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astrogeezer41
super member
Reged: 08/27/10
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Re: Edmund 4.25” Deluxe Space Conqueror
[Re: ed_turco]
#5556454 - 12/05/12 09:20 PM
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Hi Ed,
I agree with you about using a .75" elliptical secondary in
a Newtonian (if possible). That's how I designed my 6"f/8
Planetary Newtonian and the results have been great for 30+
years. It should be even easier in an f/10 scope. Great contrast.
-Robert
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ed_turco
Pooh-Bah
Reged: 08/29/09
Loc: Lincoln, RI
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Re: Edmund 4.25” Deluxe Space Conqueror
[Re: astrogeezer41]
#5558039 - 12/06/12 06:33 PM
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I would use a 1" on a 6" f/8; after all it is only 16% obstruction.
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astrogeezer41
super member
Reged: 08/27/10
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Re: Edmund 4.25” Deluxe Space Conqueror
[Re: ed_turco]
#5558313 - 12/06/12 09:24 PM
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Back then the wisdom was (Texereau, Thompson) to get the CO less than 15%. The .75" gave only 12.5%.
It was very hard to make this work and I had to use a slightly smaller diameter tube and a very low profile helical focuser to make it work. There was very little wiggle room in the separation of the primary and the objective. But somehow I made it work.
In this "real world" I am sure a 1" would have worked just fine and saved me a lot of headaches. But I like the results I got for all my efforts!
Thanks,
Robert
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