Please guide me about galilean telescopes.?

Question

I wanna build a galilean telescope (please don't advise me to buy it or build a dobsonian). I am wondering what will be the best aperture to observe the planetary details and some nebula or distant galaxies. with more field of view. I used skyandtelescope's scope calculator, I put the following

Aperture: 3 inch

f/number: 13.

Objective focal length: 1000 mm

eye piece focal length : 15 mm.

And it says that

Focal Length: 990mm

Magnification: 66x

True Field of View: 0.8° (The full Moon would easily fit into the field of view)

Exit Pupil: 1.2 mm

Theoretical Resolving Power: 1.52 arcseconds

Approximate Limiting Magnitude of Telescope: +12.2 (under dark, moonless skies)

Is it good specification?? Or if you know a better one than please tell me.

Thank you.

Answer 1

3 inches is nothing. it is far too small and it will limit what you can see. forget planetary detail, forget deep sky. more aperture - the more, the better - will make for a more satisfying observing experience.

why are you so set on building a telesscope? there is nothing to be gained unless you have specialized requirements.

Answer 2

Check your local clubs... There are lots of people wanting to build their own scopes and there are usually lots of clubs offering help...  

Answer 3

Look someplace else for a telescope-- this brand is sold in department stores --- pretty pictures on the box-- and 750 POWER printed in bold letters !  Try one of these places: for a Dobsonian type telescope.... in a 6inch or 8inch size.

http://www.telescope.com/control/categor...

http://www.optcorp.com/category.aspx?uid...

At 3 inches you are limited as to deep sky objects you can observe-- given dark skies away from city light pollution-- a 3 inch can show many objects-- BUT APERTURE wins all other things being equal. 6 inch or 8 inch is a good all around size that still allows the scope to be very portable--

Answer 4

I don't think you mean a "Galilean" telescope. Galileo's original telescope design involved a negative lens for its eyepiece, and had an extremely narrow field of view. Early astronomers quickly replaced this with the Keplerian design, which used a positive eyepiece, and had a much wider field of view. Both these designs are really antiquated...probably what you really want to build is an achromatic refractor telescope. This requires an achromatic objective lens (which normally must be purchased, as refractor lenses are much harder to make than reflector mirrors).

I think you need to do a bit more research on telescope designs before undertaking this project, as it sounds as if you don't know much about telescopes. I'd recommend Phil Harrington's Star Ware (Wiley) as a good starting point.