Loading ...
Sorry, an error occurred while loading the content.

Re: [ATM_Optics_Software] Re: Revised Petzval Design (Ptz01-02)

Expand Messages
  • Alan French
    ... Roman, Short focal lengths are nice because they allow wide fields. Another big advantage, to me, is the shorter tube length. If a 6 f/4 is as long as a
    Message 1 of 45 , Mar 19, 2006
    View Source
    • 0 Attachment
      >
      > It was not my post but I will answer anyway...
      >
      > What is wrong with short EFL? Why 6" f/4 apo telescope is worse than
      > 6" f/8 one if OTA lengthes are equal? High relative aperture is
      > definitely good for CCD imaging. You are always can use cheap
      > 2x barlow lens for 6" f/4 apo but you will have problems with 2X focal
      > reducer with 6" f/8 telescope.

      Roman,

      Short focal lengths are nice because they allow wide fields. Another big
      advantage, to me, is the shorter tube length. If a 6" f/4 is as long as a
      6" f/8, then it is not as portable and not as easy to mount as a 6" f/4 that
      is 24 inches long. The big advantage of a short tube is gone.

      Clear skies, Alan
    • rflrs2000
      ... Another possibility I ve recently encountered is a variation of the Schupmann. While the lens tilts probably won t let it be pushed for speed, it can be
      Message 45 of 45 , Jul 20, 2007
      View Source
      • 0 Attachment
        --- In ATM_Optics_Software@yahoogroups.com, chris1011@... wrote:
        >
        > In a message dated 3/17/2006 5:31:03 PM Central Standard Time,
        > dschaack@... writes:
        >
        >
        > > Many years ago I asked a question in this newsgroup about possibility
        > > of the correction of secondary spectrum with standard glasses,
        >
        > I think you can, but the designs always seem to come out with very long
        > distances for short EFLs.

        Another possibility I've recently encountered is a variation
        of the Schupmann. While the lens tilts probably won't let it
        be pushed for speed, it can be compact relative to the focal
        length, e.g.(145 mm f/10):

        http://users.rcn.com/rflrs/Schupmann01-50x.len OSLO input file
        http://users.rcn.com/rflrs/Schupmann01-50x.prg KDP input file
        http://users.rcn.com/rflrs/Schupmann01-50x.txt TEXT prescription
        http://users.rcn.com/rflrs/Schupmann01-50x.zmx ZEMAX input file
      Your message has been successfully submitted and would be delivered to recipients shortly.