I am thinking about purchasing he Canon Rebel Xti.....I am tihnking about what lens to purchase as well and any help will be gretly appreciated! I want to shoot sun shots( sunset and sunrise) and moon shots. I have taken so many of these shots but the moon comes out like a ball and so does the sun(w/ a pnt and shoot cam of course).....These are my main concerns....which means night and day shots...but i want god detail and not ttoooo expensive ($1000 for a lens)......please help me if u can....one more thinngg....is the bel xti a good choice w/ my conditions of the sun and moon? or should i get the 30d? :)

You can do this sort of photography with an XTi. In fact you have the same challenge even if you get a 30D, getting a fast enough lens.

I'd recommend looking at apertures of F/2.8 or faster. Then you need to decide telephoto or prime, since it's the first lens probably telephoto for the versatility. The Canon 70-200 F/2.8 (http://www.bhphotovideo.com/c/product/91680-USA/Canon_2569A004_70_200mm_f_2_8L_USM_Autofocus.html) non-IS is close to your budget but a little over.

The Canon EF-S 17-55mm F/2.8 IS (http://www.bhphotovideo.com/c/product/425812-USA/Canon_1242B002_EF_S_17_55mm_f_2_8_IS.html) would be all of your budget but is a great all purpose lens.

I'm sure others will have ideas on Sigma or Tamron lens that would be better for your budget.