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Refractor vs. Reflector ?

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#326 spaceydee

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Posted 02 October 2008 - 12:39 AM

you mean you're seeing JFK on Saturn?? :poke: :lol:
(just kidding!)

#327 dothead

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Posted 04 October 2008 - 11:47 AM

Hi Daniel,

thanks for the very interesting info from Pons.
As for the little residual colour, I think a Baader Semi-APO filter would take care of that.

As I think it's more apropiate, I've continued the TRI-SPACE discussion in the refractor forum.

#328 Daniel Mounsey

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Posted 04 October 2008 - 10:22 PM

Thank you,

Actually the color is hardly even visible on the planets. It's more apparent on brighter stars like Vega for example. Images are etched with hard outlines and the spherical correction is sensational. That's what makes the images so beautiful in this scope. Thanks again for raising an interesting subject regarding the tri-space, it looks like you got some very informative feedback.

#329 dothead

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Posted 05 October 2008 - 08:06 AM

...not the least because of your knowledgeable and first hand exerience reports. Thank you a lot!

Ralph

#330 dothead

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Posted 05 October 2008 - 10:39 AM

Daniel,

did you notice any lateral colour introduced by the sub aperture corrector in Pons' TRI-SPACE scope, especially as you go to wide fields?

Ralph

#331 Daniel Mounsey

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Posted 05 October 2008 - 02:36 PM

Not that I recall. Most of the time when we view with it, it's at very high magnification. I do recall Pons throwing it a large Clave 2" eyepiece. Can't remember the focal length right now but it was pretty low magnification. The images were very beautiful across the field and color wasn't even a factor I noticed. I do recall viewing the stars in the Trapezium somewhere around 700x or 800x. There were six airy discs from light polluted skies with plenty of room around each component. Pons has three different lenses.

10" F-16
9" F-18 designed by Games G. Baker
8" F-20

Pons enjoys the 8" most often and uses that one in the OTA most of the time, but false color for these objectives is not something I'm reminded of when looking through them.

Roland actually made two tri-space correctors for Pons and he still has the extra one. He only uses one and the other just sits in a closet. The entire refractor is a masterpiece. When you see it up close in daylight, it's almost unreal. The 18" Byers gear is a beautiful piece of work, which is surrounded by clear plexy. I really don't know what the exact value is. I sometimes worry about Pons as he's not in the best of health and setting the scope up with a fork lift is a daunting task at his age. :(

#332 dothead

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Posted 06 October 2008 - 06:22 PM

Daniel,

thanks again for some wonderful tidbids of information.

I think I've heard that the Corning France B58-53 glass Roland Christen used for one of the three elements of his corrector is alas no longer available. But Mike I. Jones has just posted in the refractor forum an alternative design for a 3 element corrector which uses available glass types and gives about 1.4 X better colour correction than Rolando's, and also says that this can be improved further by 4 element correctors he also has designed.
Looks like the TRI-SPACE should be the way to go for BIG Apos!

Ralph


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