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DAVIDG
Pooh-Bah
Reged: 12/02/04
Posts: 1446
Loc: Hockessin, De
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Re: The 'Best' telescope and eyepieces
07/02/08 09:38 AM
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If you want the "best" telescope, it should be unobstructed for the highest possible contrast. Have a f-ratio of 8 or greater, so it does cause problems with the choice of an eyepieces. Have the least amount of surfaces. Have surfaces that are spherical for easy testing to achieve a perfect null. Be diffraction limited over 1/4 degree of view and have flat or nearly flat focal plane.
Given the above one should consider a Schiefspiegler, since the two mirror design can use two mirrors of equal radius and spherical surfaces. Just a bit more difficult to make then a standard newtonian, since the tool for the mirror becomes the secondary. In my opinion it's easier since all the surfaces are spherical and you can easily test for a null. Plus it is unobstructed system which is critical for the achieving the highest contrast.
Then there is a Schupmann medial refractor which is made from two pieces of the inexpensive BK-7 crown glass, and is perfectly color corrected, much better then a APO. It also has a version with all spherical surfaces. Has very close to a perfect MTF curve for ultra high contrast. It can be diffraction limited for all colors over 1/2 degree field of view and of course is unobstructed.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics
Engineering = Taking what you have and making what you need.
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