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NOAO Newsletter - KPNO Operations - September 2000 - Number 63

SQIID Begins Science Observations

Mike Merrill

Since the start of science observation in May 2000 at the KPNO 2.1-m, the Simultaneous Quad Infrared Device (SQIID) has been employed 21 nights during 2000A and is scheduled for 73 nights of science observations during 2000B. Before the start of 2000B, we intend to correct the slight focal plane tilt seen in the J channel, establish PAH channel operation, and make assorted software improvements to ease operations. This article outlines the anticipated performance of SQIID for the coming semesters.

The NOAO infrared camera SQIID produces simultaneous images of the same field in the J, H, K, and narrow-band L passbands, using individual 512x512 quadrants of ALADDIN InSb arrays. The observations are generally background (photon statistics) limited. The designated array for each channel is selected for characteristics (read noise, settling time, and dark signal) appropriate to background-limited opera-tion under actual observing conditions for its single filter. SQIID, which serves as its own acquisition camera, is a good match to "point and shoot" observing at the 2.1-m without a telescope operator. The filters are fixed in place; dark slide and window covers are the only moving parts. SQIID employs closed cycle refrigeration instead of liquid cryogens and, in its prior configuration, operated flawlessly for periods as long as 40 days, providing an unparalleled degree of system stability.

SQIID is operated from a Sun workstation through the same NOAO Wildfire system and TCL scripting language employed by Phoenix, IRIM, and CRSP. It is useful to understand that the JHK integration times are identical. Since SQIID is background limited and co-addition is highly efficient, matching the total integration time to the needs of the most demanding channel does not compromise the results in other channels. In like fashion, one can afford to co-add shorter integrations to maintain dynamic range.

Composite SQIID multi-wavelength IR image of M17

Caption: SQIID has returned to Kitt Peak with enhanced capabilities. This composite SQIID multi-wavelength IR image of M17, a region of massive star formation known as the Omega Nebula, was formed by K. M. Merrill to illustrate the potential of the new PAH channel. PAH dust emission strongly dominates in this region. The dust is in emission in response to the UV radiation of newly formed hot, luminous stars. The 540-sec composite JK exposures were taken at the KPNO 2.1-m telescope on 11 May 2000. The PAH data are archival COB data.

The UPSQIID package, a set of IRAF procedures designed to facilitate the reduction of SQIID data sets, is available to process each individual source frame and to combine multiple frames from the individual channels into spatially registered composite images. The UPSQIID package is not an officially released and supported IRAF package. Although specifically targeted for SQIID, the routines are suitable for other image data as well.

For further information contact Michael Merrill (, 1-520-318-8319) or visit the SQIID Web site (

SQIID Performance Characteristics

       KPNO Telescope               2.1-m                       4-m
Plate Scale (arcsec/pixel) 0.68 0.39 Unvignetted FOV (arcsec) 306x320 176x183 Estimated limiting magnitude* point diffuse point diffuse J 19.43 20.38 20.60 20.94 H 18.55 19.55 19.72 20.07 K 18.00 18.96 19.17 19.52 PAH 12.15 13.10 13.31 13.66
(*) S/N = 3 in 60 sec integration time for a point-source (point: mag) and a diffuse-source (diffuse: mag/square arcsec) (T = 50F; 3mm PWV; midrange OH background)

Channel Characteristics  J        H        K        PAH     Units
Conversion gain 10 10 10 11 electrons/adu Applied bias 600 600 700 - mv Full well >2e5 >2e5 >2e5 - electrons Dark <1 <5 < 5 - adu/sec Read noise 40 40 35 40 electrons rms Integration time 0.732 0.732 0.732 - sec miminum Relative pointing (5E,2S) (3E,2N) (0,0) - pixels on sky Typical extinction 0.15 0.06 0.08 - mag/airmass Background (varies) 100 400 740 - adu/sec/airmass@2.1m 10.0 mag star 2.86e4 2.77e4 1.65e4 - adu/sec@2.1m Filter manufacturer Barr Barr Barr Barr Filter HPshort 1.131 1.535 2.027 3.262 µm Filter midpoint 1.267 1.672 2.224 3.299 µm Filter HPlong 1.402 1.809 2.421 3.336 µm Filter FWHM 0.271 0.274 0.394 0.074 µm
J filter data are estimated from the manufacturer's warm tracing by applying 1.63% shortward shift. Other data are from manufacturer's 77K tracings. Dichoric transparency has not been applied.

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