[ATM] [atm] how to test flat secondary mirror

[Francis J. O'Reilly]

Seyyed:

Thank you for your reply. I'm glad to try to assist you with your project. I'm 49 years old. I live In New York, and I have made several telescopes during my life. I am working on an optical flat project right now. I am grinding three seven inch (~175mm) optical flats. I have just entered the final stage of fine grinding and hopefully will start polishing this weekend. I am making the flats on both surfaces. Over the weekend, I taped a grinding session. I am posting it to You Tube (As soon as my daughter can figure out how to do it for me) I will keep you posted on my progress.

I will try to scan in some documents that are in the public domain for you. I do not want to violate copyright laws. ATM II should be in the public domain by now. Can you open adobe files (.pdf format) on your computer?

If you send me a mailing address offline (Do not post it to the list) I will also try to mail you some information, to the extent that it does not violate any embargos that may be in place.

I hope that these types of endeavors help to unite our cultures by emphasizing that which we have in common rather than that which distinguishes us.

Best regards,

Francis J. O'Reilly
  ----- Original Message ----- 
  From: seyyed mahmoud ghasemi 
  To: Francis J. O'Reilly 
  Sent: Tuesday, August 28, 2007 8:21 AM
  Subject: Re: [ATM] [atm] how to test flat secondary mirror


  DEAR FRANCIS J. O,REILLY,

  THANK YOU VERY MUCH FOR YOUR EXPLANATION AND HEREBY I APPRECIATE SO MUCH.....AS I CANNOT ACCESS SUCH  WORTHWHILE  BOOKS THAT YOU INTRODUCED  ,I WILL BE GRATE FULL IF YOU WOULD DO ME A FAVOUR AND  SEND ME  SOME USEFUL ARTICLES  IN THIS RESPECT IN DETAILS  SPECIALLY THE ONE  WHICH HAS BEEN  DESCRIBED IN  AMATEUR   TELESCOPE MAKING  II  ....

  THANKS IN ADVANCE ...
  NOW ABOUT MYSELF:
  I AM AN IRANIAN  MAN ,WITH 47YEARS OLD AND FULLY INTERESTED IN  TELESCOPE MAKING ...RIGHT NOW  I HAVE  MADE A GOOD  SPHERICAL MIRROR  AND MY TELESCOPE IS IN FINAL STAGE OF MAKING  ...THATIS WHY I AM  READY TO START A NEW  TELESCOPE AS MY SECOND PROJECT  AND IT IS  GREGORIAN ONE  ...I AM VERY EAGER TO MAKE IT  BUT I AM PREPARING THE NECESSARY INFORMATION ABOUT THE SECONDARY MIRROR  AND  FLAT MIRROR AND SO ON ...
  IN THIS WAY I WILL BE GRATEFUL TO HEAR FROM YOU AND  GIVE ME THE NECESSARY INFORMATION IN THIS NEW PROJECT...IF YOU HAVE SOME INFORMATION ELSE ABOUT ME  PLEASE LET ME KNOW ....

  YOUR COOPERATION IN THIS RESPECT WILL BE LONG REMEMBERED ..

  FAITHFULL YOURS,
  S.M.GHASEMI  

  "Francis J. O'Reilly" <foreilly at verizon.net> wrote:
    Interesting question.

    Flats are generally tested using a reference flat, that is another flat 
    known to be flat to a specific tolerance.

    The reference flat is put on bottom, the flat being tested is put on top, 
    with the fface being tested in contact with the reference. A monochromatic 
    light is shined on the pair and interference fringes or Newton Fringes are 
    shown. The straightness of the Newton Fringes will show how close your test 
    surface is to your reference surface. There are many books that will show 
    you how to conduct this very basic test as well as how to make a tester. 
    Amateu Telescope Making II has an excellent section on making optical flats, 
    as does Norman Reimer's book, Making a Refractor Telescope. This book was 
    recently published and is available from Willmann Bell, www.willbell.com

    Now, It's our turn.

    I have not noticed any previous posts from you on the list, and from the 
    time stamp of your post, I presume that you are not in the USA. I am 
    interested in hearing about your telescope project, and what types of 
    telescopes that you may already have. Would you please tell the list about 
    yopur telescopes and projects as well as a little about yourself?

    Kind regards,

    Francis J. O'Reilly
    Brewster, New York, USA
    ----- Original Message ----- 
    From: "seyyed mahmoud ghasemi" 
    To: 
    Sent: Sunday, August 19, 2007 1:13 AM
    Subject: [ATM] [atm] how to test flat secondary mirror


    > dear sirs,
    >
    > would you please guide me how to make and polish a flat mirror and 
    > how to test ( if it is exactly flat ) for secondary mirror
    >
    > i appreciate your guidance in advance
    > faithfully yours,
    >
    > s.m.ghasemi
    >
    >
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