Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stargazing Telescope optical path length vs focal length

Tags:
  1. Mar 23, 2012 #1
    Hi

    I am trying to design a three mirror off axis telescope. The free parameters are the offset between the apertures and distance betwen the surfaces.

    My question is for a system with 'n' elements/surfaces (n=3 in my case) is there a relation between optical path length and focal length of the system.

    I dont want to go too descriptive about this problem. If it might help I can upload a pic in some webpage.

    bala
     
  2. jcsd
  3. Mar 23, 2012 #2
    the distance between well yes`. if you have one eye on a lens and the other open. Eye with more light will give more distance but less focus. some what a distortion ? or a dispacement of light'. i would like to see it
     
  4. Mar 23, 2012 #3
    http://img828.imageshack.us/img828/5718/phyfor.png [Broken]

    In this image 'c' (which i interpret as the optical path distance) and 'f' the focal length can be constrained independently.
    For example when i design a system with high focal length with optical path, and optimise the same in zemax, the system focal length reduces to optical focal length for a design with smallest 'rms' radius.
    I cannot quiet grasp the difference between the two quantities here.
    Thank you for reading.
    I am not convinced that i explained my problem clearly. let me know if i need to clarify any part.
     
    Last edited by a moderator: May 5, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook