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The PFIP users guide

Preliminaries
Starting the system

Starting up the observing system
Starting up the instrument control system (ICL)

Focusing
PFIP observing commands

PFIP data acquisition commands
PFIP mechanisms commands

Shutting down the system
Writing data tapes
Useful notes

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1. Preliminaries

Observing with PFIP involves the use of two computers:

taurus, a Sun workstation from which we control the observing system
and the ICL computer, which controls the instrument (all the mechanisms)

2. Starting the system

2.1 Starting up the observing system

Log on to the Sun workstation taurus
- LOGIN: whtobs
  PASSWORD: provided by your support astronomer
An openwindows session starts, and an xterm pink window (labeled "Central intelligence of observing system") and several xterm orange windows will appear. Also a netscape window appears, which shows the UltraDas Software Operations Manual (command dictionary included).
Minimize all the orange windows except the one corresponding to the DAS (data acquisition system) computer which controls PFIP (get its name from the white board above the ICL computer). It is entitled DAS5 at the moment (Nov 02).
Start the data acquisition system:
- Type obssys in the DAS (orange) window. It defines the software to use and will then prompt you to select the observing system. Type the option number corresponding to PFIP (option 18 at the moment (8/4/02)) and wait until the prompt DAS> appears.
- Type DAS>startobssys to start the software. Wait until the prompt is back and minimize this window (it is not needed until you shut down the system).
Start the system computer:
- Type obssys in the pink window.
- Enter the same option number as in the orange DAS window and wait to get the prompt SYS>.
- Type SYS>startobssys
  This initializes the telescope control software (TCS) link, the EEV mosaic SDSU controller, and brings up several new windows:
  - An "identify" window.
    Enter your name and proposal identification.
  - The observing log.
    The log is automatically updated each time a new file is written to disk. To put comments on a line click once with the mouse on the line and a box appears where you can type shorts comments.
  - The detector info display window
  - The "talker" window. It displays messages from the observing system to the user.
If you want, you can bring up a telescope info display window. Type:
SYS>tcsinfo&
Set the detector readout speed to slow or fast (as desired) by typing for example:
SYS>rspeed slow
Have a look at the EEV mosaic's page for details on the operational characteristics for each readout speed.
To examine PFIP data:
- Type: cl>pfip_ql in IRAF, to start up the PFIP quick look package.

2.2 Starting the instrument control system (ICL)

The ICL is started in the afternoon prior to your run by the operations team. The ICL monitor should have two windows: one showing the light path of PFIP and another with the prompt hh:mm:ss> (local time) for command typing.
If this is not the case, call the duty engineer.

Then, on the ICL interface type:

hh:mm:ss>psetfoc enable

hh:mm:ss>psetgdfoc enable
Enables the automatic adjustment of the autoguider focus for different filter thicknesses

hh:mm:ss>adc_auto enable
Switches on the automatic updating of the atmospheric dispersion corrector

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3. Focusing

The best telescope focus value for observing with PFIP is ~86.2mm (October 2002), but this value can change slightly each time the camera is put in the telescope.

Select a star (no brighter than magnitude ~10) or field of stars but not too crowded, and tell the telescope operator (TO) to slew the telescope to it.

Select a filter. All the broadband filters have an associated focus offset which is introduced by the support astronomer in the ICL PFIP filter database.
During the focusing procedure we determine the zero point telescope focus (z.p.) as defined in the formula below, which is independent on the filter used, therefore select any of the broadband filters available in the filter wheel.
real telescope focus= z.p. + offset(f) + compensation (T)
where:
o offset(f)=focus offset which depends on the filter thickness
o compensation (T)=automatic compensation applied to the telescope when temperature changes.
Take exposures for different values of the telescope focus using the command SYS>quickfocusrun&.
A dialog box will appear and you must fill in the appropriated values (e.g. starting telescope focus 86.00mm, step 0.05, number of steps 9, exposure time 12s). The script will take the exposures, offset the telescope between them and store the exposures on the same frame. The offset between the first two exposures is double.
Find the best telescope focus value: on lpss13, in the iraf session and within the PFIP quick look package type:
pf>pfip_qstarfocus rxxxxxxx.fit
IMPORTANT: Set the telescope focus value to the best value determined above; on the ICL interface type: e.g.:
since the telescope focus is left to the last value of the sequence after running quickfocusrun.

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4. PFIP observing commands

A complete list and description of the commands can be found in the command dictionary of the UltraDas Software manual. A summary of the most commonly used commands is given here for a quick reference:

PFIP data acquisition commands
Some of the most important commands related to data acquisition are listed below (arguments are denoted by <>):
- run <int time> <"title">
  Takes a run and saves it in: rxxxxxx.fit.
  E.g. run 600 "N157 B", takes a 600s exposure and store it in the output file (e.g. r240976.fit). The title of the fits file is set to "N157 B".
- flat <int time> <"title">
  Takes a run and set the OBSTYPE header parameter to FLAT.
- bias <int time> <"title">
  Takes a run and set the OBSTYPE header parameter to BIAS.
- glance <int time>
  Takes an exposure and saves it in s1.fit. This file is overwritten when a new glance is taken.
- scratch <k> < int time> <"title">
  Takes a run and saves it in: sk.fit.k is an integer within the range 1-99. The scratch file sk.fit is overwritten when a new scratch<k> is taken.
- multrun <m> <int time> <"title">
  Same as run but repeats the run sequence m times and generates m output files.
- multflat <m> <int time> <"title">
  Same as flat but repeats the run sequence m times and generates m output files.
- multbias <m> <int time> <"title">
  Same as run but repeats the bias sequence m times and generates m output files.
- abort
  Abort an exposure. The data is not saved to disk
- finish
  Terminates an exposure and save the data to disk.
- newtime <int time>
  Change the length of an exposure (e.g. newtime 900)
The arguments above stand for
< int time> Integration time in seconds.
< "title"> Title of the exposure recorded in the image header (optional argument).
PFIP mechanisms commands

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5. Shutting down the system

Shut down the system computer:
Type SYS>shutdownobssys in the pink window and wait until the prompt is back. Most of the windows will disappear (log, detector info window, talker, identify window).
Shut down the DAS:
Type DAS>shutdownobssys
on the DAS orange window corresponding to PFIP and wait until the prompt is back.
Close the TCS display window manually: from the File menu, select Exit
Log out of PFIP's control computer: click the right mouse button on the background screen and select exit.

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6. Writing data tapes

Get a DAT tape from your support astronomer or TO,
Put the DAT tape in the DAT drive in lupus (in the terminal area).
Open up an xgterm.
cd /obsdata/wht?/yyyymmdd
There are two options:
- Use the tar command to write the data tape; e.g.:
- or alternatively type:

NOTE: If you write the data tape with fitsinit/fitsout, use the mscrfits command in the mscred IRAF package for reading the data. This is necessary because PFIP images are multi extension images.

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7. Useful notes

The orientation in the PFIP images is North up, East right when the rotator position angle is 0 degrees. For sky PA=90deg, North is left and East is up

The scheme below shows how stars move when applying a positive offset or aperture with sky PA=0 (e.g. aperture 0 -20 -10, moves the star 20" E and 10" N, i.e. right and up). N +--------++--------+ sky pa=0 | || x | | ||<-----* | | || | | | || | | | || y| | E | || V | | || | | || | | || | +--------++--------+

Try to avoid exposures where the direction of the azimuth axis reverses (i.e. when the parallactic angle is 90 or 270 deg). When there is a reverse in azimuth during tracking or guiding, the prime focus rotator jumps by ~400". If autoguiding is on, the autoguider will put the guide star back into position on the autoguider chip, but the jump in rotation will cause a movement of up to ~3.3" on the detector. Stars will then appear double or elongated.

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Last Updated: 13 November 2002
Almudena Zurita, azurita@ing.iac.es