Grasslands Observatory - Essays - Tri-Color CCD Imaging at the Grasslands Observatory

CCD color imaging at The Grasslands Observatory until September 2001 was done with an Apogee AP7 CCD camera. This camera has a very sensitive SITe 512 x 512 chip with 24 micron pixels. An ISIS FW1 filter wheel containing an open slot, a clear filter, and standard R, V, B, and I (near-infrared) Photometric filters was used for all exposures. A Finger Lakes Instrumentation Dream Machine CCD camera combined with a Finger Lakes CFW-1 Color Filter Wheel using Photometric R, V, B filters and an Open slot (O) is now used for color and black and white imaging. The AP7 gave a field of view of 14 minutes. The Dream Machine has a chip with similar quantum efficiency as the AP7, but the chip is twice as large (1024 x 1024) and gives a nearly 28 minute field of view. The Dream Machine is used for color imaging, photometry, and asteroid astrometry and discovery.

Focusing is performed with an Optec TCF (Temperature Compensating) digital electric focuser. The telescope and its associated instruments are operated from a separate building, the "Control Room." This building is a small, one-room, well insulated house with lights, heat, a refrigerator, microwave, futon, chairs, and a Control Console for operating the telescope. At the Control Console, a Pentium 4 2.0 GHz Control Room Computer running under Windows XP is networked to two computers in the observatory. The observatory computers operate the telescope, the CCD camera, the filter wheel, the focuser, and other ancillary equipment. The Telescope Computer in the observatory consists of a Pentium 4 2.5 GHz system running under Windows XP. It operates the CCD camera and the 24-inch telescope control systems. The Dream Machine CCD camera is run with MaxIm DL/CCD.

A Pentium 3 2.5 GHz Guider Computer is also networked to the Control Room Computer and the Telescope Computer. It runs the software and hardware for an SBIG ST-237A CCD camera mounted on a Celestron 8-inch f/10 telescope. The C-8 is attached to the 24-inch telescope, and the ST-237A guider is used for long exposures to correct periodic error drift and other drive errors. The Dream Machine CCD camera creates images that are over two megabytes in size. These are read from the CCD camera over the network directly to the Control Room Computer. In order to take the raw data home for processing, a CD disk writer on the Control Room computer is used to make data disks for long term archival storage and for taking data home.

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