CAT User's Guide
FAT-CAT
The Field Acquisition Telescope for the Coude Auxiliary Telescope,
FAT-CAT, is a wide field CCD camera mounted at the top of the focusing
mechanism for the CAT secondary mirror and is used as a finder for the
CAT. In its current configuration it consists of an Opticstar DS-335C
CCD camera coupled to a 180 mm f/2.8 Nikkor lens with a plate scale of
3.95 arcsec/pixel and an effective field of view of 135 arcmin x 101
arcmin. The camera is connected to a computer named fatcatpc that
resides on a shelf near the MOS via a USB cable. The camera software
is run remotely using a VNC environment. To use FAT-CAT follow these
instructions:
- Open an xterm on catpc and type vncviewer fatcatpc (use the
standard VNC password)
- Click the start button within MS-Windows XP on fatcatpc and
select the program Nebulosity
- Click the maximize button in the upper right corner of the
Nebulosity program
- Click the camera button and select Opticstar DS-335C from the
pull-down menu
- Click the advanced button and check the box for 2x2 binning
- Set the exposure time to a value between 3s and 18s
- Set the number of exposures to 1
- To take an image without saving it click the preview button
- To take an image and save it type a name for the image and
click the capture button
At the start of the night center a star on the slit and start guiding
then capture an image making a note of the (row,column) coordinates of
the star. Move the cursor to the location of the star on the image and
right click the mouse to mark this position. To use FAT-CAT to find
your way when you are lost follow these instructions:
- Acquire an image as per the instructions above
- Mark the position of the target star (using a finder chart as
a guide)
- Using the compass on the CAT guider image as a guide mark a
third point on the image such that the three points form a right
triangle with the adjacent sides parallel to the compass directions.
- Select the measure distance option from the image menu and
enter the plate scale (7.91 arcsec/pixel) and the program will compute
the lengths of the 3 sides of the triangle formed by the three points
you previously selected. Referring again to the CAT guider compass you
can now compute the offsets in RA and DEC that will put the target
close to the slit of the spectrograph. If the target star is still not
visible on the CAT guider take another exposure and repeat the above
steps. (You may have got the signs of the offsets wrong!)
Known USB issues: When you first start up the Nebulosity program and
select the camera if you are greeted with a popup window saying
"Cannot Init Camera" then close the program and go upstairs and unplug
the USB cable coming from the camera from the USB extension cable and
then reconnect the two cables. Do not unplug the USB cable from the
computer!
If you have any other questions or need further instructions please
contact Thomas Lowe at lowe@ucolick.org