View Single Post
  #16  
Old 29-07-2010, 09:51 PM
mental4astro's Avatar
mental4astro (Alexander)
kids+wife+scopes=happyman

mental4astro is offline
 
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,997
Quote:
Originally Posted by alistairsam View Post
Hi, is'nt magnification a function of the focal length of the primary and the eyepiece, so how would the magnification of an F4 be the same as an F6?
how do you calculate magnification when using prime focus photography as there is no objective lens, and in this scenario, does the magnification change between an F4 and F6?
.

As bojan said, magnification is the ratio between focal length of the primary and the focal length of the eyepiece.

Hence, as an example, we have two scopes both 8", one f/4, focal length (fl) 800mm, the other f/6, fl 1200.

You can achieve the same magnification with each by using the appropriate eyepiece:

1200 / 30mm = 40 X mag.

800 / 20mm = 40 X mag.

Now, if you use the same EP in each scope, you do get different magnification:

1200 / 30mm = 40 X mag.

800 / 30mm = 27 X mag.
Reply With Quote