Sigma QUick Infrared Camera manual System Overview, Near-Infrared Observing Techniques

October 30, 1997 1

1 System Overview

The University of Hawaii (UH) QUick Infrared Camera (QUIRC) utilizes a 1024 ￿1024 pixel HgCdTe Astronomical Wide Area Infrared Imaging (HAWAII) array produced by Rockwell Science Center. This array is sensitive to radiation from 1 to 2.5 ￿m. The reimaging optics provide a 1:1 scale, giving the pixel scales listed in Table 1 for the various telescopes and configurations.

Table 1. QUIRC pixel scales

Telescope	Optics	arcsec/pixel	FOV (arcsec)
UH 88-inch	f/10	0.1886	193x193
	f/31	0.06084	62x62
CFHT	f/8	0.150	154x154
0.61-m	f/15	0.43	440x440
QUIST 0.25m	f/10	1.5	1550x1550

The QUIRC system is comprised of four functional components: (1) the detector, optics, and dewar;

(2)The detector readout electronics; (3) A DSP controller; and (4) the instrument control Sparcstation and fiber optic communications interface. The first three components are physically integrated and mounted on the telescope, while the fourth is typically located in the observing room and/or the computer room.

The QUIRC electronics are controlled from a Sparcstation by issuing commands and receiving data via fiber optic cables. The control program on the Sparcstation is called “qcdcom”. The qcdcom program is based on the ccdcom program by M. Metzger and was modified for use with QUIRC. The qcdcom program controls taking exposures and writing data in FITS format to disk, operates the moving parts of the instrument such as the shutter, filter wheel, and pupil mask, communicates with the telescope and guider to obtain information and perform mosaics, and provides a script capability for automatically performing simple observing tasks. qcdcom is a command line interface only and does not directly provide image display, but can be used with any popular display program that can read FITS files (e.g. saoimage, Vista, IDL). A link has also been provided to the viewfits program to automatically display images (see below).

2 Near-Infrared Observing Techniques

Imaging in the near-infrared (1–2.5￿m) generally requires more effort than at optical wavelengths, because the background is so much higher. There are two general data reduction techniques in common use—both of these require frequent observation of sky fields.

The first data reduction philosophy is one in which the sky fields are used for subtraction, and the sky subtracted image is divided by normalized dome flats to remove the variations in quantum efficiency. The advantage of this technique is that the dome lights have similar color temperature to the typical sources being studied.

The second data reduction technique is one in which the sky exposures are also used as flats, so the image is sky subtracted, then divided by a normalized sky flat. This technique often will work better