PFIP (PRIME FOCUS IMAGING CAMERA) is an optical mosaic camera for use at the prime focus of the 4.2 WHT. Prime focus imaging at the 4.2 WHT is available using 2 EEV 2kx4k CCDs, giving a pixel scale of 0.24" and a field of view 16.2'x16.2' (with a gap between the two chips of 9").

PRIME is an instrument placed in the secundary mirror.

• USER> STATION PRIME
• USER> INSTRUMENT PFCCD
• USER> AGSELECT PRIME
• Zeroset AZ and ALT

• USER> AZ 298
• USER> ALT 89
• USER> ENG
• USER> ZERO AZ TAR
• USER> ZERO ALT TAR

Drive AZ and ALT slowly in + direction over the zeroset target points, then switch to computer control again

• USER> ZERO AZ ABS
• USER> ZERO ALT ABS

• USER> ZERO ROT ABS
• USER> WAVELENGTH 0.6
• USER> TEMP ...
• USER> PRESS ...
• USER> HUMI ...
• USER> UT1UTC ...
• USER> CAL LAST
• USER> FOCUS 86.55 (13/05/2005)

Autoguider:
The light to the autoguider is fed by a fiber, giving a FOV (25"x25"). Use in twilight to define the AG window.

Use the standard uDAS autoguider from leo (whtdas3) with 'obssys 1', 'startobssys' and 'startag AG1' followed by 'option 3'.
DS9 display tool will also appear as well as the TV Guider Control. This box allows you to change exposure times, take fields and set the TV and Guider going. Images are piped directly to the display tool.

- GSS is used for finding guide stars, connect to LPVS3 via LAT and login as GSS. Select WHT and instrument PRI.

From the Observer interface the Autoguider probe can be moved, the control GUI starts using the command from the SYS prompt.

SYS> 4MSControl.

The main use for this GUI is to change the filter in the science camera. Click on the tab "PFIP Observer" (opens by default) and underneath the button "Update filter list" there is a menu-bar with which you choose the filter. Next press the button with the wheel to actuate the move to the selected filter. A complete list and description of the PFIP mechanisms commands and new PFIP controller solaris software (PFIP GUI included) can be found here.

The ORIENTATION of the movements of PRIME respect the sky:

The CCD gap is about 39 pixels.

                                SKY PA=0        DETECTOR

X,Y axis shows direction star moves for a positive offset or aperture

PGDY----> width 1500 units =25"

PGDX----> width 1500 units =25"

Filling the cryostat, the cryostat is prime, so it is necesary to park the telescope at AP2.

From the TCS;

---->ROT MOUNT -75 (FILLER TUBE AT TOP)

---->AZ:300, EL:15. pass to ENG. mode, go to local and move to AP2.

After filling move the telescope from local to AP1. Press ZN and when the telescope pass from AP1 (sound) press AP1, the telescope stop in a position >11.

SWITCH TO COMPUTER MODE.

Rotator centre:
Without any aperture offset, the rotator center was determined in October 2002 at a point on CCD1 at x=2085, y=2028 +/- 3 pixels, very close to the gap between the two CCD's. Note that the imaging area on each chip extends from x = 53 to x = 2100. Below x=53 is the overscan region, this is electronically generated and no physical pixels correspond to this region.

Calibrate procedure:
As the rotator center is close to the gap between the two chips, calibrate is best done with a modified aperture 0 offset. Make sure to restore the original value after calibrate!

---->USER> enter ap 0 250 0 (rotator center will be close to center of CCD1)
---->USER> cal faint, then ^Z (go to the next faint calibrate star)
---->USER> rot sky 0
when in position take a short exposure and measure x and y within the defined window, reading out the center of chip 1.
---->USER> rot sky 180
when in position take a short exposure and measure x and y, then calculate the rotator center. This should be close to the center of chip 1.
---->USER> cal faint
take short exposures for all 7 stars, calculate offsets (in RaDec) with respect to the rotator center and input these in HANDSET mode.

Determine aperture offset:
In order to move the rotator center to the center (gap) between the two chips, aperture 0 had to be defined as -11.3 -6.7 (October 2002). If you need to define aperture 0, so the rotator center falls on the center of chip 1 or 2, you need to add +/- 250", (1024pixels+19.5pixels)*0.24"/pixel, this is half the size in x plus half the width of the gap:

CCD1: +250 0
CCD2: -250 0

Acquisition:

PFIP usually observes with a Rot Sky 0, so it is important to be sure that the rotator doesn`t reach the limit switch.
If requested to center the object on either of the CCD's instead of the center (gap) between the two chips, change aperture 0 by adding +/- 250" in x or define an additional aperture.
The MOUNT PA range is only 357 degree total, (limits: -163.37,193.63) hitting the limit you can't simply unwrap, you have to wait a certain time until you got past the 3 'forbidden' degrees, this may take a while, depending were the object is on the sky; therefore watch carefully what the limits are, each time you move to a new source!

Guiding:

Open a terminal, logon as whtobs and type 'obssys' followed by the correct option. From this TO-window the probe is moved with command 'agprobe' and the guider focus with 'agfocus'. Focus was around 11000 (May 2004). 'pfip_status' lists the status.

GSS search results require little or no correction, even when an APERTURE OFFSET is included. GSS was 100% correct at ROT SKY 0 including apertures. Other angles than ROT SKY 0 have not been tested, but there is a good chance that GSS will also work there.

Dithering while keeping the guide star:

The observer will usually use the OFFSET ARC command to make a dither pattern. Even a dither of 10 arcsec will require adjusting the guide probe position because the star image is so large compared with the Guider field (unless you are clever enough to place the star in the correct corner and make a 4-point square dither pattern). Basically for every 10 arcsec offset, you need to move the probe 600 units. A telescope offset in +X will require a probe offset in +X, but a Y offset requires the probe to be offset in the opposite Y direction to recapture the star.

• The data are recorder in the obs system. Use the fitsinit/fitout or tar

-------- © 2005 Isaac Newton Group of Telescopes --------
Last Updated: 23 May 2005 Juan Carlos Guerra jcg@ing.iac.es