Troubleshooting guide

Appendix 4: Additional Notes on MOS Plates
An example MOS plate for use at the 4-m is shown adjacent, in Figure 8, at
approximately full size (~105 mm in length).
The sizes of the slits and alignment boxes are usually the same size in pixels
for both the 2.1-m and 4-m telescopes.
The slitlets are 3 pixels (0.9" at the 4-m) wide, with a minimum length of
approximately 30 to 40 pixels (9" to 12" at the 4-m).
The alignment boxes are 25 to 30 pixels (7.5" to 9" at the 4-m) on a side.
Making one box 25” square will facilitate setup at the telescope.
We usually try to find guide stars with K magnitudes in the range 11–13.
Note that the position angle always points towards the HUB of the MOS
wheel and the masks are mounted into the MOS wheel with the orientation in
sky parity (E being ccw from N).
The view of the MOS wheel, from the side that will be seen when loading is presented on the next page. Copy
or download and print it (http://flamingos.astro.ufl.edu/Manuals/), and then annotate it as you load the plates.
Critical annotation items include (see Figure 8):
• Plate name or ID
• Rotator Position Angle for proper plate orientation on the sky
• Slit Width, in pixels
• Compass, with sky parity showing the orientation of North and East
After the wheel is back in the MOS dewar, and the dewar is on the pump, run the script
set.new.mos.plate.names.pl, so that the correct plate name is recorded in the FITS header when the plate is
selected.
FLAMINGOS@4-m, Ver. 2.39, 2013 April 23 Page 46 of 47
Figure 8: Example MOSplate.