Seeing statistics at the upgraded 3.8m UK infrared telescope (UKIRT)

Marc S. Seigar, Andy J. Adamson, Nicholas P. Rees, Timothy G. Hawarden, Malcolm J. Currie, Timothy C. Chuter

Research output: Contribution to journalConference articlepeer-review

3 Scopus citations


From 1991 until 1997, the 3.8m UK Infrared Telescope (UKIRT) underwent a programme of upgrades aimed at improving its intrinsic optical performance. This resulted in images with a FWHM of 0″.17 at 2.2 μm in September 1998. To understand and maintain the improvements to the delivered image quality since the completion of the upgrades programme, we have regularly monitored the overall atmospheric seeing, as measured by radial displacements of subaperture images (i.e. seeing-generated focus fluctuations), and the delivered image diameters. The latter have been measured and recorded automatically since the beginning of 2001 whenever the facility imager UFTI (UKIRT Fast Track Imager) has been in use. In this paper we report the results of these measurements. We investigate the relation between the delivered image diameter and the RMS atmospheric seeing (as measured by focus fluctuations, mentioned above). We find that the best seeing occurs in the second half of the night, generally after 2am HST and that the best seeing occurs in the summer between the months of July and September. We also find that the relationship between Zrms and delivered image diameter is uncertain. As a result Zrms frequently predicts a larger FWHM than that measured in the images. Finally, we show that there is no correlation between near-infrared seeing measured at UKIRT and sub-mm seeing measured at the Caltech Submillimetre Observatory (CSO).

Original languageEnglish (US)
Pages (from-to)366-375
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2002
EventObservatory Operations to Optimize Scientific Return III - Waikoloa, HI, United States
Duration: Aug 22 2002Aug 23 2002


  • Facility seeing
  • Sub-mm seeing
  • Telescope optical quality


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