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#1
August 24th 03, 10:21 PM
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ED Cameras lens converted into a telescope?
Has anyone converted (or attempt to convert) a Nikon or Canon ED super telephoto camera lens ( eg. 400mm F2.8, 500mm F4, 600mm F4, 800mm F5.6 or 1000mm 5.6) into a refractor telescope and attach an eyepiece for visual use? If so, how do you increase the back focus so that a star diagonal can be used? The back focus of these 35mm designed lenses are short. Will a barlow lens increase this back focus distance and enables the use of a star diagonal? If it can be done, will the images equal or surpass the normal APO refractors like Takahashi, tele Vue, etc? Any comments? Just thinking aloud. 
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#2
August 30th 03, 04:52 AM
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"Birdie" wrote in message
... Has anyone converted (or attempt to convert) a Nikon or Canon ED super telephoto camera lens ( eg. 400mm F2.8, 500mm F4, 600mm F4, 800mm F5.6 or 1000mm 5.6) into a refractor telescope and attach an eyepiece for visual use? If so, how do you increase the back focus so that a star diagonal can be used? The back focus of these 35mm designed lenses are short. Will a barlow lens increase this back focus distance and enables the use of a star diagonal? If it can be done, will the images equal or surpass the normal APO refractors like Takahashi, tele Vue, etc? Any comments? Just thinking aloud. Camera lenses do not make good telescope objectives (other than for low power viewing). Clear Skies Chuck Taylor Do you observe the moon? Try the Lunar Observing Group http://groups.yahoo.com/group/lunar-observing/
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#3
August 30th 03, 05:21 AM
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Sorry, as I posted this question again, you replied. So please ignore my
latest post concerning this same subject.. Why aren't the ED telephotos not good objectives for astronomy purposes? Because they are not designed for it? Any simple optical explanation that can be easily understood? I am asking in reference specificaly to high end ED 35mm telephotos Vs APO refractors. Thank you. "Chuck Taylor" wrote in message ... "Birdie" wrote in message ... Has anyone converted (or attempt to convert) a Nikon or Canon ED super telephoto camera lens ( eg. 400mm F2.8, 500mm F4, 600mm F4, 800mm F5.6 or 1000mm 5.6) into a refractor telescope and attach an eyepiece for visual use? If so, how do you increase the back focus so that a star diagonal can be used? The back focus of these 35mm designed lenses are short. Will a barlow lens increase this back focus distance and enables the use of a star diagonal? If it can be done, will the images equal or surpass the normal APO refractors like Takahashi, tele Vue, etc? Any comments? Just thinking aloud. Camera lenses do not make good telescope objectives (other than for low power viewing). Clear Skies Chuck Taylor Do you observe the moon? Try the Lunar Observing Group http://groups.yahoo.com/group/lunar-observing/
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