[SERIOUS]Exposure Time

[BillGeek]

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...

[Nightwalker83]

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.

I have heard of this done before! From what I remember from a couple of years ago the people that did this used a small circular camera/device in a holder which was mounted on top of the telescope. The camera/device was then connected up to a laptop which was used to capture the image of what the people was looking at through the telescope. I am not sure how the camera communicated with the laptop whether it was via cable or by wireless.

[MaximilianMayrhofer]

You're seriously wasting your time. Use mathematics. All basic data can be retrieved from existing catalogs.

[wossname]

I'm in agreement with Max on this.

But in any case an exposure of 10 seconds will give you all the Naked-Eye Visible stars and also a few of the brighter non-NEV ones. Much longer than that and you'll end up with lots of unsightly noise in the images.

[BillGeek]

I'm in agreement with Max on this.

But in any case an exposure of 10 seconds will give you all the Naked-Eye Visible stars and also a few of the brighter non-NEV ones. Much longer than that and you'll end up with lots of unsightly noise in the images.

I'll take Max's plan into consideration. I'll struggle a bit with the maths (judged from the link he included in his post) but I'll give it a shot in any case.

As for the exposure time, I actually found this page. Very informative.