K2 tutorial for ESPaDOnS

Updated November 2021


Abstract -- This document presents the detailed Kealahou K2 tutorial for ESPaDOnS. Astronomers who were allocated CFHT time use the new CFHT Phase 2 system, Kealahou (Hawaiian for "the new way"), to enter the details of their observations. Within K2, help is available through "Help" buttons provided for each section; the "Help" buttons are linked to the various sections of this tutorial. Within K2, tool tips are also available by hovering over the "?" symbols shown throughout the page.

For any additional information, please contact the QSO Team by emailing qsoteam -=at=- cfht.hawaii.edu.

SUMMARY OF BASICS

Users should have by now consulted the general documents Queued Service Observing at CFHT - How QSO works at CFHT and General principles of Kealahou (K2). Reading those 2 documents should only take 15 minutes, so we recommend that users consult them at least once. A few highlights are repeated here:

ESPADONS & SNR MODE

QSO-SNR mode

In most cases, QSO-SNR is the default mode of operation. The SNR mode is not suitable if:

If you are unsure if the SNR mode is suitable or not for your program, please email the QSO team qsoteam -=at=- cfht.hawaii.edu

Details are available in the QSO-SNR document.

To use QSO-SNR in K2:

  1. Target: ensure you enter the V magnitude and Teff of your target; this allows the QSO team to verify exposure times.
  2. Observing Template: check the box "Use SNR", enter the goal SNR and the wavelength at which the SNR goal has been defined. The SNR goal is defined per single exposure, and per CCD bin (not spectral bin).
  3. Observing Template: you also need to enter the appropriate exposure time as returned by the ESPaDOnS Exposure Time Calculator

Tip for setting the SNR for cool stars (Teff < 3500K) with ESPaDOnS

When using the ESPaDOnS ETC on cool stars, the SNR may end up lower than expected because a cool star's SED differs significantly from that of a blackbody (what the ETC assumes). From 400 to 700nm, the predicted SNR is the one observed. From 700 to 1000nm, the measured SNR is much larger, twice as high at 900nm. If you set the SNR goal at <700nm, the observed SNR in the red will be higher than what the ETC predicts (which is fine unless saturation is a concern). If you set the SNR goal at >700nm, the flux levels in the blue will be very poor.

We recommend using our 730nm wavelength and adding a margin to the SNR goal, as much as necessary depending on the part of the spectrum of interest.

TABLE OF CONTENT:




ACCESSING K2 AND NAVIGATING WITHIN K2

Access to K2 is limited to users who have received telescope time in the QSO mode.

K2 is compatible with Chrome or Firefox; Microsoft Edge should also work. Safari is currently not supported. The system will not allow logins from incompatible browsers.

If you had a Phase 2 login in the old CFHT system, use the same username and password. If you had no previous account, you will be contacted to set up your password. If you have forgotten your password, please use the link "Forgot Password?". If you have trouble login in, please contact the QSO Team.

In K2, all the information for a program is found and entered on the same page.

Within a section, items are defined by using "Add new +"; you may edit a saved item by clicking on the pencil icon at the far right, and you may delete an item by using the trash icon also located at the far right. At the bottom of each section, you can control the number of items shown at the same time (the default is 10) without having to page through, and you may also move through pages of content.

When entering a new item, you can use the "Tab" key to move from one field to the next, or click on the desired field. The information entered in K2 is saved when the "Apply" button is clicked. Mandatory fields that have not been entered will be shown in red; the "Apply" button is greyed out until all mandatory fields have been provided. There is no submit button.

The Apply button is grey when some mandatory fields are missing.

Once items have been entered, you may search for specific ones in each section, by using "Quick Search". You may also sort items in any section by clicking on a column header.

The Quick Search functionality is available for targets, observing templates, observing groups, and exposures.

Within K2, help is available through "Help" buttons provided for each section; the "Help" buttons are linked to the various sections of this tutorial. Within K2, tool tips are also available by hovering over the "?" symbols shown throughout the page.

Help (this tutorial) and tool tips are available in K2.

Back to Table of Content




SUMMARY SECTION

In the Summary section, the Title, Abstract, PI name, and PI Email are those entered during Phase 1. The Release date indicates when the pixel data (the full FITS files) become public. By default, the metadata (e.g. name of the target and its coordinates) are publicly available immediately; an extension of the metadata proprietary period must be requested at the time of Phase 1.

The Allocated I-time was determined by your agency's Time Allocation Committee and might differ from the time requested initially during the Phase 1. Your program might also have been split between an A grade ("Must do") and a B grade ("Prioritized") program, or a B grade and a C grade ("Best effort"). Please fill in all programs that appear. Details about C grade programs are available here: www.cfht.hawaii.edu/en/science/QSO/C_programs.html. If your program is a Snapshot program, it will be used if sky conditions are not good enough for the Regular programs.

The Requested I-time is the sum of all the observations entered in K2; if the requested I-time is higher than the Allocated I-time, please ensure you have clearly indicated which observations should be carried out first, by selecting a High priority in the Observing Groups section.

The Observed I-time reflects the time spent on the sky to observe your program. Some of that time might not meet your requirements. The Validated I-time represents observations that have met your requirements, and were therefore validated; that I-time is charged to your program.

Additional I-time numbers reflect time spent repeating observations, or time saved by using the SNR mode. The Completeness indicates the progress made for your program.

You may enter additional information regarding your program by using the Program Comments field. Don't forget to use the Save Comments button!

Back to Table of Content




FIXED AND MOVING TARGETS

ESPaDOnS users may enter fixed targets (stars) or moving targets (e.g. asteroids).

FIXED TARGETS - For Fixed Targets, please enter the name of the object and use the Resolve Target button. If the name is found at CDS, this will return a proper catalog name (which may differ from the one entered), coordinates, and proper motion values. Equinox 2000.0 is assumed! If the values returned are correct, you may use "Link Target"; the coordinates and proper motion values will be automatically copied.

The target will also be indicated as being "PI linked" or "PI Confirmed". If the target name was not resolved at CDS, you may manually enter the necessary values by using "Custom Target". In this case, the target will be listed as "Custom Target" or have a Linked value of "No" (not linked to catalog values). If a target is indicated as being "System Linked", please use the Resolve Target button to link it to catalog values.

The V magnitude and Temperature are mandatory fields and are used to verify the exposure time and SNR goals entered. Provide a comment in the Summary if your stars are highly variable and/or this information is not reliable.

The Standard Star checkbox is optional, and is used to flag stars that are used for calibration, and have to be observed along with a scientific target.

Finding charts are mandatory, even for very bright targets. The "Select Finding Chart" button will automatically generate a finding chart with the proper orientation and scale (4 arcmin on a side). You may slide the chart so the cross is centered on your target, but please do not zoom in or out. If the chart generated is unclear or otherwise not useful, you may upload your own chart by clicking on "Select file"; please ensure that your own chart is about 4 arcmin, the image is in the optical, the file is a JPG and a crosshair clearly indicates your target. You may also edit the comment that is automatically generated; this is useful if the field is crowded or there is a companion nearby.

MOVING TARGETS - For a moving target, please provide a name and a V magnitude.

At least 3 sets of RA and Dec coordinate pairs must be entered, enough to cover the potential time of observation. The times are in UT.

If the moving target moves slowly and is to be observed with sidereal rates (with or without guiding), the set of coordinates closest to the observing time will be sent to the telescope.

If the moving target moves quickly enough that non-sidereal rates are requested, sets of coordinates (at least 3, up to five) will be picked and sent to the Telescope. The request will fail if there is not at least one time before and one time after the time of observation. If there are enough sets, the choice will be one before and four after the time the observation is selected. The sets must be spaced far enough apart in time to cover the longest OB they are used with. Current coordinates and rates will be interpolated by the Telescope Control System.

The "Select Ephemerides" button allows users to copy-paste a sample file that can then be edited and uploaded. Once the ephemerides file has been uploaded, K2 will show the first and last entries in the file (to check the completeness). The full file can be viewed by using "View Ephemerides".

For reference, here is the sample file provided in K2.

<?xml version = "1.0"?>
<!DOCTYPE ASTRO SYSTEM "http://vizier.u-strasbg.fr/xml/astrores.dtd">
<ASTRO ID="v0.8" xmlns:ASTRO="http://vizier.u-strasbg.fr/doc/astrores.htx">
<TABLE ID="Table">
<NAME>Ephemeris</NAME>
<title>Ephemeris for CFHT QSO</title>
<!-- Definition of each field -->
<FIELD name="DATE_UTC" datatype="A" width="19" format="YYYY-MM-DD hh:mm:ss">
<DESCRIPTION>UTC Date</DESCRIPTION>
</FIELD> 
<FIELD name="RA_J2000" datatype="A" width="11" unit="h" format="RAh:RAm:RAs">
<DESCRIPTION>Right ascension of target</DESCRIPTION>
</FIELD>
<FIELD name="DEC_J2000" datatype="A" width="11" unit="deg" format="DEd:DEm:DEs">
<DESCRIPTION>Declination of target</DESCRIPTION>
</FIELD>
<!-- Data table -->
<DATA><CSV headlines="4" colsep="|">
<![CDATA[
DATE_UTC           |RA_J2000   |DEC_J2000  |
YYYY-MM-DD hh:mm:ss|hh:mm:ss.ss|+dd:mm:ss.s|
1234567890123456789|12345678901|12345678901|
-------------------|-----------|-----------|
2021-04-26 04:30:00|02:43:51.70|-10:54:06.0|
2021-04-26 05:00:00|02:43:51.90|-10:53:50.0|
2021-04-26 05:30:00|02:43:52.20|-10:53:34.0|
2021-04-26 06:00:00|02:43:52.50|-10:53:18.0|
2021-04-26 06:30:00|02:43:52.70|-10:53:02.0|
2021-04-26 07:00:00|02:43:53.00|-10:52:46.0|
2021-04-26 07:30:00|02:43:53.30|-10:52:30.0|
2021-04-26 08:00:00|02:43:53.50|-10:52:14.0|
2021-04-26 08:30:00|02:43:53.80|-10:51:58.0|
]]></CSV></DATA>
</TABLE>
</ASTRO>

Back to Table of Content




OBSERVING TEMPLATES

Observing templates include information for the instrument's configuration (e.g. the use of the polarimetric mode and the exposure time) and the sky conditions or constraints that have to be met. The SNR goal also has to be indicated. One OT may be used later to create more than one Observing Group.

The OT name can have spaces and special characters but this is not recommended. Names are limited to 68 characters. The label is set by the system automatically.

Three observing modes are offered with ESPaDOnS: Polarimetry, Spectroscopy (Star only), Spectroscopy (Star+Sky). Choosing Polarimetry will automatically set observations with the required 4 exposures, each having the requested exposure time.

The current CCD can be used under three different readout modes: Fast, Normal and Slow. Each mode has its own readout time (charged), gain, and readout noise. Note that the overheads charged are more than the readout time; operational overheads to start and finish an exposure are necessarily larger than just the readout time. The table below presents the necessary information.

Readout Mode Noise Gain Overhead
Fast 4.7e 1.6e/ADU 20s
Normal 4.15e 1.3e/ADU 20s
Slow 2.9e 1.15e/ADU 33s

In polarimetric mode, three Stokes parameters are available for ESPaDOnS: Q and U (for linear polarisation), and V (for circular polarisation). Only one parameter can be selected per OT; if two or three parameters must be observed consecutively on a given target, this can be arranged at the OG level. In spectroscopy modes, only the I (intensity) parameter is available.

Sidereal guiding is used for Fixed Targets. Non-sidereal Tracking is selected for Moving Targets.

The number of sequences represents the number of times the exposures should be executed. For polarimetric observations, a value of 1 means that the 4 exposures will be taken once for the Stokes parameter specified. To take 3 exposures in spectroscopic mode, with the same exposure time, enter 3.

The SNR entered is per exposure (not per polarimetric sequence of 4 exposures), and for a CCD bin, or CCD pixel (not for the spectral bin). If you wish to reach SNR=100 after the 4 exposures from one polarimetric sequence, enter 50 (half the value). This SNR goal is used to check the exposure times and the quality of the observations.

The exposure time in seconds is for individual exposures. In Polarimetric mode, the maximum exposure time is 1800s minus the overheads. In the Spectroscopic modes, the maximum exposure time is 2400s minus the overheads. It is possible to take exposures shorter than 1.0 second (e.g. 0.6s). Once an OT has been saved (by using the "Apply" button), the ITime provided in the table includes all exposures, all sequences, and all the overheads.

Enter the Maximum Image Quality, airmass, and extinction acceptable, and the minimum distance from the Moon. The default values (1.5 arcsec seeing, 2.0 airmass, 1 magnitude of extinction, 5 degress from the Moon) are reasonable for many observations. Observations are typically carried under an Image Quality of 1 arcsec or better, regardless of the maximum IQ indicated. We often push the airmass to 2.5, and if this is acceptable, please increase the maximum airmass accordingly. Very bright targets can tolerate 1.5 arcsec, 3.0 airmass, and 1.0 magnitudes of extinction (or more). Very faint targets (Vmag of 12 or fainter) should be associated with an OT that has very little extinction (0.0-0.2 mag) and a greater distance from the Moon (30 degress or more).

Back to Table of Content




OBSERVING GROUPS

Standard OG - The simplest OG are of the Type "Standard" and are used to observe a target, once, without any time constraint. In addition to selecting the Type of OG, a Priority (High, Medium, Low has to be selected; the QSO Team first looks for High priority OG when planning observations. An OG can also be made Inactive if it is not to be observed; this can be useful if the configuration has to be confirmed, or if it is a placeholder for a later observation. After selecting a Target and and Observing Template, clicking on the Apply button will create and save the OG.

Monitor a Target - Targets that need to be observed more than once, with a regular period, are of the Type "Monitor a Target". When this Type is selected, a new subsection appear below. The Minimum number of required iterations is the minimum needed to provide a scientifically useful set of observations; the QSO Team will aim to obtain the full Number of Iterations (the higher number). The period for the observations is entered under the Time Interval, which can be specified in days, hours, minutes, or seconds. To observe a target every night, enter Time Interval = 1 day. To observe a target every other night, enter 2 days. If the periodicity is not very strict, it is possible to enter a value for the Tolerance before and the Tolerance after. If the Tolerance before is 2 days, the QSO Team may perform the observations 2 days before the time indicated by the value of the Time Interval. The optical checkbox Require Same Camera Run indicates if all the observations are to be taken within the same run, or if they can be spread out over 2 or more runs during the semester.

Observe in Phase - To observe an OG only once, but at a specific date from a list of periodic dates, select "Observe in Phase". This functionality is useful to perform one observation at the peak of a luminosity curve for a Cepheid, or at the time of the periastron for a binary star.

A start date/time and a period are entered to generate a list of calculated dates/times; the tolerance will be used to set the width of the time window. Each calculated date/time will be assigned that same time window. Periods will be in most cases entered in days or hours.

To view the list of calculated time windows, use the Edit button for the OG. The list of time windows will appear at the bottom of the details for that OG.

REELed OG - Two OG that must be observed in sequence, with a delay between the 2 OG, are described by using the REEL checkbox.

The OG which is being created is associated (linked) to a different OG that has to be observed first. Between the 2 OG, there can be a delay of days, hours, minutes, or seconds, with zero an allowed value; a REEL with a Delay of zero means that the 2 OG will be executed back to back. This feature is useful for observations that span more than 2 hours and therefore require the creation of 2 separate OG. If the delay between the 2 OG is not strict, it is possible to enter a value for the REEL window. If a REEL was created with a delay of 10 days with a 2 day window, the delay will be anywhere between 8 and 12 days.

Time Windows - To observe a target only during specific time windows, click the checkbox "Time Windows" and enter as many windows as needed for that OG. Note that the information entered is a time after which the OG has to start, and a time before which the OG has to start. The dates and times are entered in UTC, and a conversion in HST is provided below the input boxes.

Back to Table of Content




EXPOSURES

A log of exposures taken for the program will appear at the bottom of the page. A specific OG or target can be found by using the Quick Search functionality. Only validated OG (which have all of their exposures validated) are charged to the program.

The log includes the QSO Grade (from 1 to 5, with 1 given to the best exposures), and the QSO comments with additional information.

The "Distribution" button will open a new page with a Distribution Overview, Information on Downloading Files, the location of the raw and processed files, etc.

Back to Table of Content