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Post by chrisc on Nov 19, 2011 2:18:44 GMT
f/stop, time etc...anyone ever done this with any decent success?
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Post by Steaphany on Nov 19, 2011 6:52:07 GMT
Back in the 1970's, I often did star trails and they were easy with film. Focus on infinity, depending on the light pollution level, it would be best to not have the aperture wide open. Set up the camera on a tripod, aim at a region of the sky and open the shutter for several hours. The length of the trail is based on the stars sweeping 15º across the sky every hour. The only problem I ran into was dew accumulating on the lens after several hours ruining any further exposure.
I haven't yet attempted to play with star trails using digital, though I have several software tools which would allow merging a succession of exposures.
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Post by Stevewebb on Nov 19, 2011 7:23:55 GMT
That would be a question for Yan Zhang at the other place. He is the master of it, I love his stuff. I have always fancied a go at it myself but never managed to get the opportunity to present itself at the right time. Whenever I have the time, it's cloudy
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Post by DonS on Nov 19, 2011 12:16:28 GMT
That would be a question for Yan Zhang at the other place. He is the master of it, I love his stuff. ( Agree!!!! His works are good... Is it okay if we open the shutter for several hours???
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Post by Steaphany on Nov 19, 2011 13:32:06 GMT
Is it okay if we open the shutter for several hours??? The problem I've seen with modern cameras is their maximum shutter tends to be limited, for example my Sigma SD14 dSLR and SA9 fSLR will close the shutter after no more than 30 seconds. The advantage of a fully manual film camera is often they have T timed exposure setting or a B bulb setting that will remain open as long as you need. ( a 4 to 6 hours exposure will be fine ) Remember, for a star trail image, you'll be exposing to a scene of darkness with low intensity point light sources.
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Post by chrisc on Nov 19, 2011 13:50:36 GMT
I found several tutorials which suggested a time of 1.5 hours in 30 second increments. I think, in large, this is because their cameras will not shoot longer than 30 seconds at a time.
However, I can do a mirror up lock on the D7000 and shoot until my battery drains, or set it up for an AC feed and shoot until I fall asleep. To beat the condensation, when I actually do my shot (moon needs to set first), I have a oil type space heater I will place close enough to the camera to avod a condesnation problem, but not so close to cause any unnecessary heat buildup.
The idea of stacking 180 30 second exposures seems a tad excessive and not particularly good as per utilizing all the merits of a single exposure in post production.
I plan on shooting at f/11 @ ISO 400 for 3, 30 minute exposures. Any thoughts on this plan?
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Post by Stevewebb on Nov 19, 2011 14:03:14 GMT
One thing you will have to do is make sure that the long exposure noise reduction is switched off, otherwise you will lose 30 mins while it takes a dark exposure and light trails will be interrupted.
From the research I have done on it, The general consensus among astro togs is that 30 second exposures are the way to go. There are a couple of quite good free programs that you can use to stack the images.
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Post by Barry on Nov 19, 2011 14:17:25 GMT
This was a 20 minute exposure with my Nikon D200, f2.8 and 100 ISO.
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Post by Steaphany on Nov 19, 2011 14:54:40 GMT
Barry,
That is a nice capture of Ursa Major !
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Post by Stevewebb on Nov 19, 2011 14:57:56 GMT
How on Earth can you tell what constellations are in there?
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Post by Steaphany on Nov 19, 2011 15:08:36 GMT
One thing you will have to do is make sure that the long exposure noise reduction is switched off, otherwise you will lose 30 mins while it takes a dark exposure and light trails will be interrupted. That is a design flaw of my Sigma SD14, there is no way to instruct the camera not to shoot a dark. Here is a question for the photographers with film experience, what is a model of fully manual 35mm camera that allows multiple exposures without advancing the film ? My Sigma SA9 can shoot multiple exposures, but is limited to the same 30 second exposure. The Pentax K1000, a main stay of 35mm film photographers and I used one a while back, can't and I need a camera which will allow me to pre-expose frames while also allowing multi-hour exposures.
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Post by chrisc on Nov 19, 2011 15:19:51 GMT
The reality is, that any camera can be made to reshoot the same frame over and over. All you need to do is load the film, pull back on the rewind until it is sufficently taut, then make a mark on the rewind knob at full stop point. Then advance the shutter and make a second mark where that frame ends. For the next exposure, hold in the rewind button on the bottom of the camera and rewind back to the original mark. Recock the shutter and shoot another frame. Repeat as necessary.
However, if you want to avoid all that nonsense, buy a Vivitar V3800N body and use your Pentax lenses instead of the cheesey ones they provide. The Vivitar has a button on the front of the camera that allows you to recock the shutter without advancing the film.
I think the body costs about $100 at B&H, though suspect you can find a decent used on on ebay or KEH.
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Post by chrisc on Nov 19, 2011 15:21:10 GMT
This was a 20 minute exposure with my Nikon D200, f2.8 and 100 ISO. What time of the night was that exposure made?
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Post by Barry on Nov 19, 2011 15:40:13 GMT
What time of the night was that exposure made? Just checked the exif information. 21/10/2008 at 20.15 But was that at the start or the end of the exposure The orange glow in the background was Brecon as this shot was taken up in the mountains away from any roads.
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Post by robmarshall on Nov 19, 2011 15:43:02 GMT
I haven't yet attempted to play with star trails using digital, though I have several software tools which would allow merging a succession of exposures. Do you mean time lapse (a series of closely taken shots) but instead of run as a video they are merged into one?
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