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18-Inch DFM Telescope

SBO Observing Deck

18-Inch Telescope

18-Inch Telescope The 18-Inch telescope was erected on the open Observing Deck of the newly-built Fleischmann Addition of SBO in 1982. It was the first commercial telescope ever built and sold by the just-started DFM Engineering Company.

The telescope was one of the first computer-controlled telescopes of its era. It was originally driven by a DFM-built 8086-cpu based computer, with individual wire-wrapped one-of-a-kind control boards and a memory of about 8 kilobytes. Operator control was via thumbswitch settings, with information displayed by an array of discrete LED characters.

For the first five years, the telescope sat on the open deck, and hence had to be protected from the elements with a clamshell cover. The Observing Deck was subsequently covered with a roll-off roof, shown at left, which also permitted the addition of the 16-inch telescope as well.

Eventually, the telescope control system (TCS) was upgraded to a PC-based system, with familiar keyboard controls and monitor display. The control computer was also linked to an auxiliary PC running The Sky planetarium-style computer control software, plus CCDSoft camera control software, both from Software Bisque. Now, all an operator has to do is to click on a star on the planetarium display, and tell the computer to "go to it" - and in a few seconds, the object is centered in the eyepiece of the 18-inch.

The 18-inch telescope has a unique flip secondary mirror that provides either f/8 or f/16 optical paths - enabling it to be optimized for planetary or deep-sky viewing. Here are the specifications for both of its modes of operation.

Not only can the telescope be used for visual viewing and 35mm photography, it is also equipped with a 4"x5" film holder, internal shutter, and 6" filter holder for large-format astrophotography. But the most popular form of "picture taking" used by astronomy students is with the ST-6 CCD imager from the Santa Barbara Instrument Group.

The most commonly-used and convenient arrangement for CCD imaging is the piggy-back telescope mode. In this configuration, observers are still free to use the main telescope for visual eyepiece observations, while the camera is simultaneously acquiring a nearly-identical view through the 8-inch Celestron riding on top of the 18-inch. Alternate modes include mounting the camera at the focus of the 18-inch itself, and for wide-field shots, piggyback using a 180-mm focal length telephoto lens. Here are the fields-of-view (48K JPEG) for some different camera arrangements.

Most of the images that appear in our SBO Image Gallery were acquired in using the ST-6 camera on the 18-inch telescope - such as the image collection shown below.

ST-6 CCD Images

18-Inch Operations Manual

of the 18-inch telescope and related equipment, available in Adobe Acrobat PDF format

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