Re: video tips added to photo tips page at desertsecrets


Message posted by gary on December 01, 2001 at 15:34:22 PST:

I've been fiddling with a CCD camera and a telescope for a while myself. I have the same Orion T to C. Until recently, I had no handy way to do the frame grab. I finally bought a notebook computer that has both firewire and usb. Anyway, a cheap way to frame grab is with the Intel cs430. It is a freebee (or nearly free, I forget) if you use the Intel rebate and buy it at Fry's electronics. The cs430 looks like a PC cam (ala American Pie) but has a RCA connector on the back, which is where you connect your camera.

There are many reasons why you should use B&W over color. One is that in video, the B&W bandwidth (hence resolution) is greater than in color. [This is very involved, but it has to do with the way the chroma signal was piggybacked onto the luminance signal to produce composite video. Now S video gets around that problem somewhat, but costs much more money.] B&W cameras are much more sensitive to light than a color camera IF you are using a single CCD. The color mask greatly reduces the sensitivity. Lastly, a B&W camera has near-IR sensitivity, so it will penetrate haze better. I'm using a P23C that you can read about here:
http://64.132.25.173/servlet/cat/product/PC23C.html

The 1/3inch CCD needs to be put into perspective with the 35mm frame. I'm not sure if the 1/3inch is horizontal or vertical, but for my analysis, let the 1/3 inch correspond to the 24mm dimension of the 35mm film. This is roughly a 3x gain in magnification. This is why you can get away with a 400mm focal length lens, since you need to think in terms of the 1/3 inch CCD and not 3mm film.

I would say that the large SCT is not the best suited telescope for this application for a few reasons. One, the CCD is so much more sensitive than film, so that you don't need the light gathering ability of a large SCT. Second, the CCD is so small that vignetting is not a problem, i.e. you don't need a large secondary mirror to illuminate the tiny CCD or a barlow to perform negative projection to spread out the image over the 35mm frame. Third, the large aperture telescopes will have poorer "seeing" through the 26 miles of turbulant air. I think a much smaller telescope, like a good 3 inch refractor would do a better job.

I'm not looking forward to hiking up Tikaboo with a 7lb notebook in the backpack. A digital camcorder with the ability to record from an external camera would be the way to go.


In Reply to: video tips added to photo tips page at desertsecrets posted by Steve Hauser on December 01, 2001 at 14:23:10 PST:

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