PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 09 Dec 2003 S.A.McLaughlin Creation 25 Jan 2004 S.A.McLaughlin Resolved liens " OBJECT = INSTRUMENT INSTRUMENT_ID = "LO72CCD" INSTRUMENT_HOST_ID = "LO72" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "LOWELL 72IN VISUAL CCD CAMERA" INSTRUMENT_TYPE = "CCD CAMERA" INSTRUMENT_DESC = " Instrument Overview =================== The visible-wavelength, direct-imaging CCD system for the Lowell Observatory 72-inch Perkins telescope, as well as the 42-inch Hall telescope, is a set of four CCD detectors that can be moved between telescopes. The CCDs are mounted in dewars filled with LN2, liquid nitrogen. User manuals for the Lowell 72-inch and 42-inch telescopes and the CCD controller software systems are available from the Lowell 72-inch telescope web site: http://www.lowell.edu/Research/Mesa/72inch/ Detectors ========= Four, visible-wavelength, CCD detectors are available for direct imaging, depending on the telescope chosen, the observing schedule, and the type of observation to be made. CCD detectors include: - Loral 2K - SITe 2K - NCCD (Navy CCD) - USNO CCD The summary of the CCD detectors and telescope properties are available at the web site noted above. A brief description each of the four CCDs is reproduced from the web site here. Loral 2K CCD ------------ The Loral 2Kx2K CCD is the default optical imaging device at the 72-inch Perkins telescope. The device is a back-illuminated detector with 15-micron pixels. The field-of-view is 3.2 by 3.2 arcminutes. The unbinned system has a pixel scale of 0.0956 arcsec/pixel. The chip is commonly binned at 2x2 for a scale of 0.191 arcsec/pixel. Other binnings are possible: 3x3 and 4x4 result in pixel scales of 0.287 arcsec/pixel or 0.382 arcsec/pixel, respectively. The chip is linear up to 80,500 electrons or 26,000 ADU at the default gain of 3.1 electrons/ADS and appears to be the same either binned or unbinned. The read noise depends upon the time constant. At the default setting, the read noise is 17 electrons, and the readout time for a 2x2 binned image is 6 seconds. The CCD has good blue quantum efficiency: 35% at 3000 angstroms, 48% at 3500 angstroms, and 79% at 4000 angstroms. A quantum curve can be found at the web site mentioned above. A variety of filters are available including UBVRI glass filters. The 'old' Loral died in early April 2001, and the chip described above was put into service on 17 April 2001. SITe 2K CCD ----------- The SITe 2K x 2K CCD is a back-illuminated detector with 24-m pixels. The CCD can be used either at the Perkins or at the Hall telescope, although by default it is used at the Hall. At the Perkins, its one advantage over the Loral is its larger field of view: 5.2 by 5.2 arcminutes. The system is capable of unbinned operation at 0.153 arcsecond/pixel and 2x2 and 4x4 binned operations at 0.306 arcsecond/pixel and 0.612 arcsecond/pixel, respectively. This chip also has good blue sensitivity. A QE curve can be found at the web site mentioned above. Currently it is not possible to read out a subframe with this system, so the read plus storage time in unbinned mode is long, about 4 minutes. This camera is normally used either unbinned or binned 2x2 on the Hall telescope, and binned 4x4 on the Perkins telescope without any reimaging optics. The SITe CCD is cosmetically good, with two bright columns. At present it suffers from some pattern noise, quite low full well capacity, about 70,000 electrons, and read noise of about 14 electrons. The gain is about 3.6 electrons/ADU. The hold time on the dewar in winter has been seen to be as long as 22 hours. A variety of filters are available including UBVRI glass filters. NCCD and USNO CCD ----------------- These CCD cameras are based on TI 800x800 WFPC 1 CCDs with the Harris electronics. The CCDs are thinned, back-illuminated, and have 15-micron pixels. At the Perkins, the USNO CCD is used with a 4:1 reduction box. The unbinned system has scale of 0.43 arcsecond/pixel and a field of view of 5.7 srcminutes. The reducing optics are glass and have a cutoff wavelength in the vicinity of 4000 angstroms. The USNO CCD is reputed to have better UV quantum efficiency than the NCCD device. The USNO CCD is cosmetically very clean and has an extremely flat bias. The NCCD has a fingerprint on it that is annoying but flattens out well . The major drawbacks of the USNO CCD are that the dewar hold time is in the vicinity of 13 hours. The binning can be changed to 2x2 by flipping a switch in the dewar electronics. A variety of filters are available including UBVRI glass filters. Filters ======= A set of standard UBVRI glass filters are available for use. The prescriptions are: - U: liquid CuSO4 + UG1 [42-inch has UG2] - B: not: 1mm BG12 + 2mm BG39 + 1mm GG385 - V: 2mm GG495 + 2mm BG39 - R: 2mm OG570 + 2mm KG3 - I: Interference filter The Lowell Observatory traced these filters on a Lambda 9 spectrophotometer of NOAO. Filter transmission plots and data, as well as plots of the filter curves convolved with the CCD DQEs and compared to the standard system, are available at the Lowell 72-inch telescope web site: http://www.lowell.edu/Research/Mesa/72inch/ " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "N/A" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END