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06-21-2011, 07:29 PM   #1
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Silly Question? - input length for mirror?

Ok, perhaps a very silly question but what length do you input in manual mode for a 500mm Mirror lens? Thanks.

06-21-2011, 07:30 PM   #2
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The answer: 500mm. Always use the lens' (or mirror's) actual focal length. Reflections don't make it longer!
06-21-2011, 07:33 PM   #3
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QuoteOriginally posted by RioRico Quote
The answer: 500mm. Always use the lens' (or mirror's) actual focal length. Reflections don't make it longer!
Thanks, thought it might be shorter because of the doubling effect of the mirror arrangement.
06-21-2011, 07:35 PM   #4
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Nope, SR doesn't care about the physical size or weight or mass or whatever of anything, just its focal length. That fooled me too a couple years ago, before I wrapped my head around the concept.

06-21-2011, 07:36 PM   #5
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QuoteOriginally posted by RioRico Quote
Nope, SR doesn't care about the physical size or weight or mass or whatever of anything, just its focal length. That fooled me too a couple years ago, before I wrapped my head around the concept.
Appreciate it. Just started playing with the 500mm mirror lens that my children gave me. Thanks again.
06-21-2011, 07:39 PM   #6
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I own one of these. They are fun to use. Enjoy using it!!
06-21-2011, 07:40 PM   #7
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QuoteOriginally posted by stevbike Quote
I own one of these. They are fun to use. Enjoy using it!!
Thanks, mine came with a 2x and I've had it out once so far just to see what it could do. I'd like to try some moon shots with it. Have you done any astrophotography with yours?
06-21-2011, 09:45 PM   #8
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QuoteOriginally posted by Docrwm Quote
Thanks, mine came with a 2x and I've had it out once so far just to see what it could do. I'd like to try some moon shots with it. Have you done any astrophotography with yours?
Note that a 2x teleconverter will double your FL, so you should enter 1000mm when you're using it.

06-22-2011, 05:30 AM   #9
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QuoteOriginally posted by Docrwm Quote
Thanks, mine came with a 2x and I've had it out once so far just to see what it could do. I'd like to try some moon shots with it. Have you done any astrophotography with yours?
Yes I too have a 2x converter and have done some moon pictures. They came out ok but not excellent. Still nice images to look at though. With a bit of cropping you get full frame images of the moon that look nice. I only wish that they where a bit sharper.

Here is a upload of the "super Moon" I posted on the weather network. http://www.theweathernetwork.com/your_weather/details/620/4133173/140/upload/0/2155505/uid/

Last edited by stevbike; 06-22-2011 at 05:47 AM.
06-22-2011, 05:35 AM   #10
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QuoteOriginally posted by m42man Quote
Note that a 2x teleconverter will double your FL, so you should enter 1000mm when you're using it.
At least on the K-m, when using manuallly set lenses, the maxium length lens that can be set is 800mm.
06-22-2011, 05:59 AM   #11
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QuoteOriginally posted by stevbike Quote
At least on the K-m, when using manuallly set lenses, the maxium length lens that can be set is 800mm.
Thanks guys. Yes, on the K-x the maximum manual lens setting is also 800mm.
06-22-2011, 11:36 AM   #12
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QuoteOriginally posted by Docrwm Quote
Thanks guys. Yes, on the K-x the maximum manual lens setting is also 800mm.
So if you use a 500mm and 2x TC, just enter 800mm anyway. That's close enough. Then put the rig on a tripod and switch-off SR, because 800-1000-1200mm is just about impossible to deal with handheld! My Rubinar Makpo 1000/10 mirror (1760g) *can* be handheld on a bright day, but it's not much fun. Tripod, sandbags, whatever it takes to stabilize it, whew!

I haven't bothered putting the much smaller 500/8 on a 2x TC because 1) CIF doesn't work at f/16 and 2) I get better IQ with cropping than with a TC. Also note that LONG lenses aren't good for distance shots in warm / murky atmosphere -- air roils, particulates diffract, images are pale and fuzzy, etc. I mostly use my 500/8 for people-shooting in urban settings, with subjects usually less than 100ft away.
06-22-2011, 01:15 PM   #13
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QuoteOriginally posted by RioRico Quote
So if you use a 500mm and 2x TC, just enter 800mm anyway. That's close enough. Then put the rig on a tripod and switch-off SR, because 800-1000-1200mm is just about impossible to deal with handheld! My Rubinar Makpo 1000/10 mirror (1760g) *can* be handheld on a bright day, but it's not much fun. Tripod, sandbags, whatever it takes to stabilize it, whew!

I haven't bothered putting the much smaller 500/8 on a 2x TC because 1) CIF doesn't work at f/16 and 2) I get better IQ with cropping than with a TC. Also note that LONG lenses aren't good for distance shots in warm / murky atmosphere -- air roils, particulates diffract, images are pale and fuzzy, etc. I mostly use my 500/8 for people-shooting in urban settings, with subjects usually less than 100ft away.
The few I have tried at a distance look like old surveillance photos. The 2x makes everything very dark and hazy even in the daylight shots I tried on the one clear day since I received it.
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