text: If you are in a dark place, I'd suggest 50mm. They collect more starlight and are able to bring out some more of the dimmer stars. The other main question is which magnification to use. Both 7x and 10x are pretty standard for astronomy, although the 10x are harder to keep steady if you are only holding them by hand (rather than using a mount). If you are in a city, 35mm may give as good as you can get simply because the light from the city will wash out anything interesting. :(\n\nAlso, check for multicoating on all the surfaces. This will dramatically increase the amount of light that gets through and is very worth it! (I have 7x50 and 10x70 myself)