>
User's Guide for the UH 8K CCD Mosaic Camera
G. A. Luppino, Mark Metzger
Revised: September 5, 1996
A PostScript version of this document is available.
The UH 8K CCD Mosaic Camera was designed and built to be
used at the CFHT prime focus and occasionally at the UH 88-inch f/10
focus. The camera was built at the University of Hawaii,
Institute for Astronomy Detector Laboratory by Metzger, Luppino
and Miyazaki (see Metzger et al. 1996, PASP, submitted) in 1995 and saw first
light at the CFHT in March 1995, and on the UH 88-inch in Aug 1995.
The camera is now available to observers at the CFHT and UH
88-inch telescopes. This document describes the instrument and
serves as an observer's manual.
The remainder of this section lists the global properties of the
instrument.
- Array dimensions and architecture: 8192x8192 pixels (15
m
pixels) 2x4 array of 4096x2048 CCDs.
- Gaps: top-to-top
20 pixels, side-to-side
50 pixels.
- Image scale: CFHT 0''.21/pixel, UH 88-inch 0''.13/pixel
- Gain: varies with CCD - typically 2
/ADU
- Readout noise: varies with CCD - chips (0,1,6,7) 5-10 , chips
(2,3,5,4) 15-20
- Operating temperature: -70
C - set with temperature controller
on dewar. Relatively high operating temperature is required to
achieve acceptable charge transfer levels.
- Dark current: varies with CCD - worst is chip 4 ( 0.5
/s). Dark current has a distinct pattern on some of the chips.
Dark frames are absolutely necessary.
- LN
hold time: 
24 hr - but in normal operation, dewar
should be filled in the evening before starting observing and again in
the morning.
- Readout time: 7 min full frame, 2 min binned
2x2.
- Data format: images written as 8 separate FITS files with data
written as unsigned 16-bit integers. The active area of each CCD
is 2048x4096 pixels but each CCD files is written as a
2080x4128 pixel image
with extra pixels in the serial (x) and parallel (y) directions
useful for determining the bias level.
- Filters: Presently V, R and I are available. The instrument is
equipped with a 2-position filter slide.
- Shutter: The shutter is a ``guillotine'' type with two
blades that move in the same direction for opening and closing, thus
providing uniform exposures across the array even for relatively
short exposure times.
- Log into data acquisition computer (hostname: stego):
login: obs
passwd: *****
From some window, type
% setenv OBSERVER "Name for FITS"
% mosaic
at the unix prompt. This will start the
data acquisition program mcdcom. This is a command-line
driven program written by Mark Metzger. Communication with this
program is done through the upper left shell window.
Upon starting mcdcom for the first time (or after re-starting), issue the following
set of commands:
> mosaic full
> filter 0
> fp name. [sets the prefix name - use the dot]
> fn number [sets the frame number]
> cd data_directory
These commands are described in detail in the next section.
MCDCOM COMMANDS
cd directory Sets working directory where data will
be stored. This will need to be changed
periodically during the night as disk
partitions fill up with images.
? Lists mcdcom commands and syntax.
mosaic full Downloads DSP code to CCD controller to
read out the complete mosaic -- unbinned.
The command should be executed whenever you
first enter the program or whenever the
controller electronics are reset (e.g. by
hitting the reset buttons or power cycling).
mosaic bin Downloads code to read full CCD mosaic binned 2x2.
mosaic bin4 Downloads code to read full CCD mosaic binned 4x4.
mosaic focus Sets up for focus sequences. Downloads code
to read out the top half of chip 1
(2048 x 2048 unbinned).
mosaic find Sets up for reading out top half of chip 1
binned 2x2. Only 30s readout time.
object inttime name Sets up normal exposure for an OBJECT.
Sets integration time to inttime.
flat inttime name Same as object, but enters FLAT keyword into
header.
dark inttime name Sets DARK keyword. Disables shutter operation.
clear Flushes (erases or clears) charge from the
CCDs. Must be executed before a set of
focus plate exposures (see below).
go Initiates the exposure. ``go'' does different
things depending on the mode (e.g. object
or focus).
For example, go will do following:
if ``object'' mode:
- erase (or flush) CCDs
- open shutter for inttime seconds
- readout CCDs
if ``focus'' mode (see below):
- open shutter for inttime seconds
go n Takes n consecutive exposures.
focus inttime name Mode for doing ``focus plates''. Observer
must first clear the CCDs using ``clear'',
then each time ``go'' is typed, the
shutter will open for inttime seconds.
Between exposures the observer should
adjust the focus by some increment, and
offset the telescope (by, say 10 arcsec).
When the desired set of exposures are
completed, the observer types ``rm'' to
read mosaic manually (although only the
top half of chip 1 will be read out).
Cntl-C Interrupts an exposure. Observer can
then manually readout the CCDs (rm),
resume exposure (go), or abort exposure
(simply flush the CCDs with clear and
start over).
et inttime Will change the exposure time (e.g. you
can modify the desired exposure while
within a paused state). Time is in seconds.
fn frameno Sets CCD frame number (note: current frame
number is always shown in the prompt).
fp name. Sets frame prefix name. Files are written
out as 8 separate FITS files:
name.frameno.0
name.frameno.1
.
.
.
name.frameno.7
filter n Changes filter slide to filter 0 or 1.
Note: upon reset or power cycling, the
filter slide will reset to position 1
but the computer will not know this.
After reset, explicitly set filter
telescope [command] Send telescope command or
display current TCS information.
status Displays CCD readout status (e.g. binning,
readout type, frame size, etc.).
wf [file] Manually write file to disk. This is
needed of you run out of disk space while
writing to disk. The image is not lost,
it is stored in memory. You can change
directory within mcdcom (cd),
and then write the file out in the new
directory using wf. Note there may remain
a partially written set of files with the
same name in the old directory.
source script [line] Will execute a set of commands listed
in file script. Useful for doing darks.
OTHER COMMANDS (output of the help ? command):
----------------------------------------------
quit Quit
diag command [args] Access diagnostics
ii Re-init I/O
device n Set current I/O device to #n
sync Resync communications
ll 'file' Read DSP code .lod file
dl Download DSP code
pl Print DSP code
df 'file' Read DSP file and download
dm Download full mosaic code
rm read mosaic
rc [Xnx Xny] read CCD
iraf Toggle IRAF output format flag
idle Put camera in idle & recalibrate
ep seconds Set precise exposure time
set var [val] Set variable
unset var Unset variable
clear [num] Clear (wipe) CCD
sf Set format of CCD readout
auto Set automatic action
name objname Set object name
comment comment Set comment in FITS header
shutter (open|close) Command shutter
bias Setup for bias
comp Setup for comparison
sound Toggle fancy sounds
drift Do drift scan
video [recd] Shutterless Video
vexpose [exp] Set video time
utility cmd [addr [value]] Send utility board command
istat Compute simple statistics
The CCDs are read out as 8 separate FITS files with suffix 0-7.
Their relation to each other in the focal plane is shown below.
8K MOSAIC LAYOUT
|------*|------*|------*|------*|
| | | | |
| | | | |
| 2 | 3 | 5 | 4 |
| | | | |
| | | | |
| | | | |
|-------|-------|-------|-------|
| | | | |
| | | | |
| 0 | 1 | 7 | 6 |
| | | | |
| | | | |
| | | | |
|*------|*------|*------|*------|
* ==> readout amplifier => pixel (0,0)
Note: When displayed separately, chips 2,3,4,5 will appear
``upside down'' as compared to chips 0,1,7,6.
There is only limited quick-look capability. The observer must avoid
trying to do too much on stego during an observing session. If too
many memory intensive processes are running, the camera may
lose data during a readout. It IS safe to have a few windows open,
and to be writing data to one or both tape drives. However,
it is NOT SAFE
to launch an IRAF session or run SAOimage, for example. If possible, it
is preferred that the observer use another computer (e.g. wiki
at CFHT) to look at the data using her/his favorite
display tool (e.g. SAOimage). The files can
be ftp'ed to the wiki disk or, preferably, the stego
disks are crossmounted onto wiki (the usual situation).
If it is not possible (or very inconvenient) to inspect the data
on another workstation, it is possible to do limited analysis
on stego using the program mora.
mora is
started by typing mora at the unix
command line and then commands are issued within
the program environment. Images are read into buffers (at most,
only two buffers should be used to keep memory use to a reasonalble
level) and operations are performed on these buffers
(e.g. arithmetic, display, psf analysis, etc.).
A limited set of useful commands are listed below:
Brief summary of MORA commands:
? Lists mora commands and syntax.
rd 1 filename us Reads fits file into buffer 1.
us flag ensures data is read in
unsigned format.
cvt 1 1 r4 Converts buffer 1 to r4 -- needed for
interactive photometry to measure
seeing.
tv 1 lo high [flag] Displays buffer 1. Stretch will be
linear between lo and high unless
flag specifies an alternative
stretch (e.g. sqrt or log).
iphot Allows interactive measurements from
image displayed by tv. Must be in r4
format. The following commands are
useful (cursor must be in image
display):
x (prints stats of star --
psf is lower left number
[you may need to toggle the
mode]).
1 2 (prints stats in box defined
by pressing 1 at upper left
corner and 2 at lower right
corner).
? (prints list of commands).
e (exits iphot)
OTHER COMMANDS (output of the help ? command):
----------------------------------------------
history <> Show History
rfits <buf filename> Read FITS file
wfits <buf filename> Write FITS file
cd <dir> Change directory
ls <[opts]> List files in current directory
% <command> Execute shell command
@ <macro [opts]> Execute macro
end <> End macro
echo <[on|off]> Macro echo
cvt <buf1 buf2 conv> Convert type
create <buf typ size=nx,ny> Create blank buffer
buflist <[buf]> List buffers
head <buf> Show FITS header
fedit <buf [field code data]> Edit header entry
rm <b1 [b2...]> Remove buffers
copy <b1 [b2] [opts]> Copy buffer
box <[box# [x1 x2 y1 y2]]> Show/set box
aimage , si, mi, di <b1 b2 [b3]> Image arithmetic
aconst , sc, mc, dc <b1 [b2] const> Image arithmetic
trans <b1 [b2] [sqrt] [box=] > Transcendental functions
stat <buf> Image statistics
hstat <buf [opts]> Image histogram
debias <b1 [b2] [opts]> Debias image
flat <b1 b2 [b3] c1=x [opts]> Flatten b1 with b2
shift <buf nx ny> Offset image
tv <buf [range] [opts]> Display image
mark <> Mark image
psf <buf [opts]> Create PSF
genpsf <buf> Generate artificial PSF
iphot <> Interactive photometry
cscale <buf bufref [opts]> Scale one image to another
czap <buf1 ... bufn [opts]> Zap bad pixels in scaled image set
cadd <buf1 ... bufn bufd [opts]> Add scaled zapped images
cmed <buf1 ... bufn bufd [opts]> Median scaled zapped images
clip <buf [bufd] [lo=X] [hi=X] [band]> Clip data in image
filter <b1 bfilt [b2] > Filter image
map <b1 [b2] [box=] [boxd=] > Map image
mapmos <b1 [b2] [box=] [boxd=] [bb] map=> Map mosaic
quit <> Quit
The observer can write images in any
/local/uh8k* partition (/local/uh8k1, /local/uh8k2, ... /local/uh8k10).
Each partition is 1.9 Gbytes. At CFHT, these directories are
also visible from machines wiki and neptune.
There are 2 tape drives available on stego: a DAT and an Exabyte.
- DAT (standard density): /dev/dat
- EXABYTE (high density, no compression): /dev/exabyte
NOTE:
These two devices are symbolic links to the correct /dev/nrst? devices.
If you want to use exabyte compression or a version of a device that rewinds
after an operation, list the links (for example, ls -l /dev/exabyte)
and then check the man page for st for help on calculating device
numbers.
For ease in accessing the images from tapes, we recommend writing each 8K group of images as
a separate tar file. For example, the following command(s) writes
filename.num.0 through filename.num.7 to the Exabyte (DAT).
% tar cvf /dev/exabyte filename.num.?
% tar cvf /dev/dat filename.num.?
Two csh scripts are provided to spool images off to tape, with each group of eight written
as a single tar file. The scripts are wdat and wexa.
The csh script for wdat is shown below:
#!/bin/csh
# Usage: wdat startfile endfile rootname
set start=$1
set end=$2
set name=$3
set i = $start
setenv TAPE /dev/dat
while ( $i <= $end )
set num=`awk 'BEGIN {printf "%03d\n",'$i'}' </dev/null`
echo tar cv $name.${num}.?
tar cv $name.${num}.?
@ i++
end
To use this script, the observer types wdat followed by the starting and
ending file numbers followed by the root name (all the files must have the
same root name).
For example:
% wdat 003 035 ccd
will write all the files between ccd.003.? to ccd.035.? to the dat drive
with each group of eight as a separate tar file.
wexa works in the same manner.
- Biases
- Darks
- Flats
- CFH PF image distortion
- Some common shell commands such as ``cd'' and ``ls'' are also
implemented as mcdcom and mora commands.
- Be careful of ``rm'' however. In mcdcom it means
``read mosaic'' and in mora it means ``remove buffer n''.
- You can get to the the real ``rm'', or any other
shell command, by prefixing the command with the shell-escape
character. This is a `%' in mcdcom, and a `!'
in mora. Note that the current working directory may differ for
shell-escapes versus built-ins.
- Argument parsing at the mcdcom command line attempts to mimic
typical shell behavior as much as possible, but some subtle differences
should be expected. For example, trailing spaces after the final argument
may be taken to be part of the argument, even if it was not quoted.
- The observer should set the environment variable OBSERVER
manually before starting mcdcom (mosaic) in order to set the
OBSERVER FITS card for all images written by mcdcom.
- Two sym-links in the /dev directory (/dev/dat and /dev/exabyte)
have been set up for the recommended tape settings (no rewind on close,
no compression, high density exabyte, standard density DAT). Device
numbers for other combinations can be found in the manual page for ``st''.
- CFHT's Sparc 20, paniau, has been configured to look as much like
IFA's stego machine as possible. All of the necessary files to run the
``obs'' account live in /usr/uh8k/*, but sym links were created elsewhere
in the file system so things appear where they are needed.
- The hostname ``stego'' is an alias for paniau at CFHT.
- Two /etc directories exist on paniau, /etc.CFHT and /etc.UH.
The real /etc is just a sym-link to either one of these. (The /etc.*
directories cannot be in a path further removed from the root!)
In general the instrument works reliably. There are a few
places, however, where failures are more likely to occur. We identify the
know problem areas here:
Should insurmountable problems occur, or if there is ever any risk to
the instrument, please contact:
G. Luppino off: 808-956-6365
lab: 956-7515
home: 808-739-5686
email: ger@hokupa.ifa.hawaii.edu
Mark Metzger off: 808-956-8701
lab: 956-7515
home: 808-533-0741
email: metzger@tiro.ifa.hawaii.edu
Hubert Yamada off: 808-956-6648
lab: 956-7515
email: yamada@galileo.ifa.hawaii.edu