Troubleshooting guide

MOS plate data.
Walking up the slit:
We usually move up the slit in steps of 10" for a total of 5-7 positions.
Use singleimage.pl to take an image by hand at every location.
Use relative.offset.kpno.pl to move the star up and down the slit (while continuing to guide).
Setup to execute a dithered ABBA script:
1. Zero the telescope offsets; type clear.offsets.kpno.pl and type y at the prompt.
2. Insert filter and grism combination with config.filter.grism.decker.wheels.pl.
3. Verify bias is set to 0.75 V for spectroscopy when prompted after moving the grism wheel.
4. Configure filename and exposure time.
For all spectroscopic observations we now recommend taking quartz or dome flats only after the target
observations (cf. Step 8). More details may be found in the next section on calibrations.
5. Take a single junk frame. Set the exposure time to the same exposure time you want to use on your
object. You should do this because the first image taken in low-flux conditions after being in high-flux
conditions has lower counts than normal. For example, the alignment or calibrations might be taken at 30
seconds and the object taken at 300 seconds, so you need to take a junk image at 300 seconds before
taking any real data.
6. Configure the spectral dither sequence using config.mos.dither.kp4m.pl.
Make certain the PA is correct.
Set M_RPTPAT to the number of times to repeat the pattern.
Set M_THROW, the distance in arcseconds between the A & B beams (which are symmetrically offset
about the telescope zero point). For MOS observations we use 4 arcseconds.
If USEMNUDG = 1, the ABBA pattern will be offset along the slit by M_NDGSZ (in arcseconds) on
pattern repeats. For MOS observations we use M_NDGSZ = 0.3. Alternatively, one can execute the
dither sequence with one ABBA pattern at a time, and use relative.offset.kpno.pl and
clear.offsets.kpno.pl before repeating the ABBA pattern. Just keep track of the size and number
of offsets.
7. Start spectral dither sequence, dither.mos.kp4m.pl. Repeat as necessary.
8. Take one or more sets of quartz or dome flats at end of spectral dither sequence (cf. § V. Taking Spectra
with FLAMINGOS: E. Taking Flats and Wavelength Calibrations).
9. Take a long slit spectrum of a telluric absorption star at an airmass at the middle of the dither sequence.
Use a bright star with spectral type G5-6 V.
10.Some observers also take a long slit spectrum of an A0 V star.
E. Taking Flats & Wavelength Calibrations
There are two types of calibrations required for long slit and MOS spectra: wavelength calibration and flat
fields. The 4-m guider/rotator above FLAMINGOS provides a set of quartz and arc lamps for these calibrations.
NOTE: The 4-m calibration projection unit was designed for the RC spectrograph, whose field is smaller than
10 arcmin. Therefore, this does not provide uniform coverage of the entire FLAMINGOS field of view, and
flats/arcs will be significantly weaker at the ends of the mask or slit. In addition, the quartz optics within the
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