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Direct Imaging Improvements (1Mar94) (from KPNO, NOAO Newsletter No. 37, 1 March 1994) During the past semester we have significantly upgraded the direct imaging capabilities at both our largest and smallest telescopes. As described in the following two articles, we have implemented the scan-table for large chips (e.g., the Tektronix 2048 x 2048) at the 4-m and provided a new filter-bolt and shutter assembly at the Burrell Schmidt. In addition to these, we are currently in the process of a major revision to the direct imaging manuals at the 4-m, 2.1-m, 0.9-m, and Burrell Schmidt, combining them all into a single document. The new manual provides as much information as we have been able to gather: what the focus differences are between the various filters; what the focus change with temperature and zenith distance is; improved measurements of the actual count rates at our various telescopes; and all the "village wisdom" about flat fielding (what works and what doesn't) that we have been able to gather from staff and visitors. We hope this document will now be a more useful reference at the telescope, as well as aiding potential users at the proposal-writing stage. This manual (and its supplemental operational guides for the 0.9-m and Burrell Schmidt telescopes) will be available via anonymous ftp to "ftp.noao.edu" and can be found in the subdirectory kpno/manuals. As an additional tool for planning, Frank Valdes of the IRAF group has also updated and improved the "ccd exposure guide" task ccdtime; the new routine now permits calculating exposure times for the various Kitt Peak telescope and CCD combinations as a function of SNR, bandpass, and lunar phase. We find this task invaluable. It will become generally available once IRAF V2.10.3 hits the streets; in the meanwhile, it can be run from any visitor account downtown. There has been a slight revision to the CCD acquisition software ICE ("IRAF Control Environment") which makes it even easier to analyze focus frames for direct imaging. Consult the ICE manual for further details! Finally, as a reminder, we list here the (measured) plate scales and field-of-view of standard direct imaging telescope and CCD combinations. FOV Scale Telescope/CCD f-ratio (arcmin) ("/pixel) 4-m + T2KB 2.8 16.0 x 16.0 0.470 2.1-m + T1KA 7.5 5.2 x 5.2 0.305 0.9-m + T2KA 7.5 23.2 x 23.2 0.680 0.9-m + T2KA 13.5 13.1 x 13.1 0.384 Schmidt + S2KA 3.3 65.0 x 65.0 2.028 Phil Massey
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