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Proceedings Paper

Operation Of The CCD/Transit Instrument (CTIi)
Author(s): J. T. McGraw; M.G. M. Cawson; M. J. Keane
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Paper Abstract

The CCD/Transit Instrument (CTI) is a unique, fully-automated imaging survey telescope now in routine operation on Kitt Peak Mountain. This telescope, which has no moving parts, uses two charge-coupled devices (CCDs) aligned east-west in the focal plane. The CCDs are operated in the time-delay and integrate (TDI) mode at the apparent sidereal rate to produce a strip image of the sky 8.25 arcminutes wide in declination and eight hours of time in length. In this way, about 15 square degrees of the sky are surveyed every clear night. After a year, more than 40 square degrees will be surveyed in a continuous strip. Every clear night the CTI produces a V-bandpass image from one CCD to a limiting magnitude of V = 21 while the other CCD observes in the U, B, R or I bandpass, depending upon the sky brightness. Over several years, during which the telescope will not be moved, the digital CCD data can be registered and added to produce an image to fainter limiting magnitudes. Astronomical programs addressed by the CTI include the refinement of the supernova production rate by simply counting them as they occur over a number of years, the detection on the rise to maximum of several bright (Vmax < 16) supernovae per year, and the definition of a complete sample of quasars to faint limiting magnitude using as the primary selection criterion V-bandpass variability, with color as a secondary criterion. Other scientific programs addressed by CTI data include galactic structure investigations based on multi-color star counts to faint limiting magnitude, searching for solar/stellar variability at the millimagnitude level by precision photometry of the brightest unsaturated stars, galaxy counts and correlation functions in an "image without edges" (in one dimension), and the investigation of the statistics and galactic distribution of variable stars of all types. The CTI is now in routine operation. We report on the performance of its unique bi-metallic thermally self-compensating structure, its three-mirror wide-field optical system and its mode of operation. We also present an overview of the CTI data-handling system which is generating and absorbing up to 450 megabytes of image data on a daily basis and updating data bases at this rate. Both the real-time acquisition computer system and the reduction, analysis and archival computer systems are described. The role of the CTI as a prototype for future specialized, low-cost telescopes is discussed. Implications for successfully handling the vast amount of data produced by CTI for future large telescope data systems are reviewed.

Paper Details

Date Published: 13 October 1986
PDF: 10 pages
Proc. SPIE 0627, Instrumentation in Astronomy VI, (13 October 1986); doi: 10.1117/12.968073
Show Author Affiliations
J. T. McGraw, University of Arizona (United States)
M.G. M. Cawson, University of Arizona (United States)
M. J. Keane, University of Arizona (United States)

Published in SPIE Proceedings Vol. 0627:
Instrumentation in Astronomy VI
David L. Crawford, Editor(s)

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