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FORUMS Photo Sharing & Discussion Astronomy & Celestial 
Thread started 20 Jan 2009 (Tuesday) 07:14
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High FL mirror lenses.

 
Adrena1in
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Jan 20, 2009 07:14 |  #1

Does anyone have a high FL, (400mm to 500mm +), mirror lens? Do you use it much? Have you ever used it for Astrophotography?

Been contemplating a big lens for a while, mainly thinking about glass lenses, but the size and weight is going to be an issue unless I were to get some sort of mount for the lens itself. Occured to me that a mirror lens might be a better idea, what with them being smaller and all that. But I've no idea what the quality is like. Hence the question.

Ta.


Canon EOS 450D, Sigma 18-200mm, Canon 50mm f/2.5 Macro, 2x TC, Revelation 12" f/5 Dobsonian, Mintron PD2285-EX webcam.

  
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PM01
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Jan 20, 2009 16:12 |  #2

400 to 500mm is actually on the low end for telescope. Many are over the 1000mm mark, and the larger reflectors are well over the 3000mm mark.

I use a Meade 14 (3556mm) and a Takahashi 180 Epsilon. Obviously, the Takahashi has better optics and a higher quality mirror.

I do not use mirror optics or mirror lenses for terrertrial photography though. Just way too much flare and scattering of the image to be of any use for my critical standards.

The cheaper mirror lenses leave much to be desired. These are typically in the 500mm f/8 region and are based off the Schmidt Cas design. Not very good at all for image quality. This includes the one made by Sony/Minolta.




  
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Adrena1in
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Jan 21, 2009 02:42 |  #3

PM01 wrote in post #7119391 (external link)
400 to 500mm is actually on the low end for telescope.

Thanks, but I was actually talking about camera lenses rather than telescopes...should've made that clearer. I've got 400mm, 600mm and 1200mm achromatic refractors.

Your last comment does seem to suggest that 500mm mirror lenses aren't worth it, so I won't bother with the Sigma 600mm f/8 I've seen.

Thanks. Gonna have to be a 66mm or 80mm ED APO I think. :)


Canon EOS 450D, Sigma 18-200mm, Canon 50mm f/2.5 Macro, 2x TC, Revelation 12" f/5 Dobsonian, Mintron PD2285-EX webcam.

  
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Sorarse
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Jan 26, 2009 18:19 |  #4

I've used an old Tamron 500mm catadioptric lens on my 40D. Have had some moderate success with photos of the moon, but ultimately the size of the resulting image is somewhat smaller than what can be obtained using a scope.

Haven't tried any general sky shots or used it for multiple exposures for stacking, so can't comment on how useful it would be for that type of photography.


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SteveInNZ
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Jan 27, 2009 03:02 as a reply to  @ Sorarse's post |  #5

I have a Meade 1000mm f/10 mirror lens that must be pushing 20 years old now.
I can't say that I've found a great deal of use for it other than Sun/Moon related but then, I'm only just getting back into photography.
My main reason for keeping it is for photographing the solar eclipse in July.
Although, I've been wondering if I should sell it and buy something like an 80ED. The weight is about the same (2.4kg for this) and I expect that the optical quality of the ED would make up for the difference in focal length.

I haven't used it for astrophotography. I have an 8" SCT on a driven mount and can piggy back shorter f.l. lenses on that. The 1000mm doesn't seem to be the better option for any situation I can think of. OTOH, I do keep an eyepiece and bits in the box so that I can use it as a telescope.

Steve.


"Treat every photon with respect" - David Malin.

  
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Adrena1in
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Jan 30, 2009 07:05 as a reply to  @ SteveInNZ's post |  #6

Cheers all, I've certainly not heard anything particularly good about these mirror lenses, so I've decided to get a 66mm APO. Fingers crossed I'll be able to get hold of it before the Sword of Orion challenge is over! ;)


Canon EOS 450D, Sigma 18-200mm, Canon 50mm f/2.5 Macro, 2x TC, Revelation 12" f/5 Dobsonian, Mintron PD2285-EX webcam.

  
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High FL mirror lenses.
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