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Author Topic: Astrophotography  (Read 2657 times)

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« on: May 27, 2008, 13:16 »
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As my previous thread had stated, I now have a 500mm f/4 lens (which is fantastic) and a 1.4x II extender.

I would like to do some astrophotography.  Is it possible with a focal length of 700mm? 

Does anyone have any experience using lenses to do this kind of thing vs. an actual telescope?

Just wondering if its possible? How to go about it?  I checked online and everyone is using these giant refractor things.

Thanks for any input,

JG


« Reply #1 on: May 27, 2008, 13:22 »
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Yes I guess this is possible, should work well on the moon if u dont have chromatic aberration with the conversion.
Sturdy tripod + use of the self timer to avoid blur

You should visit astro groups on Flickr there are amazing pics

L

« Reply #2 on: May 27, 2008, 14:48 »
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I've no experience with proper astrophotography, but I have occasionally tried photographing moon, and stars and planets through a telephoto.

One thing I guess will be essential, especially if you're using 700mm, would be a properly set up equatorial mount. In my limited experience, with exposures only as short as a few seconds the stars begin to streak. You've got to have a camera that follows them.

j2k

« Reply #3 on: May 27, 2008, 14:52 »
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As Bateleur said with such lens you are going to see blur due to Earth's rotation even on relatively short exposures. Without a tracking equatorial mount you might be limited to the moon.  You could maybe try to stack a bunch of short exposures to avoid star trails. 



Let us know how it goes :)

EDIT:
you might want to look up some information about barn door drive - it's a simple tracker that can be made with some spare wood and tools.  Can be motorized or not. 
I have this link in my bookmarks:  http://hometown.aol.com/Davetrott/page17.htm
I don't know if such setup would be feasible for a heavy 500mm lens thou.
« Last Edit: May 27, 2008, 15:03 by j2k »

« Reply #4 on: May 27, 2008, 14:59 »
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with a 700 mm I though more about moon shots, for which 1/200 s 1/125 s should be fine.
planets and stars and you will like said before need a equatorial mount  up to follow them and do pose of few seconds to few minutes.
Moon is a good place to start :)

« Reply #5 on: May 27, 2008, 16:16 »
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With the moon you'll be ok, short exposures.
For the planets you will need a lot more mm, say 2 to 4 meters to get any detail. For this sort of thing, you'd be better off with a webcam and a stacking program anyway....
I think most are using giant reflector things, in astrophotography, it's all about getting as much light as you can.
You can try your luck at the orion nebula though, get a lot of shots and stack them, you'll find out soon enough what your max shutterspeed/iso can be.





« Reply #6 on: May 27, 2008, 18:25 »
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There are sites of astronomy magazines such as Sky & Telescope that offer some guidance about astrophotography. 
http://www.skyandtelescope.com/howto/astrophotography/

I have the impression however that without a telescope you can not get much except moon shots and trailing stars. 

Regards,
Adelaide

« Reply #7 on: May 27, 2008, 18:49 »
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The general rule of thumb with night shooting is that stars will begin to show obvious blur after a 15s exposure. Aperture plays a huge role in determining how many stars will show - shooting wide open generally gives the best effect.

With 700mm the only thing you'll be able to shoot is the moon, which gets very boring very quickly. I've shot it using 900mm, and you have to anticipate its movement into the frame before pressing the shutter. At that magnification even slightly touching the camera results in severe shake.

... good luck!

« Reply #8 on: May 28, 2008, 11:13 »
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Thanks,

I appreciate all the input


« Reply #9 on: May 28, 2008, 11:37 »
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I set the timer between 3 and 10 sec exposure for the moon.  I also hold a black piece of soft cloth in front of the lens. Once the timer opens the shutter I quickly remove the cloth.  I put is back just before the shutter closes. This has helped me keep the blur and shake to an acceptable amount.  My moon shots still need a lot of work but they look really good at 8x10 or so.  This method is similar to the barn door method.  However in most cases its free or very cheap to do.  I've yet to get a moon shot that would even be close to being accepted at SS or IS.  I gave up really.

« Reply #10 on: May 28, 2008, 17:22 »
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I set the timer between 3 and 10 sec exposure for the moon.

Don't you get a big white blob?  My moon shots are taken with settings such as f/8 and 1/125s, in order to get detail on the moon's surface.

Recently in my trip I took some 15s exposures to get the moonlight over the mountains and rivers. Not very stockish, I think, but a good result for pleasure shots.

Regards,
Adelaide


 

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