Troubleshooting guide
C. Long Slit Alignment
1. Verify telescope pointing.
• Acquisition can be done with the Decker wheel in mos, MOS wheel in imaging, Filter wheel in H, and
Grism wheel in open1.
• Take a quick image (2-5 seconds) of an SAO or Fixed Bright Star near the target field, and make
certain the SAO star is well centered at the position of the slit or acquisition aperture for the slit mask
to be used. If is not, center the star with relative.offset.kpno.pl, then take another image. Once it is
well centered, Z the telescope (cf. § III.B. Nightly Startup Tasks: Startup on the sky).
2. Acquire target field.
3. Adjust focus.
• 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
arcseconds. Run fwscan on the stack of images to determine which focus setting was best (cf. § III.B.
Nightly Startup Tasks: Startup on the Sky).
• Alternatively, check the focus with imexam, key a or r and interactively focus the telescope.
• Record the telescope secondary temperature, for reference.
4. Acquire a guide star and begin guiding.
• In the Linux TV Guider GUI, Warp to Star.
• In the Linux TV Guider GUI, use the Guide pull down menu, and select Guide On (cf. Figures 6 & 8
in Guiding GUI's)
5. Take another image, and measure the target centroid. Use imexam, key a.
• Move the telescope so that the target is centered at the (x,y) coordinates of the long slit center or
the center of the acquisition box in the slit mask using guide.mos.offset.kp2m.pl.
• To quickly estimate the distance to move, draw a large ruler in ds9, and then double click on it to
get its pop-up GUI. Enter the (x,y) coordinates of the star, and the destination position along the slit.
Then click on the Distance pulldown menu, and select Arcseconds. The (x,y) distances correspond
directly to (East-West, North-South) motion.
6. For long slit, Move Decker wheel to the slit aperture using config.rel.mv.filter.grism.decker.wheels.pl. If
using a MOS mask slit, move the Decker wheel to the mos aperture if it is not already there.
7. Move MOS wheel to long slit or slit mask position. Use config.rel.mv.mos.wheel.pl.
8. Verify long slit is straight and still at the location measured earlier.
• Use imexam, as described in step 7, and measure across the slit with the j key at two different
positions. If dx is > 1 pixel, you should straighten the slit using tweak.mos.wheel.pl.
9. Take an image. One should be able to see the target within the acquisition aperture if using a slit mask or
within the slit if using a long slit
10.Use guide.mos.offset.kp2m.pl to center the star in the slit or acquisition aperture. Because one should be
very close to the correct position, the motions should be small.
• You may need to iterate this step, and peak up the flux from the object through the slit with additional
guided offsets; changing the ds9 display parameters, using zmax and log scalings may help.
• If using one of the NOAO slit masks, once the star is centered in the acquisition aperture, offset the
telescope 120 arcsec to the north or south using guide.mos.offset.kp2m.pl to center the star in one of
the slits. We recommend the lower (north) slit to avoid the noisy upper right detector quadrant.
D. Taking Spectra Once the Slit is Aligned
There are two options for taking data once the target is aligned onto the slit. The first option is to manually
perform the dither pattern, taking individual images after each guided offset. We sometimes do this for long slit
data of calibration stars, if we want to walk the star along the slit in a pattern other than an ABBA pattern.
Alternatively, one may use the standard ABBA dither script.
FLAMINGOS@2.1-m, Ver. 2.39, 2011 May 13 Page 27 of 46