I've got my telescope set up to shoot the eclipse tonight. Obviously, all I can control is ISO and shutter speed, but the telescope has no aperture to speak of and even if it did, the camera isn't controlling it. So, what to use for exposure settings?

Ive only got a 75-300IS to shoot with tonight.

so telescopes don't indicate their aperture? Did you try to search by telescope's model - maybe the aperture is mentioned on the web somewhere?

Does that make it f/11?

If so, what would you recommend as a shutter speed here? That's two stops below f/16, right? So shutter should be two stops faster than 1/ISO? I'll set it to ISO 200 for this, so 1/320?

not sure what the optimal exposure for lunar eclipse is.

But if you were to follow the sunny 16 rule, then at ISO 200 and f/11, your shutter speed would be 1/400

Focusing is the hardest part. As soon as I get my face near the viewfinder, even without breathing, the heat from my face fogs it up. This is total guesswork.

A <a href="http://www.cloudynights.com/item.php?item_id=518">Hartmann mask</a> with either circles or triangles should do the trick.

Thanks. I should do some research before I do trial and error, and error, and error.