Troubleshooting guide

V.Taking Spectra with FLAMINGOS
A. Overview
FLAMINGOS may be used for obtaining long slit or multi-object slit spectra; please see Section I.
FLAMINGOS + KPNO 4-m Overview for resolving powers within selected passbands. As with imaging, the sky
emission is variable and bright. It is necessary to subtract this contribution from the target spectrum. To this
end, observers generally dither the target up and down the slit. Two modes that we use include walking up the
slit at 5 to 7 different locations, and nodding the telescope back and forth between two offset positions, or
beams, A and B, in an ABBA pattern, symmetrically placed about the target's initial alignment position. Dithering
in an ABBA pattern can be done by hand, or automatically with a script. Walking up or down the slit must be
done by hand.
Telescope guiding is required, as the integration times are generally long, and the time to align a long slit or
MOS plate is also significant. The South Port guide probe (x, y) location is shown on the TCS Video unit.
The radius, r = √(x
2
+ y
2
), from the center of the field of view must be ≥100 mm or else the guide probe will
vignette the FLAMINGOS field.
The default bias for spectroscopy is 0.75 V, where the array has lower dark current than at the imaging bias of
1.0 V. The present bias value may be obtained by hitting the Update All Items button on the UFSTATUS
GUI. N.B.: the MCE4 array controller automatically set the bias to 0.776 V on boot, which is not a bias
voltage used in any configuration. The initialization script initflam.pl sets the bias to 1.0 V, and then
queries whether you wish to change the bias. If MCE4 crashes and you have to run initflam.pl, don't forget
to reset the bias for spectroscopy!
The general outline for spectral observations is as follows:
1. Set Instrument Position Angle (PA) to match the slit PA.
2. Verify telescope pointing on a SAO or Fixed Bright star close to target position.
3. Acquire target close to the center of the FLAMINGOS field of view (FOV).
4. Check focus.
5. Acquire a guide star and start guiding.
6. Insert appropriate decker baffle (long slit or MOS) and check its alignment.
7. Insert and align long slit or MOS plate.
8. Insert desired filter and grism.
9. Set bias to 0.75 V for spectroscopy.
10.We recommend that one take quartz or dome flats after the target observations to avoid loss of guiding
which can occur if flats are taken prior to the target observations.
11.Take a junk spectrum.
12.Configure spectral dither pattern parameters.
13.Execute spectral dither pattern.
14.Take all of the required quartz or dome flats, and HeNeAr wavelength calibration data if desired.
15.Repeat steps 1 – 14 with the long slit on a bright telluric standard star (G5-6 V) close by on the sky.
6
16.You may want to take a long slit spectrum of an A0 star at low airmass as well.
17.Take darks (~20 each) at every exposure time that was used for flats, wavelength calibrations, science
target spectroscopy, and standard star spectroscopy. Be sure to use the spectroscopy bias of 0.75 V.
6 If you intend to use the 3-pixel MOSplate long slit, you can leave the decker positioned at the MOS baffle.
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