PFIP User Observing Guide

• Check that the PFIP instrument control panel is running. If the control panel is not running, then it may be started by typing the following command in the pink ICS window:

  SYS> 4MSControl -panels PFIP &
  

  Select the tab labelled PFIP Observer in order to display the observer's GUI. This panel shows relevant info about the filter wheel, atmospheric dispersion corrector (ADC) and autoguider, and allows the user to change filters and update their associated focus offsets if necessary. A complete description of the control panel and the new UNIX software for the PFIP controller is available here.

  Please only use the PFIP Observer tab on the PFIP control panel, or the command line, when changing filters. If you change filters with the pull-down menu under the PFIP tab, then the filter focus offset will not be applied, since this is an engineering GUI.

• To bring up a telescope information window, type the following in the ICS pink window:

  SYS> tcsinfo &
  

• Check that the detector readout speed, binning and windowing are all as required for your run. The detector readout speed may be set to slow or fast using the following ICS commands:

  SYS> rspeed pfip slow
  SYS> rspeed pfip fast
  

  The following detector webpage lists the CCD characteristics for each readout speed. The detector binning may be set (for example to 2 by 2) using the following ICS command:

  SYS> bin pfip 2 2
  

  We recommend no windowing with PFIP. In this case, each of the two extensions could be displayed in a separate frame (ex from IRAF: "disp r1374405[1] 1" and "disp r1374405[2] 2") and will have two separate headers, and both CCDs of the mosaic could be displayed together using Frames / Tile control in the DS9.
  
  Alternatively, a single window may be defined that covers all (or some area) of both CCDs. In this case, a single extension FITS file will be produced that contains the relevant sections from each CCD. The following window will produce a 4308x4200 pixel single extension FITS file containing the full readout from both CCDs side by side:

  SYS> window pfip 1 "[1:4308,1:4200]"
  

  To disable the windowing, one should type
  
  SYS> window pfip 1 disable
  

  In both cases, the user should Invert X in the image display in order to match the normal sky orientation (N up, E left).
  
  For more information on windowing please see thefollowing link for general windowing commands.

• An IRAF session may be used to examine PFIP data. Check whether an IRAF session is already open on whticsdisplay1, and if not, then open a terminal and simply type:

  $> iraf
  

  This will open an xgterm with IRAF already loaded, and it will also open a DS9 image viewer. Change the current directory to the directory where the data is stored for the night (/obsdata/whta/YYYYMMDD where YYYYMMDD is the current date and whta may instead be whtb) and load the PFIP quick look package in IRAF by typing:

  ecl> pfip_ql
  

  Mosaic images may then be displayed by using the following IRAF command:

  pf> mosaicdisp <image>.fit
  

  Remember to set the correct DS9 image orientation in order to match PFIP images to normal sky orientation.

• Afternoon bias frames may be taken at any time, after ensuring that the dome lights have been switched off, using the following command(s) in the ICS pink window:

  SYS> bias pfip
  SYS> multbias pfip <nbias>
  

• Dark frames are not necessary for PFIP since there is no measurable dark current at -120 degC.

• To acquire dome flats, ask the TO (or duty engineer) to move the telescope to a blank part of the dome (elevation 45 deg). Switch off the dome lights and switch on the flat field lamps on the telescope control panel. Load the required filter in PFIP using either the PFIP Instrument Control Panel, or by issuing the following command in the ICS pink window:

  SYS> pfilter <name OR number>
  

  The command(s) to take dome flats may then be issued in the ICS pink window:

  SYS> flat pfip <exptime> "<name>"
  SYS> multflat pfip <nflat> <exptime> "<name>"
  

• Make sure that the automatic compensation of the telescope focus and autoguider focus for the different filter thicknesses are enabled, as well as the automatic update of the atmospheric dispersion corrector. The status of these corrections/updates may be determined from the observer's GUI where they will appear red if they are disabled. To enable them, select the tab labelled PFIP, and click to enable the Automatic Filter Focus Compensation, the AG Automatic Filter Focus Update, and the ADC Update as required. Alternatively, one may type the following commands:

  SYS> pfip_set -m filtfocus enable

  This enables the automatic compensation of the telescope focus for different filter thicknesses.

  SYS> pfip_set -m gdfoc enable

  This enables the automatic adjustment of the autoguider focus for different filter thicknesses.

  SYS> pfip_set -m adc enable

  This switches the atmospheric dispersion corrector on.

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• Ask the TO to send the telescope to a bright star (no brighter than magnitude ~10), or a not so crowded field of stars.

• All the broadband filters have an associated focus offset which is recorded by the support astronomer in the ING filter database. During the focusing procedure we determine the zero point telescope focus zp (mm) as defined in the formula below, which is independent of the filter used:

  Telescope Focus (mm) = zp + DF + TC

  where DF (mm) is the filter focus offset (which depends on the filter thickness) and TC (mm) is the focus temperature correction. Therefore select any one of the broadband filters available in the filter wheel with a known focus offset.

• Execute a focus run using the following command in the ICS pink window:

  SYS> quickfocusrun pfip &

  A GUI will appear in which you should enter appropriate values for the starting telescope focus (e.g: 85.30mm), the focus step (e.g: 0.05mm), the number of focus steps (e.g: 9), the exposure time (e.g: minimum 10 seconds to average out seeing effects), and the telescope offset between focus steps (e.g: 15"). Click the Run button on the GUI and a script will run to take multiple exposures on one image, offsetting both the telescope focus and telescope position between exposures The telescope movement between the first two exposures is twice the requested length. On the resulting image, each star will be imaged multiple times, forming a "trail" down the image.

• To find the best telescope focus value, use the IRAF pfip_ql task pfip_qstarfocus as follows:

  pf> pfip_qstarfocus r??????.fit fstart=<focus start value> fstep=<focus step> pstep=<telescope offset> nexp=<no. of focus steps>

  Mark the first star in each star sequence with an "m" for a set of unsaturated stars uniformly distributed across the displayed CCD image, and then press "q" to quit. Wait until an xgterm appears showing the FWHM (in arcsec) and ellipticity plotted versus the telescope focus value. A star can be deleted from this plot by typing "d" over the star in the displayed image, and then typing "q" to estimate the best focus value again. The task pfip_qstarfocus reports the best telescope focus value and the best achieved FWHM (in arcsec) both in the IRAF session and in the plot title.

• Set the telescope focus value to the best value determined above using:

  SYS> focus <focus value>

  This step must not be skipped because the quickfocusrun command leaves the telescope focus set to the last value of the focus sequence.

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• To take a science exposure, issue:

  SYS> run pfip <exptime> "<name>"

• To take multiple science exposures, issue:

  SYS> multrun pfip <nrun> <exptime> "<name>"

• To take a bias image, issue:

  SYS> bias pfip

• To take multiple bias images, issue:

  SYS> multbias pfip <nrun>

• To take a dome/sky flat field image, issue either of:

  SYS> flat pfip <exptime> "<name>"
  SYS> sky pfip <exptime> "<name>"

• To take multiple dome/sky flat field images, issue either of:

  SYS> multflat pfip <nflat> <exptime> "<name>"
  SYS> multsky pfip <nsky> <exptime> "<name>"

• To take a test image that is not recorded in the night log, issue:

  SYS> glance pfip <exptime>

• To abort a current exposure and not readout the CCD mosaic, issue:

  SYS> abort pfip

  You may have to issue a ctrlZ and then "SYS> bg" to put the current exposure in the background first.

• To finish a current exposure and readout the CCD mosaic, issue:

  SYS> finish pfip

  Again, you may have to issue a ctrlZ and then "SYS> bg" to put the current exposure in the background first.

• To adjust the exposure time of an already started exposure, issue:

  SYS> newtime pfip <exptime>

  Again, you may have to issue a ctrlZ and then "SYS> bg" to put the current exposure in the background first.

• To set the telescope focus to some value, issue:

  SYS> focus <focus value>

• To offset the telescope in RA and Dec from the origin, issue:

  SYS> offset arc <RA offset in "> <Dec offset in ">

  Note that these offsets are absolute, and hence repeating the same offset command has no effect on the telescope position.

• To define an aperture offset, one may use the following two commands, issued in order:

  SYS> user "enter aperture <number> <x offset in "> <y offset in ">"
  SYS> user "ap 0"

  The offsets are in instrument coordinates and the sign criteria are described here. To set the aperture to the centre of CCD1, issue:

  SYS> user "enter aperture 0 250 0"
  SYS> user "ap 0"

• To go to an object in the TCS catalogue, issue:

  SYS> gocat <object name>

  However, it is a probably better to let the TO do this for you, since he/she is responsible for the telescope itself.

• To offset the telescope in x, y and/or position angle, while keeping the autoguiding loop closed, issue:

  SYS> user "tweak <x offset in "> <y offset in "> <PA offset in deg>"

  The size of these offsets is limited by the autoguider probe field of view of ~12"x12".

4.3 Mechanism Commands

To change the current PFIP filter using the command line, issue:

SYS> pfilter <number or name>

It is not recommended to use this command within scripts. The following command can be used instead:

SYS> pfip_move -m filter <number or name>

For the autoguider, one can change the current filter by issuing:

SYS> pfip_move -m autofilt <number or name>

4.4 Quick Look Package

An IRAF package pfip_ql is available to help support astronomers to carry out the PFIP setup on the first night after an instrument change. Observers can also use some tasks from the package to display and analyse the data.

To use the IRAF PFIP quick look package pfip_ql, open an IRAF session and load the package as described under "Afternoon Preliminaries". The useful tasks in this package are as follows:

• To display each CCD of a PFIP image in a separate frame within DS9, issue:

  pf> mosaicdisp <image>.fit

  Remember to tile the frames to see both CCD images.

• To determine the best telescope focus from an image taken with the observing system command quickfocusrun, issue:

  pf> pfip_qstarfocus <image>.fit fstart=<focus start value> fstep=<focus step> pstep=<telescope offset> nexp=<no. of focus steps>

  See the instructions on "Focusing The Telescope" for details on how to select appropriate focus stars.

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6.1 Field orientation for rotator PA=0

6.2 Field shift after applying an aperture

                N
      +--------++--------+  sky PA = 0
      |        ||  x     |
      |        ||<-----* |
      |        ||      | |
      |        ||      | |
      |        ||     y| | E
      |        ||      V |
      |        ||	 |
      |        ||	 |
      |        ||	 |
      +--------++--------+

6.3 Minimum recommended exposure time

6.4 Readout time function of speed, windowing and binning

PFIP Mosaic Mean Readout Times
Readout Speed	X Y Binning	Windowing	Readout Time (s)
Slow	1 1	None	38.3
Slow	2 2	None	12.3
Slow	1 1	[900:1100,1:4200]	23.2
Slow	2 2	[900:1100,1:4200]	11.7
Slow	1 1	[1:2148,1900:2100]	3.1
Slow	2 2	[1:2148,1900:2100]	1.8
Slow	1 1	[900:1100,1900:2100]	2.3
Slow	2 2	[900:1100,1900:2100]	3.0
Fast	1 1	None	30.0
Fast	2 2	None	9.8
Fast	1 1	[900:1100,1:4200]	22.4
Fast	2 2	[900:1100,1:4200]	11.3
Fast	1 1	[1:2148,1900:2100]	2.7
Fast	2 2	[1:2148,1900:2100]	1.6
Fast	1 1	[900:1100,1900:2100]	2.3
Fast	2 2	[900:1100,1900:2100]	1.6

6.5 Defocus due to mosaic non-coplanarity

6.6 Fringing

6.7 DS9 Image Orientation