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 Post subject: Telescopes on DSLRS
PostPosted: Sat May 16, 2009 11:01 pm 
if a telescope is mounted on a dslr with live view and built in image stabilization, will the stabilization work effectively to prevent the huge wobbling of the telescope?

or will it work somewhat?

or will it have no effect at all cause of the huge wobbling?


Last edited by Photo Addiction on Sat May 16, 2009 11:42 pm, edited 2 times in total.

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 Post subject:
PostPosted: Sat May 16, 2009 11:07 pm 
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Image stabilisation only works on correcting the movement of the camera and lens, not any movement of the subject.

To be effective, the camera needs to know the focal length of the lens attached. Telescopes are manual so there is no way for the scope to tell the camera what focal length is.

Therefore you need some way to do that. I remember the Olympus E510 allowed you to manually enter a focal length, which it would then use to correct. The Sony A350 has no such option.

I have heard of people using "chipped" adapters to provide such communication with the body. These are adapters which include the electrical contacts and a chip programmed with some info.

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 Post subject:
PostPosted: Sat May 16, 2009 11:13 pm 
its not really the subject thats moving though...for example, in gordon's astrophotography video, you can see that jupiter is wobbling quite a lot (its not moving itself though, its the telescope thats unstable and making it wobble)

does the e520 have the same option of manually entering the focal length as the e510 or did they remove it?

and how effective is it?


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 Post subject:
PostPosted: Sat May 16, 2009 11:36 pm 
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Ok, when you mentioned the subject wobbling I took that literally, as opposed to the subject appearing to wobble due to camera motion.

I don't know if the E520 has the option too as I haven't used one, but I would guess they would leave such a feature in place. I never tried it with a scope so I don't know if it will help or not. I'd guess it might be more difficult than regular lenses so even if it does work, it might not be so effective.

In general you can manage the usage of the scope to minimise the impact of vibration.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Sat May 16, 2009 11:48 pm 
yeah, sorry about that...made it more clear in my first post

i think ive read somewhere (or maybe not) that theres a certain limit till the built in stabilization will work effectively (maybe on longer lenses or telescopes)...is this true?

so in the end, taking an image with self timer or cable release will give better results? and what about shutter speeds...is there a minimum?


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 Post subject:
PostPosted: Sun May 17, 2009 12:01 am 
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There will no doubt be a limit to the effectiveness of any stabilisation, but I don't know how much.

When I use my scope, I use a cable release and take single shots with a short pause between each one. Even the mirror movement can be enough to introduce vibration. Shutter speeds will be varied to suit the subject, and generally it would not be practical to be set fast enough to use that to get around motion blur.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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 Post subject:
PostPosted: Sun May 17, 2009 12:21 am 
thanks a lot for your help...learned some new things :P


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 Post subject:
PostPosted: Sun May 17, 2009 10:06 pm 
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Further to popo's comments, the greater the magnification, the more the potential wobble, and the harder an anti-shake system will have to work.

Cameras with built-in stabilisation can only shift their sensors by a certain maximum amount, and once the wobble exceeds that, then they become less effective. As you saw on my video, the targets were wobbling across half the frame or more, which is sadly way beyond the capabilities of an in-body anti-shake system.

The other things to remember are that subjects like stars and planets appear to be moving at high magnification due to the Earth's rotation, so I'm not sure what that - or tracking mounts - would do to an anti-shake system.

To be honest I've not tried mounting a Sony or Olympus body to a scope because I don't have the right adapter, but I suspect the anti-shake wouldn't be much help.


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 Post subject:
PostPosted: Sun May 17, 2009 11:22 pm 
thanks gordon, im kinda into astronomy...so before buying my first dslr, this is one of the things that im considering...

so far, ive established that live view is important...still undecided about stabilization :roll: but, theres still lots of time before im serious about buying a dslr


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 Post subject:
PostPosted: Tue May 26, 2009 2:48 pm 
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I do not want to scare you but if you want to do any AP (Astronomy Photography) more then planetary imaging, then you need to invest some serious $$$. I have been shopping around for the past few weeks in order to acquire such equipment.

Forget about IS body stabilization. This won't help you. A good mount, preferably a GEM mount is the best solution. If you have a Canon 450D or better, you can remotely control the camera with the EOS Utility or use DSLRFocus/DSLRshutter. The later are 2 freeware widely use amongs DSLR AP community.

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 Post subject:
PostPosted: Tue May 26, 2009 9:52 pm 
yes, i understand its not cheap...but ive seen some astrophotographers' photos taken with their normal dslrs for long exposures (10-12+ hours)...photos of milky way, for example

as far as i understand, only pictures of stars and galaxies can be made through this technique right?


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 Post subject:
PostPosted: Tue May 26, 2009 9:58 pm 
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Yes you need a motorized mount and a pc to autoguide/track the star to counter effect the earth rotation and whatever object you are shooting orbit.

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http://www.astronomyphotography.com


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 Post subject:
PostPosted: Tue May 26, 2009 10:27 pm 
true...

even a mount can be twice as costly as a scope :|


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