The current Imager detector is S2KB, a thinned Tek/STIS 2048x2048 CCD with 21 micron pixels. The default gain is 2.8 electrons/ADU. The read noise is roughly 8 electrons RMS. The plate scale is 0.195 arcsecs/pixel yielding a field-of-view of 6.8 x 6.8 arcmins.
The median R-band WIYN Delivered Image Quality (DIQ) for the period June 94 to present is 0.8" FWHM. The median R-band DIQ was 0.7" FWHM or less 25% of the time and 0.6" FWHM or less 10% of the time. We are confident that for nights with DIQ of 0.6" or larger, closed-loop guiding does NOT degrade the DIQ. We do NOT have enough data yet to understand the impact of our current closed-loop guiding system for nights when the DIQ is 0.6" or less.
Standard Harris UBVRI (w001 - w005) and Gunn uvgri filters (w006 - w011), as well as three narrow-band H-alpha filters (w012 - w014), are available. Further information about these filters including filter characteristics and transmission curves are available via anonymous FTP (ftp ftp.noao.edu).
Other filters may be available from the KPNO collection by specifying the needed filters in the Target Table of the observing proposal. Investigators may provide special filters as well. We can support square 2 x 2 inches and 4 x 4 inches filters without special notification. If your filters are not square or not one of these sizes, please note that in your proposal.
Based on extensive testing, we have concluded that for the UBVRI filter set, domeflats work better than twilight flats when tested against the nightsky. We will acquire only dome flats as part of the default calibration process (see below). Queue program investigators may request twilight flats if they desire them. We do not have enough data to draw conclusions about flat-fielding through the Gunn filters, but expect this to be similarly true.
S2KB has significant (1%) fringing in Harris I. Observers desiring Harris I or Gunn i data should indicate if fringe correction frames are needed.
The telescope pointing accuracy is about 10 - 15 arcsecs RMS all-sky but less than 1 arcsec RMS for offsets.
Imager proposers should keep the following queue observing default operation and calibration procedures in mind when filling out their proposals.
(1) The default mode of operation for the Imager CCD will be to read out the entire CCD with no on-chip binning at the default gain of 2.8 electrons/ADU. If you require a different mode of operation, please specify the desired mode and justify it in the Experimental Design section of the observing proposal.
(2) If multiple exposures of the same field with the same filter are specified, we will:
(3) All target objects within your program will be assumed to have equal priority UNLESS you specify otherwise in the "Comments".
(1) We will take 9 full bias frames at the start of each night.
(2) We will take five (5) domeflats through each active filter during the preceding afternoon or following morning.
(3) We will take twilight flats for any program which requires large scale flat fielding although we cannot guarantee that they will be taken the night of the program exposure. Note that domeflats appear to work better than twilight flats at WIYN (see comments above).
(4) We will only use 3 - 5 filters per night.
(5) Photometric programs will be calibrated using a minimum of 12 Landolt (approximate color range: -0.2 <= B-V <= 1.5), Gunn, or KPNO Spectrophotometric standards, depending on the active filters.
(6) We will observe objects at airmasses of 1.5 or less unless: (a) advised that observations at higher airmass are acceptable; or (2) the objects never rise above 1.5 airmasses.
(7) In addition, we will observe user specified standards as requested. However, these will be considered part of the approved program and must fit within the allocated time. These standards MUST be listed as targets in the Target Tables and should be cross-referenced to their program fields they are calibrating. Please indicate the frequency and timing relative to program objects of special standard star observations.
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Last Updated: 8/2/99, wiynq@noao.edu