Stage 2 equipment description

I modified my telescope in January 2000 to use a video camera instead of a photographic camera. The basic telescope remains the same as before and a description can be found here. The main change that was required to accomodate the video camera was the addition finder scope. I was always able to use the photographic camera viewfinder as an eyepiece but when the video camera eliminated that I needed a way to get regions of interest onto the camera detector. The finder is an old Meade 60mm f/11.7 refractor with a Thousand Oaks ND 5 glass solar filter and 9mm eyepiece.
The two cables hanging off of the end of the camera are the DC power input and the video coax output cable. The black box to the north of the equatorial mount is a regulated DC transformer. I spliced the white connector that can be seen about a foot from the end of the camera so that I can leave the transformer outside under the clam shell mount cover. The camera lives indoors when not in use. The entire instrument package unscrews at the large square nut at the end of the chromed tube of the focuser. The video cable runs underground through a conduit and into the control room. The loop of cable that can also be seen at the back of the camera is for the shutter speed control.
The video camera is a Pulnix TM-72EX CCD video camera. The PDF file of the data sheet can be found here. The camera uses a 2/3" interline transfer device CCD detector with 768 X 493 pixels. The TV resolution is rated at 570 (H) X 350 (V).
The camera has the usual adjustments of shutter speed, gamma, and gain. I determined the optimal shutter speed empirically and only vary the gain to compensate for different atmospheric conditions. Unfortunately, the gain control is only accessible by the small screw driver adjusted potentiometer that can be seen in the picture. This means that I have to make coarse gain adjustments by looking across 25 feet or so through the open back door of the control room to the monitor. Fine adjustments are made by walking back and forth between the telescope and the monitor. The folks at Adirondack Video are justified in boasting about the remote control box included with their Astrovid camera.
The video Sony 12" B&W video monitor, Sony GV-D300 digital video cassette recorder and Sony IFT-R20 cordless IR receiver are located inside the control room. The windows are tinted with the darkest car window tinting film that I could find to allow good viewing of the video monitor. Even with that I had to install roller shades on the east and west windows to keep direct sunlight out.
The cordless IR receiver is an important link in the system since it allows the video signal to go directly from the camera to the VCR, with no splitting of the video signal. The only downside is that the VCR must either be playing back or recording for a signal to be sent to the monitor. Use of the pause function on the VCR minimizes the amount of wasted tape.

Page Last Updated: 25 February 2001