Troubleshooting guide

IV.Imaging with FLAMINGOS
A. Overview
FLAMINGOS may be used for imaging through J-, H-, K-, and K
s
-band filters. Sky emission in these bands is
variable and may be bright
3
. Exposure times are kept reasonably short as a result and guiding is not required.
The general observing procedure is to point the telescope in a dither pattern about the source. FLAMINGOS
has a dither script with several different dither patterns available. They all are oriented in a square grid in (RA,
Dec); the ordering through the pattern is executed in the same psuedo-random order every time (it is not a
raster).
For deep imaging exposure times up to 120 seconds in the J-band, and up to 30 – 90 seconds in the H- and K-
bands are common. The shortest possible exposure time used with FLAMINGOS for scripted observing is 2
seconds. There is also a special script which will take a single exposure at the fastest possible exposure time of
1500 milliseconds (mS) immediately upon execution.
N.B.: FLAMINGOS has two integration timers, a milliseconds timer for exposure times ≤ 60 seconds, and a
seconds timer for exposure times ≥ 60 seconds. The seconds timer was determined to have a total timing error
range of ~ 1 second
4
; the array controller hardware code was updated during August 2003, and this problem
should have been eliminated; however, we have not yet evaluated the engineering data. Some observers choose
to use 60 seconds as the maximum exposure time they will use for their observations, in order to use only the mS
timer.
The default bias for imaging is 1.0 V; the present value may be obtained by hitting the Update All Items
button on the UFSTATUS GUI. The MCE4 array controller supplies this bias automatically on boot, after
initflam.pl has been executed.
The general outline for imaging observations is as follows:
1. Set Instrument Position Angle.
2. For every new target, verify telescope pointing on a SAO or Fixed Bright star close to the target position.
Do so by imaging the star on FLAMINGOS; offset the telescope until it is well centered on the array, then
have the telescope operator Z the telescope (cf. § III. Nightly Startup Tasks: B. Startup on the sky).
3. Acquire target close to the center of the FLAMINGOS field of view (FOV).
4. Check focus.
5. Execute imaging dither pattern.
6. Repeat steps 1 – 5 on standard; we usually use the Persson standards (see the FLAMINGOS binder). The
telescope operator's cache identifies these as HST/NICMOS standards.
7. Take any required dome flats. These may be done in the afternoon.
8. Take darks (~20 each) at every exposure time that was used. These may be done in the afternoon.
The following list of commands is useful for imaging and for spectroscopy (described in the next section). A
more detailed explanation of several of these scripts directly follows the list.
3 In the in the H and K-bands the emission is mostly generated by OH in the atmosphere at elevations of 90 km.
4 Mark Dickinson discovered this problem. See his analysis at: www-int.stsci.edu/~med/flamingos/fewompt_plus.html.
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