# Difference between first (focal length (fl.) 500 mm, ocular (o.) 10 mm) and second telescope (fl. 1000 mm, o. 20 mm)? (both 50 x)

Magnification is defined as $$f_{objectiv}/f_{ocular}$$. If I had the first telescope with the focal length of 500 mm, ocular 10 mm and second telescope with the focal length of 1000 mm, ocular 20 mm, is there a difference between them? Both of them has 50x magnification.

I want to know if there is any difference in the quality of image, etc.

Thank you for all!

• Can you add each telescope's objective diameter (aperture) to the question? – Mike G Aug 1 '19 at 14:21
• All else being equal (same aperture, same quality of optics) there won't be a difference between them. But long f/ratio (longer focal length with same aperture) does make it easier to fabricate a quality lens/mirror. – antlersoft Aug 1 '19 at 15:01
• @MikeG I am centered only to magnification. – User123 Aug 1 '19 at 17:22