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Focussing when photographing stars
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Hi All,
I was wondering if there is anyone out there who tinkers with Astrophotographer but just using a camera and lens and not a telescope.
I was wondering what technique you used to get the stars in focus.
From what I’ve read is could you go to infintity on your lens and then you go back a bit.
You can try to find a bright star and try to manually focus on it using Live View.
Are there alternative methods?
I know with a telescope you do other methods.The other question is how do you keep dew from lens on long exposures.
Is there any successful tactic?Kind Regards
Fergal
http://www.flickr.com/fergalocallaghanWe did a “Star” night with the camera club, and I was using infinity which worked
ok, the hardest part was getting a composition that was looked ok, ie something
in the foreground so that it wasnt just a picture of the sky and stars.To get the composition we bumped the ISO to its highest level, opened the aperture
to its widest and took a shot, if the composition was ok (disregarding the noise of course)
then closed the aperture down to f16 to f22, reduced the ISO to lowest and set the
shutter to about 20secs, if you do much longer you will get star trails. Cant say we had
any problem with condensation, just make sure you dont have the heat on in the car
before you get out into the cold night air and you should be fine.get a fast lens if you can and just focus on infinity…(thats pretty close to where those stars are :)) To keep fogging off your lens you can a) try “Rain-X” on a clear filter, or b) keep your camera warmer than the surrounding area somehow; e.g. use a filament-heated piece of glass in front of the lens, stick a chemical hand-warmer on the side of the lens (caution there, I tried that with my view camera in Antarctica to keep the groundglass warm (only worked so-so in that case) ), or use another gentle heat source.
” To keep fogging off your lens you can a) try “Rain-X” on a clear filter, or b) keep your camera warmer than the surrounding area somehow”
I would have thought quiet the opposite. I would have suggested allowing your lens to cool naturally (possibly in a plastic covering), so that it matched the surrounding temperature. Fogging is produced by cool air coming into contact with a warmer surface & the moisture gathers on the surface as is my understanding, but I could be wrong.If the camera becomes even slightly colder than the surrounding temp you will get condensation in any moderately humid environment.
Do the fridge test if you don’t believe me….:)Hi
There is an easy way to focus when shooting stars. Setting your lens to infinity does not quite work, you have to back it up a little bit, really trial and error and it just takes too much time. Next time you are out shooting stars try to cover your lens with white cloth (probably other colour will work as well but I’m not sure) set your lens to autofocus and try focus. Keep your shutter button half-pressed until your camera decides that there is nothing to focus on and stops the lens. And that’s really it. Now switch your lens to manual focus so it stays that way, do not touch focus ring and obviously take cloth of your lens. Shoot few frames and see for yourself.
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