Troubleshooting guide

• If targets are faint, you may need to offset a small amount (20") and work with a scaled difference
image. See the comments at the end of this section on how best to do this. Integration times may need
to be increased, too.
6. Have the telescope operator adjust focus on the TV camera,
• The guide camera should be confocal with FLAMINGOS, and should give a good starting focus.
• Next, take a series of images with FLAMINGOS over a range that covers best focus, offsetting the
telescope between each image; use relative.offset.kpno.pl and dither back and forth by 10 – 20". Run
fwscan on the stack of images to determine which focus setting was best (cf. § III. B. Nightly Startup
Tasks: Startup on the Sky).
• Record the middle dome temperature.
7. Have the telescope operator acquire a guide star and start guiding.
• Verify that the guide probe radius is greater than 100 mm, in order to avoid vignetting.
8. Set the Decker wheel to the mos baffle using config.rel.mv.filter.grism.decker.wheels.pl.
9. Verify the decker is straight (check the edge of the decker MOS baffle); use tweak.decker.pl if necessary
(cf. the previous section on long slit alignment).
10.Measure the star centroids and write them to a stars file for xbox:
• imexam logf=stars keep+
• Type a on each star
11.Insert MOS plate using config.rel.mv.mos.wheel.pl.
12.Check the plate is straight on the array with by stretching the display to see the plate frames. If it looks
significantly tilted, use a ds9 ruler to estimate the offset angle and adjust it with use tweak.mos.pl (cf. the
previous section on long slit alignment).
13.Measure the box centers and write them to a box file for xbox. Measure the boxes in the same order as
you measured the stars.
• imexam logf=box1 keep+
• type e to generate a contour map
• type g to get the graphics cursor
• center the cursor on the box and type x
• type i to return the image, and repeat this process for the other boxes.
• If you cannot see the box well in the contour plot, consider starting over after setting the upper contour
limit threshold to ~5,000 ADU; use epar eimexam and change the upper limit from the default value
of indef.
14.Run xbox:
• Type epar xbox
• Set the parameter image to the most recent mask image
• Set the parameter input = box1(the log filename you used in imexam)
• Set the parameter stars = stars (the log filenames you used in imexam)
• Type :go
• An xgterm window with two cross-cut plots through the box, one each for the x and y axes will pop
up.
• Type q to step through each of the boxes in the graphics window. If the box center is not clearly
detected, use the f key to force the center, and g to force the signal threshold.
• After the last box it will pop up a window showing graphically how much each box must move to
acquire the alignment target. Type q again.
• xbox finally will print out how much to rotate the MOS wheel (in degrees) and offset the telescope (in
arcseconds). When xbox is configured for the present 4-m setup, the offsets printed out should
directly correspond to the offsets to type to offset the telescope (see above).
• Use relative.offset.pl δRA δDec to offset the telescope.
• Use tweak.mos.pl to rotate the MOS wheel by the amount suggested.
• Translational offsets > 0.5 pixel ~ 0.2" and rotational offsets > 0.01° should be performed.
15.Take another image. At this point you should have stars in boxes. See the following notes on what to do
if the alignment targets are so faint as to require long integrations and background subtraction.
FLAMINGOS@4-m, Ver. 2.39, 2013 April 23 Page 29 of 47