I feel like starting some home project including my telescope, so here's what I have in mind:

I want to build a "bracket" to fit on the telescope which will basically include two motors. One along the X-axis, and one along the Y-axis. This is the relatively easy part.

The hard part will be to get the exact coordinates from the telescope. What I thought would be perfect would be to put a camera on top of the telescope which will capture the night sky. This will then be compared to a starchart on the computer which will tell me exactly where I'm looking at, and will give me the ability to "direct" the telescope to a different star / object / whatever the case might be.

The question I have is: I noticed that taking a picture of the night sky with "normal" exposure time yields no stars in the taken image. I f I leave the expose long enough, I eventually get a perfect image.

I know that this all depends on how bright the star is, etc... but what would be the nominal exposure time to yield just the perfect result? I don't want to get an image full of little white specs, but instead I just want to get the brightest of the stars, eg: Sirius, Canopus, etc...