Results 1 to 3 of 3
  1. #1
    Ed L.'s Avatar
    Ed L. Guest

    Default First light on Homemade 80mm Achro



    From a variety of Surplus shed parts, and some home depot trips, I've
    managed to cobble together a little 80mm f/5 scope.

    As with any first time project, when I put it under the stars, I had some
    issues. The first one was my culmination was awful. I made some changes,
    and made the culmination adjustable, and now I have nice circular stars (for
    the center stars) when I go unfocused on either side of focus.

    What I have now figured out, is that I have some very serious coma, all
    those nice seagulls are pretty far from the water when I'm looking through
    the scope.

    My question to any takers out there, what is the best approach for
    correcting coma? You can assume that all the mechanical parts are
    adjustable for me.

    Also, I was expecting to see the violet fringing around bright objects.
    What I was not expecting was a green fringe!?! Have I messed something up,
    or are my focal planes off, or, is my objective worth what I paid for it?

    Thoughts? Suggestions?

    Thanks,

    Ed L.



  2. #2
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default First light on Homemade 80mm Achro

    >

    Sounds like an interesting project, hope you get it sorted out. Makes you
    believe in those inexpensive Chinese scopes a bit more...

    Coma=collimation....

    jon

  3. #3
    Lurking Luser's Avatar
    Lurking Luser Guest

    Default First light on Homemade 80mm Achro

    "Ed L." <eladner@nospam.yahoo.com> wrote in message news:<zhA_b.111399$jk2.496927@attbi_s53>...

    Sorry if this reply is too late, but I am posting through Google.

    It sounds like you built the same scope I did. It works great as a
    spotting scope, but I have noticed the same coma problem with it.
    Lenses are spherical and will tend to have a pronounced coma with fast
    scopes like an f/5. And I think that this lens in particular is not
    well corrected, but hey, you get what you pay for. I have found that
    using a 3x Barlow helps somewhat, simply by increasing the focal
    length. They make coma-correcting lenses, which are very thin and
    almost flat, but I think they tend to be pricey.

    Not sure if this would work, but you might try masking the outer edge
    of the lens (or should it be a center dot?). Of course you will lose
    some aperture that way.

    Good luck and let me know if you get it corrected,
    James King

 

 

Similar Threads

  1. M27 Unguided First Light CGEM mount with Meade 80mm 5000 APO
    By DaltonSkyGazer in forum CCD Imaging Forum
    Replies: 8
    Last Post: 07-16-2010, 03:17 AM
  2. Skywatcher ED 80mm first light report.
    By Dublin sky watch in forum Refractor Telescopes Forum
    Replies: 5
    Last Post: 06-13-2010, 05:03 PM
  3. 152 achro vs 127 apo
    By lalunanelpozzo in forum Refractor Telescopes Forum
    Replies: 4
    Last Post: 06-03-2010, 01:58 AM
  4. 2nd light ver. 1 SSP color and Explore Scientific's 152 mm Achro
    By Craig in forum Amateur Astronomy Forum
    Replies: 0
    Last Post: 06-28-2009, 03:54 AM
  5. Mak-Newt vs D&G achro
    By John Adlington in forum Amateur Astronomy Forum
    Replies: 12
    Last Post: 01-02-2004, 04:40 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.0
Powered by vBulletin®
All times are GMT. The time now is 07:44 AM.