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Telescopes - Reflector -> Newtonians	Message format

navee8or

Posted 7/5/2012 8:34 PM (#52874)
Subject: home made 13 inch dob

Regular Junky

Posts: 50

Location: massachusetts usa

Greetings , After being into astronomy for a couple of years I thought I would try my skills at making my own dob. I have a 13.1 in mirror and have it installed in an 18 point cell in a truss style dob. All has been built and I have calculated that the focal length of the mirror should be around 58.95 inches. An f4.5 mirror times the diameter 13.1 =58.95inches. the measurement from the half racked focuser to the secondary is 11.5 inches leaving me 47.45 inches to play with. I have cut the the truss tubes to where I estimate the focal length is. I then put in my lowest power eyepiece and with the focuser racked out all the way I have a beautiful crystal clear magnified image , the tproblem is, it's right side up and not reversed

Does this mean I should continue adjusting in the way I'm going??

or am I missing somethingI didn't think of. Any help that you can provide will be appreciated. Also I just finnished building the scope, I have not collimated it . I hope I have provided all the necessary information. Jerry

JohnM

Posted 7/6/2012 1:25 PM (#52885 - in reply to #52874)
Subject: RE: home made 13 inch dob

Forum Support Admin

Posts: 6041
5000

Location: Wyoming Wind River Range

I knew I'd read this post, but couldn't remember where it was.
I'm not quite sure how you could get a non inverted image out of a newt.
Unless you had an erecting EP?
Have you used this program?
http://www.dalekeller.net/ATM/newtonians/newtsoft/newtsoft.htm
I haven't used the new one, but used the older version for years.
You should try it out and see what it has to show for the parameters you used.

navee8or

Posted 7/8/2012 9:54 AM (#52910 - in reply to #52874)
Subject: Re: home made 13 inch dob

Regular Junky

Posts: 50

Location: massachusetts usa

John M, thanks for responding. First thing I have to say is I'm not into computers that deep so I have no idea how to use any of that material. What I have done is back up about five feet, and start at square one check centering on the spider check squareness on the focusser then the secondary and now I'm on to the primary. So far every one of these check points has had discrepancies I'll get back to let you know how things progress. I have been into astronomy for the past four years and am curious about different facets of this hobby, so far I havebuilt myown go to reflector restored two unitrons, and now taken on the challenge of building my own 13 inch dob. Now I am concentrating on just keeping my eyes in the eyepiece and learning the sky. Clear skies and thank you

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