough time to get it set in before the clock hits the minute. The computer will simply take the number you put in, and a hardware minute signal from the solar clock, and connect the two internally.
- When you press GO, the 16-bit register starts a rapid, binary count until the minute signal. At that time it will begin a slow count, indicating it is cycling, reading the encoders and updating the displays.
- At the TCS console, notice that all the following LED displays seem correct: HA, DEC, Dome position, and Dome misalignment.
- Press DATE TIME SET pushbutton in the middle row on the right of the TCS console. The HA LED's should change to show the year, month, and day. The DEC LED's should show sidereal time. Compare them to the TCS channel 14 sidereal time. It should be within a second. Return the pushbutton to RA HA/DEC.
- If you have a failure at this, skip the booting, cycle the power switch, and try to reset System D again. The problem is most likely in the setting procedure.
- Keep the faith and hope this system disappears soon.

Telescope focus:

TCS focus readout

This is intended to test the upper end focus motion and the focus encoder The upper end must have been cabled for this test to work.

The upper end must have been cabled for this test to work.
The TCS channel 14 TV display must be showing the correct focus.
- The focus name is just above the focus encoder readout.
- If it is wrong, or it says "HUH??", you must either log off and back on the TCS, or use the FOCUS command to switch to the correct focus.
- The preferred method is to log off and back on. It will then automatically determine which focus is being used.
- If it does not do this correctly, there is either a cabling problem, or an encoder problem.
Prime focus
- Use the focus buttons on the end of the observer's handset, to move the focus motion
f/8 & f/35
- Use the separate ASA focus pushbutton box
First move the focus near the position specified on the checklist
move the focus about 1000 units on both sides of the specified position
this will ensure that the nominal focus area on the focus mechanism has been run a bit to loosen things up.
use both slow and fast motions in both directions
Leave the focus at the specified position.
When the observer will not be in the main control room, perform focus motion testing with the handset that the observer will be using.
- At coudé, only the RA/DEC handset has focus control. The focus buttons on the XY handset do not work.
- If the f/8 or f/35 upper end is used in the back room, ensure the focus box is moved to the back room, and works there. There may need to be a connector change.

Troubleshooting focus problems :

If the encoder reading does not change, or does not move both directions at both speeds, you must troubleshoot the problem. This is a major malfunction, and will seriously affect observing. If it is not fixed after a bit of initial troubleshooting, inform the TIC so the priority can be advanced, and additional help obtained, if needed.

First, try to isolate the problem to either the focus encoder, or the focus system:
encoder problems:
- the readout is all zero's, or it is a suspicious number like 2047, 4095, or 8191.
  - there is a very good chance that the encoder is not connected, or it is not powered up. The encoder reading card may be seeing all the lines as opens, which it is pulling up to 1's.
  - there is a possibility that the TCS computer is reading the wrong encoder. Verify that the computer has the right focus name on the display. It will try to read the encoder for the named focus.
- the encoder shows a number which is not changing, and is not closely linked to a power of 2
  - it is likely that the encoder is not being driven. Look to focus motion problems.
focus system problems: select which system is in use, and then try these in order:
- f/8 and f/35
  - these focus systems use computerized controllers in the computer room.
  - ensure the Transduction computer (bay 2, computer room) is running, and has been booted with the correct disk. Current procedures should be in the TIC checklist.
  - check the servo box below the Transduction. It should be powered on, the fuses should be good, and the big red button should be out.
  - ensure the button box is really connected.
- Prime focus and coude:
  - check focus system power:
    - 120 VAC single phase must be on to control station 6 at panel F, in the control room. This will also affect the encoder.
    - for prime focus only, the telescope 48 volts must be on at panel F, and the power supply (monster HP in crawl space, near south pier) must be indicating 48 volts.
    - 48, and 120 volt breakers must be on inside control station 6. The breaker panel is behind door 3, on the north side of the telescope.
  - check DC MCM 9, behind door 2, in the top row. Its breaker should be on, and the green 48 volt light should come on when focus is tried at high speed.
  - check ILM (interlock module) 11, in the bottom row. It also has breakers for both fast and slow motions, and some indicator lights which may help in troubleshooting.
  - a low voltage Lambda power supply provides power for slow speed. It is located behind door 3, and is strapped to the chassis above the circuit breakers.
if the controls seem to be working, physically inspect the focus motion
- have someone operate the system while another looks for motion at the drive.
- if the motion does not work, and it appears the controls are working, perform more electrical, and perhaps mechanical troubleshooting.
- if the motion works, direct the troubleshooting toward the encoder system.

M2 Operations

the M2 command

This command on the TCS simply runs a program which was originally written for engineering work. This should clue you in to the quality to expect.

if the display from the program does not use the top two lines, and overflows the usable terminal screen, it is possible that the MEMORY LOCK on the terminal is active (even if there is no light on). Try exiting the program, pressing the MEMORY LOCK button, and trying again.
at the top of the program screen should be a statement like "M2 is in coudé mode using the red mirror". It is also possible for it to say that the M2 is in an unknown mode
below this is a list of all the M2 devices, and their current status
at the bottom is a menu of all operations which are possible.

check for proper status

for bare FOCAM or HRCam runs, all mirrors must be down, and the rest lock must be locked. If this is the condition, the top line should say "M2 is in prime focus mode".
for coudé mode, it should indicate the system is in coudé mode, with the proper mirror in place. Check with the Optics Group for the required mirror.

reposition the mirrors , if needed:

on coudé runs, do not move anything without consulting the Optics Group. They are very particular about their alignments, and typically don't want anything disturbed.
also, do not move anything without notifying anyone who may be in the prime focus cage.
use the M2 program menu commands to move the mirrors
- rest lock must be unlocked before moving any mirrors
- if any mirror is up, it must be unlocked first and then moved down
- only one mirror can be moved up at any one time.
- if any movement has an active interlock status on the display, it is prohibited to move it. The hardware interlocks will prevent any movement of that device.
- after moving a mirror up, use its lock to hold it in place
- it takes about 10 seconds for the locks to operate, but up to a minute and a half for the mirrors to move.
- if a mirror motion times out, try again
- the rest lock must be relocked after moving the mirrors
only when everything is right will the top status line indicate the configuration:
for coudé mode, one mirror must be up and locked, and the remaining mirrors down and the rest lock locked
for prime mode, all the mirrors must be down and the rest lock locked.

troubles moving the mirrors :

if a mirror is not at either the up or down position, it may be impossible to move it. In any case, only try to move it down, as it is probably safer.
the interlocking is designed to prevent damage to the mirrors, but it sometimes causes troubles when mirrors have moved slightly off their limits.
the computer control exactly parallels the control which is possible from the control station, using the MCM's directly. Therefore, if the system is locked up at the computer, it will be similarly locked up from the MCM's
however, it is easily possible to circumvent the interlock system, and move mirrors when things won't work from computer.
- such movement is quite dangerous, and it is easily possible to run the mirrors into each other.
- only attempt non-interlocked operation if you fully understand how the M2 system operates, and you have made a visual inspection of the current state of the M2 unit
- call for help before attempting the non-interlocked operation if you have any doubts about the procedure.
- to circumvent the interlocks, pull the M2 interlock module, ILM 5. It is located behind door 2, in the bottom row.
- unscrew it, and pull it out slightly to disconnect it.
- using the MCM's behind door 1, move the mirrors to their down positions. If more than one mirror was up, move the mirrors closest to the bottom first. Take each MCM off-line to permit local operation, and put it back on-line when done.
- if you want to do all the motions from the MCM's, it is highly recommended that the ILM be reinstalled as soon as the interlocked condition is cleared. It will guarantee a safe sequence. In any case, do the motions in the same order that would be used at the computer.
- when done, push the module in, and lock the screw.
- complete the moves at the computer, if at all possible

Autoguider system:

A/G handpaddle extension to Upper Coudé J10 (or J11)

this is for coudé only

in the 4th floor back observing room, at the left side of the console, near the HP terminal for moe, there is a connector on the front of the "V" panel for a Leak Memory handset. Hanging from the cable tray is a cable which can connect from this handset connector to the coudé room, by using the instrumentation cabling.

connect the cable to the console connector

find the other end of the cable, which should be connected to the coudé instrumentation cabling panel, and determine which connector it is on — J10 or J11

if the autoguider handset box is on the 4th floor, take it down to coudé.

in the coudé room, on the 3rd floor, install the handset box to the same numbered connecter used on the 4th floor.

test this box in the same manner as the T.O.'s handset box.

AGBOX sees image in box

this is not applicable for AOB, HRCam, SIS, or for other instruments with their own, internal guiders. However, as some of those instruments will set up using the TV guider, perform it anytime it appears on the TIC checklist
AGBOX reads the leaky memory area around the guiding box (16x16 pixels) and displays it on the TO console in a pseudo 3-D plot.
it is a very good test for autoguider problems, as it tells whether the computer is communicating with the Leaky. If this works, then guider problems are probably due to configuration errors.
get some signal on the leaky display that will show up in the plot
- at cass, the flaw on the TV camera serves well. Put a dot in the center of the box.
- at other foci, turn up the gain and get some noise or a light gradient.
- if on the sky, find any reasonable star
command AGBOX at the T.O. console
the plot should have some resemblance to the signal, with the blacker areas near the bottom, and white areas much higher.
if the plot is max'ed out, perhaps the Leaky is off, or something is disconnected either behind the Leaky, or at the CAMAC crate in the computer room.

Setting up the HP 1000 terminal

Sometimes, for whatever reason, the buttons on the HP 2648 terminal get messed up, and make terminal operations difficult, or impossible. Use the following procedure to undo and reset the terminal.

Hard reset

Quickly pressing the RESET TERMINAL button two times will do a complete reset on the terminal internal status, wiping everything out, and putting it back to a power on status.
Often this is the best way to undo inadvertent changes in setup. There are more subtle ways, but they will not be discussed here.
Hard resetting of the terminal, however, does not change the switch settings.

Switch settings

The DUPLEX switch, upper left, should be set to FULL.
The PARITY switch, upper left, should be set to NONE.
The BAUD RATE knob, upper left, should be set to 9600.
The buttons on the upper left of the terminal should be set up as follows:
- DISPLAY FUNCTIONS - OFF
- BLOCK MODE - UP
- REMOTE - DOWN
- CAPS LOCK - don't care
- MEMORY LOCK - OFF, preferably. If on, it causes an area at the top of the screen to be "locked", and not scroll. If this area, perchance, takes up most of the screen, it is more a problem than a feature.
- AUTO LF - UP. This can cause some crazy problems with getting prompts on the terminal if it is down.

Terminal troubleshooting

This section gives some quick checks and fixes for common terminal use problems.

no prompt, or dead terminal

check the REMOTE button — it must be down
check the AUTO LF button — it must be up. This also causes spastic prompts
check the BLOCK MODE button — it must be up
do a hard reset if all these fail
if it still won't prompt, check that the TCS computer is still running.
- The RUN light should be on
- there should be other light activity on the front panel.
- If the RUN light is out, reboot the computer
if the computer is still running, try re-enabling the T.O. console
- go to the TCS Primary Computer system console, under the computer room window
- press the ENTER key, and get a "*" prompt. If you don't get a prompt, reboot the computer
- enter the following commands: (case doesn't matter)
  - RU,FMGR
  - CN,11,16
  - EX
- if this doesn't revive it, reboot the computer

terminal only uses a portion of screen width

the margins have become set

to reset an individual margin, move the cursor to where you want the margin using the cursor keys

press the CNTL key and the arrow key for the margin you want to set.

for example, to set the left margin, use the left arrow key to move to the far left of the screen. Then hold down CNTL and press the left arrow key again.

a hard reset is also a quick fix for this

terminal only uses a portion of screen height

the memory lock has probably been set

there should be a light to indicate MEMORY LOCK on, but some of the terminals don't have this

press the MEMORY LOCK button

the MEMORY LOCK light should go out

text should scroll up to the top of the screen

terminal operates slowly

the BAUD RATE may have been changed

turn the BAUD RATE knob to 9600

Logging on to the TCS

It is necessary to be logged onto the TCS software system to perform most of the procedures in these instructions, and other observing or setup instructions.

Already running?

If the system is already running, you do not need to log in. To determine if the TCS is already up, look at the channel 14 TV monitor:

if the normal display is present, and UT (universal time) is running, the system is up.
if the balance display is up, it is difficult to tell whether it is running or not. Try a command at the T.O. console.
if the display is not present, or UT is not changing assume the system is not up. Follow the next steps to log onto the system.

Log in prompt

At the T.O. station, on the HP 1000 terminal, press any key to get a prompt.
The prompt should be something like "TCS III Primary System:".
If there is no prompt, reboot the computer.

Log in

Type TCSIII to log onto the system.
Commands to the TCS can be in either upper or lower case.
The system will take at least one minute to initialize. Do not try to use the terminal until it prints "TCS III ready".
If these procedures are unsuccessful, try reboot the computer.

Entering TCS III commands

Working with an HP 1000 is a bit different than working with some more modern computers. However, it is not at all hard once you master a few of the differences.

User interface:

TCS uses the CFHT DILOG system, which was the main data acquisition user interface before PEGASUS was developed.

Almost all of the TCS operations are in a command driven mode. There are no menus or questions. You must typically know the commands to be used. While not very good for the novice, command driven systems are typically preferred by experts and frequent users.

Prompts:

Normally the TCS will not have a prompt on the bottom line of the screen. The cursor will simply be at the left margin.
It is necessary to have the "TCS III command" prompt on the screen before trying to type a command.
If you type before getting a prompt, a prompt will appear, and part of the command will be lost.
To get a prompt, press any key — the space bar is recommended.
When a prompt is present on the screen, this indicates the system is expecting a command to be entered. At this time, it cannot write anything to the screen. Keeping a prompt on the screen can cause tasks in the system to hang trying to write to the screen, and may even cause parts of the system to crash. It will certainly cause the hardware to shut down the telescope if error messages need to be displayed, and can't. DO NOT keep prompt lines on the screen longer than needed!
When a prompt is displayed, enter the command and press ENTER.

Execution:

Some commands may take a long time to execute, and may not give any feedback on the screen.
Wait a while before assuming the command did not work.
In general, don't enter a lot of repetitive commands without finding out what is going on.
In many cases, the system queues commands, and this can cause more problems.
Most commands eventually give some indication they worked, such as a display on the console.

Help

Help can be obtained with the extensive help system:

To obtain a list of all available commands (it will differ in different modes), use the ?? command.

As this is a dual purpose command, it may sometimes print an explanation of the last error message.

Just try again, and it will print a list of commands the second time.

To obtain additional help on any single command, just enter HELP commandname.

To get an explanation of the last error message, enter ??. or EXPLAIN. The explanation is whatever the programmer put into a text file when the program was written. The explanations range from the extremely helpful to the ridiculous.

To get an explanation of a previous error, enter EXPLAIN error_number, where error_number is the number which preceded the original error message.

Logging off the TCS

Normally the TCS III system is left running all the time. This is done so it can be accessed from data acquisition sessions. If you log off the TCS, be sure to check to see whether it is being used remotely. If possible log back on as soon as possible.

Get prompt

Get a prompt at the console, and enter /E.

Clear screen

Use the home key ( ) and CLEAR DISPLY key to clear the screen.

Troubleshooting the TCS computer

This section gives some quick checks and fixes for some common TCS computer problems.

Terminal problems

Look in the terminal setup instructions, in section above.

Computer self-check

The HP 1000 computer has a self-check which is run when the unit is powered on. These checks should be reserved for qualified technical staff. To run the tests:

Shut down disk drive
- The HP 1000 computer should not be powered off or on when the system disk drive is running.
- Turn off the Primary System Disk Drive by pushing the RUN/STOP switch to STOP
Open the front door of the computer with the key, located on the left side
Do not drop the front door! Do not let it fall!
Switch off the computer power with the large AC circuit breaker, which is located on the left side, at about mid-height.
If the computer has a large, white connector, with about 10 large wires, just below the power switch, check it for overheating. If it is very hot, call for help
Wait about 10 seconds, and re-power the computer.
Immediately close the front door, and watch the lights.
There should be activity in the display register lights, and the register select lights
When done, only the T-register light should be on
If the 16-bit display register lights are all on, and/or the register select lights are all on, the computer has failed the self-check
Obviously, if no lights come on, the stupid thing stay broke

Additional tests

The machine has several other tests which must be run by front panel sequences. They should be run when the computer integrity is in question.

FPP test

this tests the hardware floating point processor

store 105004 (octal) in the A-register

store 0 in the P-register

press PRESET

if the OVFL light remains on, the test has failed

press INSTR STEP

a 102077 (octal) indicates successful completion

FFP test

this tests the fast Fortran processor firmware

store 105200 (octal) in the A-register

store 0 in the P-register

press PRESET

press INSTR STEP

a 102077 (octal) indicates successful completion

SIS test

this tests the scientific instruction set firmware

store 105377 (octal) in the A-register

store 0 in the P-register

press PRESET

press INSTR STEP

a 102077 (octal) indicates successful completion

VIS test

this tests the vector instruction set firmware

store 105477 (octal) in the A-register

store 0 in the P-register

press PRESET

press INSTR STEP

a 102077 (octal) indicates successful completion

Booting problems

RUN light will not stay on

note: this stuff only applies to 7925 disk drives, which are no longer in use. Not sure of 7933 procedures, but believe should display RUN on the led's. They only have one or two control buttons, which are labeled something like LOAD.

check the Primary System Disk Drive drive power
- the unit should have a red "Drive 0" illuminated in the LED's on the front panel
- if the LED's are not on, check the power cables and circuit breaker at the rear of the drive.
DRIVE ERRORS
- if there is a "step =" in the LED's, push the "End" switch, on the left keypad, to clear this error. If it doesn't work, try the next step.
- if there is an error message in the LED's, push the "Load/Unload" switch to spin down the disk, and then press it again after about 10 seconds to spin it up again. The drive will go through a test cycle, and then should either say "Drive 0" or have a fail message. Try this several times if necessary.
- if all that doesn't work, try letting it spin all the way down, then back up. Also, spin it down, power it down with the back switch, and then spin it up. There is a manual on the left, back shelf in the computer room. It is possible to run a lot of diagnostics from the keypad.
- there is a junk drive, but with good electronics, down in the second floor inner coude electronics area. This is a source of spare parts. There should also be a spare interface card in the computer room, right, blue cabinet. If the diagnostics are very specific on suggesting a card to swap, it's worth a try. If they say media or head damage, give up on the drive
- it is possible to swap the primary and backup drives. This would be the right thing to do if you have a known dead backup computer and known bad primary drive. Do please turn off the computers and drives first. You may swap at the computers or at the HPIB connectors on the drives.
- if the drive makes gross mechanical noises (other than a medium pitched noise from bad spindle bearings), especially after the heads load, it has probably failed.
- if the drive cannot be made to work, consider switching to the backup system, and calling for help.
- do not, whatever, attempt to open the "lid" and remove the disk pack. Absolutely, totally, without fail, and don't even think of trying to swap packs between drives.
System starts, then no more activity
Perhaps something has taken over the system, and is blocking normal activity
- can you get a "*" prompt on the system console (in the computer room, under the window)?
- if not, there is probably a serious problem, such as hardware
- yes, the system has begun booting and is stuck
- Execute the system status command
  - at the "*" prompt, enter RU,WHZAT
  - this should give a list of programs which are active in the computer. Of course if nothing happens, there is some real problem!
  - in the middle of each line is a number representing the status of each program.
  - A status of 1 indicates the program is scheduled to be run.
  - A status of 3 indicates the program is waiting on some resource, or on another program.
  - If the GASP program is listed as a status 3,
    - wait about a minute, and then run WHZAT again.
    - if GASP is still in the same status, it can probably benefit from a quick death.
    - enter the command OF,GASP,1
    - hopefully the system will come to life
  - If some program is listed as a status 1,
    - run the WHZAT program several times in quick succession
    - if the same program is always listed as a 1, it may have gone into a tight loop (or crashed), and is hogging the computer
    - you should call for help on one of these, as other action may be detrimental

Booting the TCS computer

Occasionally the TCS III system will be dead, and you can not log into the system. It may also crash, or hang during operations. At this time the old-fashioned remedy of rebooting the computer may be the best bet.

Location

The TCS III primary computer is in the 5th bay in the computer room.
It is the topmost HP 1000 computer, and should be prominently labeled as the primary system.
The TCS III backup computer is located near the bottom of the same equipment bay.
The disk drives for the TCS computers are located to the far left of the equipment racks in the computer room. They are plainly labeled for the Primary and Backup systems.

Front panel sequence

In these procedures, the computer should be showing some signs of life, such as LED's on. If not, consider calling for help.
If the RUN light is on, press HALT. These are at the left bottom.
Use the REGISTER SELECT button to select the S register.
- This is the horizontal button in the center.
- It moves a light in the horizontal row of lights above it.
- The S register is the rightmost light.
- The idea is turn it (and only it) on. (If all the lights are on but one, a diagnostic mode has accidentally been engaged.
- Press the MODE (lower right) button to return to the normal mode.)
Use the switches below the 16-bit display register to set them so there are lights illuminated only where there are dots stuck to the panel above the lights. If there are not dots, then use the dot pattern on the backup computer, or vice-vera.
- Pressing the top of a switch turns on the light, and
- pressing the bottom turns it off.
- Match the lights to the dots, which are usually stuck to the front of the computer, right above the lights.
  - If there is only one set of dots, use it.
  - If there are two sets, use the one labeled 7933.
  - If there are no dots on either the primary or backup computer, use the dots on the other computer.
  - And, if there are no dots anywhere on either of the computers, try setting in an octal value of 141400.
- If a lot of lights are on to start with, use CLEAR to initially set them all off.
Press the STORE button (lower right).
Press the PRESET button (lower left).
Press the IBL button (lower left).
Press PRESET again.
Press the RUN button (lower left).

Boot completion

The computer should turn on the RUN and INTERRUPT SYSTEM lights, and show some action in the other lights.
Messages should start to scroll up the system console. This is one of the Wyse terminals under the window in the computer room.
The appropriate disk drive should show some activity. You may be able to hear or feel it jumping around, joyously loading the programs. You should also be able to see a "drive access" LED (unmarked, of course) blinking off and on.
It takes at least one minute for the system to come up. This will be indicated at the T.O. console by a message like "RTE 6/VM restarted - terminal 11", and at the computer room system console by "RTE 6 Welcom file operations completed".
There may be notes on either the front of the computer, or on the system console terminal, indicating specific problems with the computer, and giving instructions for some cures.
If the system does not come up after two or three tries, call for help before attempting anything.

Switching to the backup TCS computer

If there is an unrecoverable failure of the TCS primary computer, it is fairly easy to switch to the backup computer. However, do not do this without first checking with Waimea to make sure it is both the right thing to do, and it is OK to attempt the switch.

Stop the primary computer

It is not possible for both of the computers to run the TCS program at the same time. Normally you would log off the primary computer, to shut it down.
If you wish to rapidly switch back and forth between the systems for some type of checking, it is sufficient to just press HALT on the computer which is not being used.
Later, just pressing RUN will probably start it again.

Flip the R-Buss switch

It is located in a black panel between the TCS primary and backup computers.
It is clearly marked for primary and backup computers. Use these markings rather than any computer name markings.
TCS IV note:
- In order to switch computers you will have to reconnect the backup computer to the switch. There are two ways to do this - the first is preferred:
  - go behind the TCS computers. Take the R-Buss cable off the Primary computer and move it down to the same interface card slot on the Backup. The right connector is the very bottom connector. Please be very, very careful with it.

Switch the T.O. console

NOTE: it is not longer necessary to do this, as the terminal connection is made via the terminal server! However, it will be necessary to somehow access the backup port. Here are two ways:

Open another hpterm window on the OA console. If you want a big, scrollable window, you will have to go to a regular hpterm and enter "hpterm -sb -sl 1024 &". In that window type "telnet termsrv2 5010" (you may also try 5011). This should connect you to the backup.
you can try to find the cable for the primary computer on port 9 of termserver 2, then find the cable for either of the backup ports (10 or 11), and stick them in 9. You should then be able to access the backup computer from the usual TOS HP1000 screen.
At the terminal patch panel, one bay to the right, disconnect the T.O. console cable from the primary computer connector (lower left)
Connect it to the TCS backup computer connector which is two holes to the right.
The markings are not the best, and at least two people have worked on it, but it shouldn't be too hard to spot the right connectors.

Start the backup computer

The backup computer is typically left running. However, due to power glitches, failures, etc., it may have stopped.
Test the computer by checking the RUN light on the front panel. If it is out, the computer must be powered on and then rebooted
Go to the TCS Backup Computer system console, which is the left terminal on the table under the computer room window. Press ENTER. If you do not get a "*" prompt, the computer must be rebooted.

Log on to the backup computer

Go to the TO console, and press a key to get the log in prompt
The prompt should be "TCS III Backup System:", or at least it should have "Backup", or "Bak", or something to that effect.
If it is still for the primary system, the T.O. terminal has not been switched at the patch panel.
log onto the backup computer. Except for prompts which have "backup" instead of "primary", the procedures should be the same as above.

Backup computer status

The backup computer may be "behind" the primary computer in software revisions, and thus not contain any recent software upgrades in the primary computer. They were pretty well synched up in May of 1997, and again (but not completely) on 29 Aug 1997.
Certain TCS information will not be current in the backup computer. At least the following will be affected:
- the zero points for the present upper end will be those from the last time that upper end was run with the backup computer, or from when the backup computer was updated with the primary files. This may cause initial pointing problems if the differences are great.
- the pointing limits will be those from when the backup computer configuration was last updated. This can result in inappropriate restrictions, which may restrict pointing when it shouldn't be, or permit computer slewing into danger areas for long instruments. Pointing restrictions are displayed when first logging on, and can be reviewed later with the LIMITS command. Check them against the config board, or the current checklist. They can be changed in the balance program. You should get help on this one, as it is a bit obtuse.
- Certain systems have hardware links to the TCS primary computer, and thus will not run with the backup. They can be changed with a little connector swapping, but this should only be done if necessary for the particular system. They are all telephone type cables carrying RS-232 signals. They are located in the back of the HP 1000 cabinet, and go to harmonica type connectors. They are:
  - the touchpanel display of bonnette status
  - the HR Cam guider

Getting the telescope ready for operation:

These are the simple steps needed to make sure the telescope is set up for operation. They should be checked over before any attempts are made to move the telescope.

Make sure it is OK for you to be moving the telescope

during a setup day, check with TIC and get his/her permission
during normal days, check with the head daycrew person, and also with anyone else who might be working around the telescope
at night, only the T.O. may move the telescope. The T.O. must check with the observer and get their permission before moving the telescope.
make a preliminary check of the 5th floor

Get the TELESCOPE KEY

follow applicable safety procedures to remove it from the board.
Insert in the lock, and turn 1/4 turn to the right to enable the system.

Ensure telescope hydraulics are on, and pressure is OK

Normal pressure is 950 to 1050 PSI on the digital readout of TELESCOPE HYDRAULICS at the top of bay 6.
To turn telescope hydraulics on:
NOTE: this is no longer applicable as the Operations Goup has switched control down to the hydraulics unit on the first floor. Instructions are posted on the wall somewhere down there.
Press TELESCOPE HYDRAULIC STANDBY button in bay 6.
Wait about 5 seconds and press TELESCOPE HYDRAULIC ON.
Pressure should rapidly come into operating range.

Ensure air pressure is up, and OK

Normal pressure is 80 to 105 PSI, on the digital readout of MIRROR CELL AIR PRESSURE in bay 6.
Joy over 80 light should be on on the Betalarm panel.
Currently the air compressors are left running all the time. If this changes, you will have to enquire about the new proceedure for starting them. In the old days, the Joy compressor buttons near the top of bay 6 on the T.O. console directly controlled the compressors.

Ensure the telescope servo amplifiers are on

on Panel F (beside the main door to the control room) make sure the TCS servo amp green button (upper right) is on

Unlock the telescope

the ALPHA UNLOCKED and DELTA UNLOCKED buttons in the lower part of bay 6 must be lit.
the lights being on simply indicate that the unlocking system has been activated. They do not indicate anything about the actual pin position.
press the buttons if they are off.
when the locking pins withdraw, red LOCKING PIN lights should come on on the status panel in bay 5. This is the position indication of the pins, and comes from switches on the pins.
the telescope encoders reset when the pins are withdrawn. This will cause error messages on the TCS console.

Simple telescope operations

Here are some simple steps for operating the telescope in computer mode, which is now most work is done.

Prepare the telescope

All of the steps in the Preparing the telescope for operation section, above, must be accomplished successfully before trying to move the telescope.
The TCS computer must be running the TCS III software.
the console should give a message indicating "computer active".

Put the TCS in computer mode :

press the COMPUTER ACTIVE button in the bottom of bay 6
IF the button lights up, the system is in computer mode. Reasons for not lighting are:
- the TCS is not running. Log onto the system.
- a prompt line has been left on the TCS console. Press ENTER to clear the prompt.
- the R-Buss switch is selected to the wrong computer.
- the TCS hardware has malfunctioned.
the console should give a message indicating "computer active".

Safety check:

physically inspect the 5th floor for safety concerns
- either do this yourself, or direct someone to do it. In any case, you are responsible for the telescope and personnel safety.
- Do not move the telescope based on a report from someone who was on the 5th floor, unless that person has made a deliberate inspection solely for the purpose of moving the telescope. Simply having come from the 5th floor is not sufficient.
- look at the area under the telescope, considering how far it will be moved.
- look overhead for people working on the dome or telescope
- check that the access cage is down
check that no safety tags are on the board.
- if there are, check with the person who placed the tag during the day
- at night check with the telescope operator, and together decide whether it is safe to remove the tag and move the telescope.
make an intercom announcement saying "the telescope will be moving".

Enter the position to slew to

hour angle

To slew to an hour angle position (relative to the telescope mount)

enter HA hh:mm:ss.s DEC dd:mm:ss.s
you may omit leading zeros in any position
you may enter a single 0 in any position
you may omit the fractions of seconds.
some valid positions are:
- HA 0 or HA 0:0:0 or HA 00:00:00.0 for straight up
- HA -3:0:0 or HA -3:0:0 or HA -03:00:00.0 for 45 degrees east
- PARK for normal zenith parking position
you may separate the HA and DEC with a space, several spaces, a comma, or a comma and some spaces. It is very free format
you may put the HA and DEC on separate lines. If you only change one, the other remains the same.
you may check the current slew target by commanding HA DEC without any parameters. The system will print the positions it will slew to.

right ascension

To slew to a right ascension position (relative to the sky)

verify that the system equinox, displayed at the top of the channel 14 monitor is correct
if the equinox is incorrect, set it with the EQ nnnn command
when observing catalog stars, either SAO or with the STAR command, the equinox is set automatically.
enter RA hh:mm:ss.s DEC dd:mm:ss.s
follow the same rules as for HA coordinate entry, above

Initiate the slew :

enter GO to start the telescope slewing
it will take several seconds for slewing to actually start
the computer checks many things before trying to move. This may result in error messages. Typical problems are:
- the system is not in computer mode. Press COMPUTER ACTIVE and try again.
- the key switch is not on. This is not reported very well, but is something to check if you get an obscure failure message.
- the standard system glitch has caused one or both axes to fail to release their brakes. Press, in order, SERVO CLEAR and COMPUTER ACTIVE to reset the error.
the telescope should start moving. This is a critical time, as any problems typically show up on the first slew. Keep a close eye on the following systems for the first few seconds:
- watch the drive current meters at the top of bay 5.
  - They should twitch a good bit, perhaps even going way into the yellow, before they sort of settle down in the green area.
  - If the keep going steadily into the red, or if they peg in the red, something isn't moving. Hit the big, red EMERGENCY button, in bay 5.
    - check for locking pins still in
    - check for hydraulics off on the alpha axis
    - check for broken things under the telescope. (Make note to look for new job!)
- During a normal slew, the current meters might increase a bit as you get away from straight up, due to the slight bottom heaviness of the telescope. They will decrease about the same amount on the way back to zenith.
- listen to the audio feedback tone.
  - it should increase smoothly in pitch until it reaches slew speed.
  - rapid changes in pitch represent hard accelerations of the telescope, usually accompanied by large currents and broken objects.
  - Hit the big, red EMERGENCY button, in bay 5.
- If the telescope is slewed too close to the horizon (below 12 degrees), the system will reduce the slewing speed. This causes a distinctive stepwise, change in the audio sound. This should not be confused with the sound of a sudden stop.
- watch the digital axis velocity readouts in bay 5
  - the readout should increase smoothly up to the slewing speed
  - the present maximum computer slew speed is 2200 arcseconds per second for both axes.
  - the readouts will decrease as the telescope is slewed beyond 12 degrees from the horizon.

Stopping the telescope

There are several ways to stop the telescope when slewing. They are listed in reverse order of preference — try to stay away from the bottom of the list.

normal completion

simply let the system complete the commanded operation.
If this is not where you want to go, it may not take much longer to let it go and then command the right position, than it would do stop first.

STOP command

issue the STOP command to stop the slew.
The telescope will overshoot and then come back to the position where STOP was issued.
You may then enter a new position, or perform other commands.

emergency stops :

The only other means of stopping the telescope should not be considered normal operating procedures. They should reserved for use in case of an imminent equipment or personnel crisis, and then only to prevent damage or injury to equipment or personnel.
When there is no clear equipment or personnel emergency, do not use these emergency stop methods. They cause severe loads on the brakes and gear boxes, and thus should not be considered normal operating procedures.
the ABORT command at the TCS switches the system to manual mode, and applies the brakes.
The red EMERGENCY pushbutton in bay 5 switches the system to manual mode, and applies the brakes.

Simple manual mode telescope operations

These are some simple steps for operating the telescope without using the computer. This mode is mainly used for dire emergencies.

Prepare the telescope

All of the steps in section above must be accomplished successfully before trying to move the telescope.

Safety check :

All of the steps in section , above must be accomplished before starting to move the telescope.

Get the TCS out of computer mode :

press either the SERVO CLEAR or INITIALIZE pushbutton at the bottom of bay 6.
the COMPUTER ACTIVE button in the bottom of bay 6 should be out
if the system was in computer mode, switching to manual will cause the console to give a message indicating "manual control".

Put the system in manual slew mode:

the MANUAL SLEW MODE button is in the bottom panel of bay 6, in the top row, near the T.O. handset pushbuttons.
the MANUAL SLEW MODE button must be lit for manual slew mode. Depress the pushbutton, if needed, to light it.
set the MANUAL SLEW VELOCITY knob, also near the T.O. handset pushbuttons, to line up with the maximum speed mark on the panel.
when in manual slew mode, the center button on the T.O. handset, or on a handset plugged into the T.O.'s handset receptacle, acts as a slew mode button. It loses its normal function as a Setting Mode select button.
pressing the center button the first time will initialize the TCS
- brakes are released
- servo amps are turned on
- slew mode is engaged
releasing the button exits slew mode
- tracking mode is engaged
- do not release the button at high speeds (> 200 arcsec/sec) as it causes excessive currents in the servo amps
pressing the button again switches back to slew mode

Slew the telescope

put the system into manual slew mode by pressing the center handset button
press the handset button for the direction(s) you wish to slew. Initially, it may be easier to move one axis at a time.
the telescope starts moving. This is a critical time, as any problems typically show up on the first slew. Keep a close eye on the following systems for the first few seconds:
- watch the drive current meters at the top of bay 5.
  - They should twitch a good bit, perhaps even going way into the yellow, before they sort of settle down in the green area.
  - If the keep going steadily into the red, or if they peg in the red, something isn't moving. Hit the big, red EMERGENCY button, in bay 5.
    - check for locking pins still in
    - check for hydraulics off on the alpha axis
    - check for broken things under the telescope. (Make note to look for new job!)
  - During a normal slew, the current meters might increase a bit as you get away from straight up, due to the slight bottom heaviness of the telescope. They will decrease about the same amount on the way back to zenith.
- listen to the audio feedback tone.
  - it should increase smoothly in pitch until it reaches slew speed.
  - rapid changes in pitch represent hard accelerations of the telescope, usually accompanied by large currents and broken objects. Hit the big, red EMERGENCY button, in bay 5.
  - If the telescope is slewed too close to the horizon (below 12 degrees), the system will reduce the slewing speed. This causes a distinctive stepwise, change in the audio sound. This should not be confused with the sound of a sudden stop.
- watch the digital axis velocity readouts in bay 5
  - the readout should increase smoothly up to the slewing speed
  - the present maximum computer slew speed is 2200 arcseconds per second for both axes.
  - the readouts will decrease as the telescope is slewed beyond 12 degrees from the horizon.
- DO NOT release the center button while slewing at speeds 200 arcseconds/second. If you need to change speed or stop, do one or more of the following:
  - release the button for the axis. The speed on that axis will gradually ramp down and come to a stop.
  - release the button for the direction the telescope is slewing, and press the opposite direction button. The telescope will rapidly decelerate, and start slewing in the opposite direction.
  - turn down the MANUAL SLEW VELOCITY knob. This will slow the slew speed of both axes.

Move to the target:

when you get near the target position, slow down using the velocity knob, and try to get near the target
release the center handset button when both axes are below 200 arcsec/sec.
you will not be able to achieve exact positions with the crude level of control in manual slew mode.
To move in on a target:
- exit manual slew mode by turning off the MANUAL SLEW MODE pushbutton
- the center handset pushbutton now acts like a SET/GUIDE switch
- use setting and guiding rates to accurately position the telescope to the target.

Considerations on using Manual Mode :

Please remember that in manual mode the layer of protections offered by the TCS III software is totally absent. There is a lot more freedom, and therefore potential to seriously damage things. Note the following considerations.

safety

there are no checks made for nearness to horizon. The telescope will run at full speed everywhere
there are no checks made for any of the limits. The telescope will run at full speed until it engages a limit
there are no checks made for long instruments. The telescope will run at full speed until it engages the long instrument limit (if installed). It may actually run over the limit, and continue slewing in the same direction. Use extreme caution when running in manual mode with a long instrument.

operational

the console LED position readouts (they don't work anymore, anyway!) are not corrected for refraction or pointing errors. This makes finding objects very difficult.
if possible, use a computer to process the star positions and give the telescope positions which correspond to them.
if using a TCS computer in conjunction with manual mode, the TCS hardware will have a "brakes-on" occurrence in the computer crashes, even when running in manual mode. This is a genuine feature! In might work better if the R-Buss switch is switched away from the computer, if it crashes frequently.
the tracking rate is not very good, and absolutely cannot be adjusted.
there are no amenities like autoguiders, star catalogs, etc.

Telescope limits

Typically one does not have to deal with the limits on a regular basis. However, on occasion the limits may become activated, and it will be necessary to clear them. The following material is from an older paper on the limit system, and should provide all the needed information.

This section is intended to clarify the present travel limit switches and indicators in use on the telescope and at the operator's console, and to define the proper response to any limit indication. It is recognized that the limit system is inadequate, and hoped that these indications can be improved in the near future. If that occurs, additional memos will accompany the changes. It should also be noted that the limit nomenclature used here is the currently accepted means of identifying the various parts of this system. Past nomenclature often resulted in confusion about the functions of the system, and will no longer be used.

End of axis travel limits

Each telescope axis has limit switches at each end of its travel to prevent mechanical damage to the telescope. In fact, there are two sets of switches at each end of travel. These are called:

hard limits :

These switches are the final electronic safety feature before metal touches. They will activate at approximately +/-6:30 hours in HA, and +98 and -58 degrees for DEC.

When a hard limit switch is activated, it brings the system to the manual mode with brakes on from any mode: — computer or manual, slew or track. It also illuminates one of the N, S, E, or W limit LED's on the console status panel.

The computer console will display a brakes applied message, but probably nothing else to describe the condition.

It should not be possible to move farther in the direction of the limit in either computer or manual mode.

To get off the hard limit, one must set the system for manual slewing, dial in a moderate slew speed, first press the handset button necessary to get off the limit, and then press the center button to initiate slew mode. This may take several tries, with resets necessary between tries.

soft limits :

These switches are just before the hard limits (about 2 degrees), and should be the ones which get activated first in any limit situation. They were added, as an afterthought, during the telescope integration, and thus are implemented quite poorly.

When any of the soft limits are activated, they illuminate the 8 degree limit LED on the console status panel. When slewing, the soft limits cause the telescope to drop into track. If this occurs at high speed, the system usually shuts down with an over acceleration LED indication on the console.

When operating in tracking mode, the soft limits should have no effect on operation. It is thus possible to continue observations after a soft limit has been hit.

They cause an 8 degree limit message to occur on the TCS terminal, if the computer is operating. As these limits are not handled separately in the system, there is no way of telling which limit is activated (or whether it is a real 8 degree limit or a long instrument limit).

It is possible to initiate a computer slew while in a soft limit situation. That slew can either get the telescope off the limit, or cause it to go farther into the limit.

Horizon limits

Because the telescope can take the primary mirror beyond vertical in some orientations, before hitting an axis limit, the caisson central is equipped with two horizon limit switches. These are ball in cone devices, with a specific angle to the cone where the ball will roll out and activate the limit.

These limits are:

3 degree limit :

8 degree limit :

Long instrument limits

Because some instruments mounted at cass can be long enough to hit the hour angle axis structure, it is necessary to have a system of additional, temporary limits to protect these instruments. This is done by placing ramps on the DEC drive gear, and having them activate a limit switch. This switch is wired in parallel with the 8 degree limit system, just as the axis soft limits are. Because of this, a long instrument limit indication is indistinguishable from an axis soft limit or an 8 degree limit.

Response to limit indications

Limit indications can indicate many problems with the telescope or the control system. They are intended to be the final protective systems to avoid catastrophic damage to the telescope or instruments. They must not be ignored. The following guidelines should help define appropriate action to take for various limit indications.

8 degree limit transient activation :

These indications, which occur quite infrequently, are best ignored. They are probably due to electronic glitches. Hopefully a rebuild of the General Control Card — unfortunately several years hence — will fix this problem.

8 degree limit constant activation :

The cause of this indication can be one of several things:

end of axis soft limit switch depressed
8 degree horizon cone limit switch activated (ball ran out of the cone)
long instrument switch contacted a long limit ramp

Response to this indication is dependent on the status at the time the limit situation is encountered:

Tracking an object:
Slewing to a target:
- encoder malfunction, making the computer think the telescope is actually in a safe position. The computer then slews the telescope based on the erroneous encoder position. In these cases, the encoder displays will appear quite normal.
- long instrument ramps installed, but computer set up for a wider limit range. Thus the computer slews at full speed into the limit switches. This occurs at declinations of about +73 and -37 .
- computer software malfunction, which hopefully can't happen. In this case, one of the encoders would display an extreme value, near the hard limit values presented above. If the actual 8 degree cone switch activates, the airmass will be greater than 6.8.
A physical examination of the telescope must be made in all cases when a steady 8 degree limit indication occurs while slewing. Verify that both axes are approximately where their encoders indicate. Inspect the HA hard stops to see if they have activated the soft limits. See if the DEC tube is near either of the hard stop bumpers. Look at the east side of the DEC gear for the long instrument ramps, to see if they are activating a switch.
Based on this examination, take the appropriate action:
on end of axis soft limit, incorrect encoder position:
The system hit the limit due to improper encoder position. The system must not be operated in computer mode until the encoders are reset. With an observer in the dome, slew the telescope manually to the zenith, and locate the zenith switches. Before proceeding, record the position readout of the bad encoder. Then insert the locking pins. This should reset the encoders. Perform two short ( 20 ) slews and return to the zenith. If the zenith switches come on, resume operations. If they don't, there is an encoder malfunction, and observations must be suspended until a repair is made. Record all incidents of encoder errors on the night report.
on end of axis soft limit, correct encoder position:
If it is actually on a soft limit, and the encoders correctly indicate this, command a computer slew to bring it to the zenith. Ensure that it slews to the zenith by either physical examination or proper operation of both of the zenith switches. If this all works OK, resume normal operations. Attempt to avoid a repetition of the incident. Report the incident on the night report. Try to record any circumstances which led up to engaging the limit, so a diagnosis can be attempted.
on long limit ramp, incorrect encoder position:
The telescope hit the limit because the computer is using erroneous positions. The telescope must not be operated in computer mode until the encoders are reset. Follow the procedure given above for recovering from an end of axis limit caused by incorrect encoder readings.
on long limit ramp, correct encoder position:
If the telescope safety code is 0 these ramps should not be installed. It is possible to use the TCS command LIMITS to have the system print the limits it is currently using. If the ramps are installed, and shouldn't be, call the Operations group supervisor to get permission to remove the ramps. Always remove both ramps to avoid confusion later.
If the ramps should be installed, then the TCS software limits are set wrong — otherwise it would have inhibited the slew. Inform the observer that his object is outside the telescope limits, and that the observation is not possible. Report the problem on the night report, and take care to not slew into the limits again. The daycrew will install the correct software limits the next day.
none of the above:
There is one other possible cause — a malfunction in the limit system. This must be considered only as an extreme last resort. The Electronics and Operations supervisors must be consulted, and decisions will be made on how to proceed with a solution or workaround for the problem.

3 degree limit constant activation :

This means the 3 degree limit LED is fully illuminated. There was probably a brakes applied message, with no other information, on the terminal.

The cause of this indication should only be the 3 degree cone limit switch becoming activated. This should happen at an airmass of about 13.3, and the telescope must be at extreme hour angles and very southern declination. Also, for this to happen, the telescope should have gone beyond the 8 degree limit, and it should also be illuminated. If it isn't, report it as a malfunction.

It should not be possible to engage the 3 degree limit while slewing the telescope under normal conditions. The protections — most of which rely on correct encoder positions — are basic telescope limits, possible restricted limits, elevation limits, and the 8 degree limits.

Reasons for encountering a valid 3 limit are:

tracked into the 3 degree limit after encountering the 8 degree limit. Probably due to over zealous observers. Recover from the limit, using ordinary, manual mode procedures, and don't do it again. Point out to the observers that this is considered bad practice, and has to be reported as an incident on the night report.
encoder malfunction, in conjunction with a failure or hardware overrun of the 8 degree limit switch. An encoder failure makes the computer think the telescope is actually in a safe position. It then slews the telescope based on this information. Either the 8 degree limit failed and didn't stop the slew, or the system kept going too far after it dropped out of slew, and hit the second limit (unlikely).
encoder malfunction, in conjunction with an operator override of the 8 degree limit switch. An encoder failure makes the computer think the telescope is actually in a safe position. It then slews the telescope based on this information. When the 8 limit is hit the operator, believing the erroneous telescope displays, commands the system to continue slewing to the target. Because of design flaws in the hardware and software, the system permits this. If 8 degree limit procedures (above) are followed, this won't happen.
computer software malfunction, which hopefully can't happen.

The first response to this very serious indication is to make a physical inspection of the telescope to ensure it is in the reported position, and that no damage has been done. Based on this examination, take the appropriate action:

at 3 degree limit, incorrect encoder position:
The system hit the limit due to improper encoder position, after having gotten past the 8 degree limit. The system must not be operated in computer mode until the encoders are reset. With an observer in the dome, slew the telescope manually to the zenith, and locate the zenith switches.
It may be impossible to get off the 3 degree limit with certain encoder malfunctions. Before proceeding, record the position readout of the bad encoder. Then insert the locking pins. This should reset the encoders. Perform two short (20 deg) slews and return to the zenith. If the zenith switches come on, resume operations. If they don't, there is a persisten, recurring encoder malfunction, and observations must be suspended until a repair is made. Record all incidents of encoder errors on the night report.
at 3 degree limit, correct encoder position:
It is actually on a hard horizon limit, and the encoders correctly indicate this. The first action is to manually get the telescope off both the 3 degree and 8 degree limit switches in manual mode. Then command a computer slew to bring it to the zenith. Ensure that it slews to the zenith by either physical examination or proper operation of both of the zenith switches. If this all works OK, resume normal operations. Attempt to avoid a repetition of the incident. Report the incident on the night report. Try to record any circumstances which led up to engaging the limit.
none of the above:
There is one other possible cause — a malfunction in the limit system. This must be considered only as an extreme last resort. The Electronics and Operations supervisors must be consulted, and decisions will be made on how to proceed with a solution or workaround for the problem.

axis end of travel hard limit constant activation :

This means one of the axis limit LED's is fully illuminated. There was probably a brakes applied message, with no other information, on the terminal.

The cause of this indication should only be one of the axis end of travel hard limit switch becoming activated. This should happen at an hour angle of about six hours, thirty minutes, or a declination of +98 or - 58 degrees . Also, for this to happen, the telescope should have gone beyond an axis soft limit indication, so the 8 degree limit should also be illuminated. If it isn't, report it as a malfunction.

It should not be possible to engage the axis hard limits while slewing the telescope under normal conditions. The protections — most of which rely on correct encoder positions — are basic telescope limits, possible restricted limits, elevation limits, and axis soft limits.

Reasons for encountering a valid axis hard limit are:

tracked into the hard limit after encountering the soft axis limit, which is indicated as an 8 degree limit. Basically due to over zealous observers. Recover from the limit, using ordinary procedures, and don't do it again. Point out to the observers that this is considered bad practice, and has to be reported as an incident on the night report.
encoder malfunction, in conjunction with a failure or hardware overrun of the axis soft limit switch. An encoder failure makes the computer think the telescope is actually in a safe position. It then slews the telescope based on this information. Either the soft limit failed and didn't stop the slew, or the system kept going too far after brake application and hit the second limit (unlikely).
encoder malfunction, in conjunction with an operator override of the soft (8 degree) limit switch. An encoder failure makes the computer think the telescope is actually in a safe position. It then slews the telescope based on this information. When the soft limit is hit the operator, believing the erroneous telescope displays, commands the system to continue slewing to the target. Because of design flaws in the hardware and software, the system permits this. If 8 degree limit procedures (above) are followed, this won't happen.
computer software malfunction, which hopefully can't happen.

The first response to this very serious indication must be to make a physical inspection of the telescope to ensure it is in the reported position, and that no damage has been done.

Based on this examination, take the appropriate action:

at a hard limit, incorrect encoder position:
The system hit the limit due to improper encoder position, after having gotten past the soft (8 indication) limit. The system must not be operated in computer mode until the encoders are reset. With an observer in the dome, slew the telescope manually to the zenith, and locate the zenith switches. Note that it may not be possible to get off the hard limit under certain combinations of limits and encoder errors. Before proceeding, record the position readout of the bad encoder. Then insert the locking pins. This should reset the encoders. Perform two short (20 deg) slews and return to the zenith. If the zenith switches come on, resume operations. If they don't, there is an encoder malfunction, and observations must be suspended until a repair is made. Record all incidents of encoder errors on the night report.
at a hard limit, correct encoder position:
It is actually on a soft limit, and the encoders correctly indicate this. The first action is to manually get the telescope off both the hard and soft (8 deg indication) limit switches in manual mode. Then command a computer slew to bring it to the zenith. Ensure that it slews to the zenith by either physical examination or proper operation of both of the zenith switches. If this all works OK, resume normal operations. Attempt to avoid a repletion of the incident. Report the incident on the night report. Try to record any circumstances which led up to engaging the limit.
none of the above:
There is one other possible cause — a malfunction in the limit system. This must be considered only as an extreme last resort. The Electronics and Operations supervisors must be consulted, and decisions will be made on how to proceed with a solution or workaround for the problem.

Exceptions

The limit system is designed to protect the telescope from physical harm during all operations. It is normally not intrusive on operations. Limit conditions are advertised in the Observers Handbook. If these procedures impede observations, permission must be obtained from one of the Directors, or the Chief Engineer to deviate from these rules. This permission should only be granted in cases where it can be conclusively demonstrated that the observations can be performed in safety. Any tests of equipment clearance must be performed at very slow speeds, in manual slew or track mode, and with observers in the dome watching closely for interference. Dome lights must be fully on for these tests. In no case will the axis end of travel hard limits, or the 3 degree horizon limit be bypassed in any fashion.

If the limit system flagrantly inhibits valid observations, then the system should officially be reevaluated. I do not believe this is the case. Until that occurs, the limit system should be considered the final arbiter of safe telescope operations.