Previous Article Next Article Table of Contents


SQIIDing at the McMath-Pierce (1Dec95) (from NSO, NOAO Newsletter No. 44, December 1995) In late September and early October, NOAO's Simultaneous Quad-Color Infrared Imaging Device (SQIID) was used for solar observations for the first time. For several years, SQIID has been highly effective in its principal role as a wideband (JHKL') imager at night. At the inspiration of Ian Gatley and with help from many quarters (including Tim Ellis, Bruce Bohannan, Nick Buchholz, Jerry Heim, Dick Joyce, and Mike Merrill), SQIID trekked over to the McMath-Pierce Telescope to carry out multiwavelength photometric imaging of solar magnetic flux concentrations (or faculae). Because the magnetic pressure in kilogauss flux tubes is comparable to the photospheric gas pressure, flux tubes are largely evacuated (to maintain lateral pressure balance) and have a temperature-vs-height profile very different from the non-magnetic atmosphere. Infrared photometry can elucidate this structure at the deepest observable layers. After what felt like a titanic struggle with stray light, ghost images, and consequent flat-fielding problems, we obtained science-quality images in three narrow (10-50 nm) bands centered at 1075, 1640, and 2100 nm; the longest wavelength channel had to be sacrificed to get reasonably balanced signals in the other three channels. In addition to the scientific results it is expected to provide, this SQIID run was a proof-of-concept that nighttime NOAO instruments based on closed-cycle cryogenic cooling and the WILDFIRE array controller--including the next generation of instruments based on the large-format Aladdin InSb arrays--can be used effectively and practically for solar observations. [Photo not included] SQIID (dark cylinder in the middle surmounted by a heat shield) astride the McMath-Pierce main spectrograph table. Doug Rabin, Dave Jaksha
Previous Article Next Article Table of Contents