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#121
February 18th 04, 03:35 AM
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New Huge Celestron 20" PICS up at Astromart
Thanks Roland, I'll do that. I haven't bought an new astronomy book in over
a month ... "Chris1011" wrote in message ... Roland, if you have the time, Sorry, I don't have time. Heading out today, won't be back for a while. You can see the pros and cons in Rutten. All systems are described quite well. It comes down to large CO = low off-axis aberrations. RC 
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#122
February 18th 04, 02:07 PM
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New Huge Celestron 20" PICS up at Astromart
I recommended they use the Optec system and change out the secondary holder
to a non expansive material. "Revolutionary Optical System a.. .5 meter (20") corrected Dall-Kirkham telescope (CDK) b.. Astrograph - Pinpoint star images to the corner of a 35 mm frame (great for imaging and visual) c.. 200 percent more light-gathering power than a 14" d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes e.. Conical Primary Mirror - Low thermal mass so the primary mirror equilibrates quickly " Their words above. They did agree that they will be making oversized mirrors and masking the edge to eliminate/reduce TDE. Are you doing that now? Thanks Herb ATWB "Yuri" wrote in message om... "Herb York" wrote in message ws.com... They use a corrector to get a 42mm flat image circle 12.5 micron at edge according to the engineer and f 6.8 and a masked oversized mirror to reduce/eliminate TDE. http://www.buytelescopes.com/product...5&display=desc Thank you Herb ATWB Hi Herb, At f/6.8 focusing/defocusing during exposition may be an issue, what focuser do they use? Also what is the primary mirror substrate? Yuri
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#123
February 18th 04, 02:07 PM
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New Huge Celestron 20" PICS up at Astromart
I recommended they use the Optec system and change out the secondary holder
to a non expansive material. "Revolutionary Optical System a.. .5 meter (20") corrected Dall-Kirkham telescope (CDK) b.. Astrograph - Pinpoint star images to the corner of a 35 mm frame (great for imaging and visual) c.. 200 percent more light-gathering power than a 14" d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes e.. Conical Primary Mirror - Low thermal mass so the primary mirror equilibrates quickly " Their words above. They did agree that they will be making oversized mirrors and masking the edge to eliminate/reduce TDE. Are you doing that now? Thanks Herb ATWB "Yuri" wrote in message om... "Herb York" wrote in message ws.com... They use a corrector to get a 42mm flat image circle 12.5 micron at edge according to the engineer and f 6.8 and a masked oversized mirror to reduce/eliminate TDE. http://www.buytelescopes.com/product...5&display=desc Thank you Herb ATWB Hi Herb, At f/6.8 focusing/defocusing during exposition may be an issue, what focuser do they use? Also what is the primary mirror substrate? Yuri
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#124
February 18th 04, 02:09 PM
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New Huge Celestron 20" PICS up at Astromart
"Herb York" wrote in message ws.com...
They use a corrector to get a 42mm flat image circle 12.5 micron at edge according to the engineer and f 6.8 and a masked oversized mirror to reduce/eliminate TDE. http://www.buytelescopes.com/product...5&display=desc Thank you Herb ATWB Hi Herb, At f/6.8 focusing/defocusing during exposition may be an issue, what focuser do they use? Also what is the primary mirror substrate? Yuri
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#125
February 18th 04, 02:09 PM
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New Huge Celestron 20" PICS up at Astromart
"Herb York" wrote in message ws.com...
They use a corrector to get a 42mm flat image circle 12.5 micron at edge according to the engineer and f 6.8 and a masked oversized mirror to reduce/eliminate TDE. http://www.buytelescopes.com/product...5&display=desc Thank you Herb ATWB Hi Herb, At f/6.8 focusing/defocusing during exposition may be an issue, what focuser do they use? Also what is the primary mirror substrate? Yuri
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#126
February 19th 04, 02:21 PM
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New Huge Celestron 20" PICS up at Astromart
"Herb York" wrote in message ws.com...
I recommended they use the Optec system and change out the secondary holder to a non expansive material. d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes -If primary mirror made of Pyrex, refocusing may be needed anyway, CarbonFiber will not help. Yuri
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#127
February 19th 04, 02:21 PM
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New Huge Celestron 20" PICS up at Astromart
"Herb York" wrote in message ws.com...
I recommended they use the Optec system and change out the secondary holder to a non expansive material. d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes -If primary mirror made of Pyrex, refocusing may be needed anyway, CarbonFiber will not help. Yuri
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#128
February 19th 04, 03:05 PM
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New Huge Celestron 20" PICS up at Astromart
My opinion is you need to focus any system - between filters using CCD for
example. They will make it able to focus. Thanks Herb ATWB "Yuri" wrote in message m... "Herb York" wrote in message ws.com... I recommended they use the Optec system and change out the secondary holder to a non expansive material. d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes -If primary mirror made of Pyrex, refocusing may be needed anyway, CarbonFiber will not help. Yuri
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#129
February 19th 04, 03:05 PM
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New Huge Celestron 20" PICS up at Astromart
My opinion is you need to focus any system - between filters using CCD for
example. They will make it able to focus. Thanks Herb ATWB "Yuri" wrote in message m... "Herb York" wrote in message ws.com... I recommended they use the Optec system and change out the secondary holder to a non expansive material. d.. Carbon Fiber Truss - Increases stiffness and minimizes the need to refocus due to temperature changes -If primary mirror made of Pyrex, refocusing may be needed anyway, CarbonFiber will not help. Yuri
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