Which camera to choose ?

Which one is the better, the 505V or the dsc70, i also want to use the camera for astronomy,

Greetings from Holland

-- Patrick van den berg (pb@vdenberg.demon.nl), July 17, 2000

Answers

Patrick, I work at NASA in photographic and digital imaging, but I must admit that I know nothing about astronomical digital photography (we are a research and development center), but I occasionally do work with astronomers and astrophysicists and I will put your question to them. There seems to be some interest in this subject, so I will try to find out what I can and relay it in this forum.

-- fred (fdeaton@hiwaay.net), July 17, 2000.

Have a look at:

http://www.scancam.com/scancam.html for a very low cost celestial imaging device semi-handrolled from a handheld scanner and a simple timing circuit. It works with both motorized and fixed mounts. With the cost of surplus hand scanners these days it should be a VERY cheap way to go.

You might also try www.ckcpower.com -they sell T mount adapters and monoculars used for long lenses with digicams.

I'm not sure about the relative merits of the scancam article above, but if you like astronomy it looks like a very inexpensive dedicated device that could be a lot of fun to play with. Of course, you'd need to drag a laptop along or toss a parallel port cable out the window and into the back yard... :-) I'm also quite unsure whether you could get a better exposure with a normal digital camera with a bulb or long exposure mode? Obviously, the amount of noise produced by the CCD in the camera during long exposures would be the limiting factor.

You might want to concentrate on digicams that have a dark current subtraction process as part of the long exposure routine. Toshiba's M5, and the new M70 do this with what I'd call stunning results. Basically, it seems that you set the camera for a 1, 2, 4, or 8 second exposure and it takes one and then immediately takes a second one of the same length(?) with the shutter closed(while displaying "processing" on the display...) and uses it to subtract the noise that showed up during the second exposure. I'm not sure just how long an exposure you can use because of the rotation of the earth with a fixed mount? With a tracking mount I guess it'd depend on the accuracy and smoothness of the motion of the tracker -makes me think a continuous drive would be better than a stepped drive for this. You might want to check and see if the Sony models have the dark current calibration type noise subtraction feature for long exposures? I think some Casio models may have a similar feature.

Have fun!

-- Gerald M. Payne (gmp@surferz.net), July 17, 2000.