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FLAMINGOS-I 2001B Image Quality Summary

11 December 2001

Science images taken during the 12-night Flamingos-I run in October 2001 have been analysed to determine the delivered image quality. Analysis was conducted on over 700 frames (of which about 20% were already the combination of individual exposures) with exposure times ranging from 5 to 100s but typically 30s. Point sources were identified automatically and their image size derived by fitting a Moffat profile using the gemseeing task in the Gemini IRAF package. The images typically contain 15 point sources with adequate signal. Data were taken through the near-infrared J (1.25um), H (1.65um), K (2.2um) and Ks (2.15um) filters; the K and Ks results were combined for this analysis. The derived Moffat FWHM were corrected to zenith pointing by sec(z)^0.6, where z is the zenith distance (equivalently, air mass^0.6). Derived FWHM with extreme values, less than 0.15 or greater than 0.7 arcsec were checked by hand.

The histogram below shows the distribution of image FWHM for the three filters. The distributions have median values of 0.37" (J), 0.37" (H) and 0.46" (K).

One night during the run had seeing significantly poorer than average. As part of normal queue execution management only observations at the longest wavelength (K), which is less affected by the seeing, were taken on that night.

A cumulative frequency histogram was constructed from the image quality distributions and is shown below:

Last update September 13, 2002; Phil Puxley