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Old Feb 11, 2010, 9:48 AM   #1
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Default Stars at night HDR-very strange image

Here it is:
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Old Feb 11, 2010, 9:56 AM   #2
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looks like pins trying to poke through
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Old Feb 11, 2010, 4:45 PM   #3
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Now this looks crazy... can you tell us how you've created that one?
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Old Feb 11, 2010, 5:01 PM   #4
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Well, I remember some of it. I took 3 timed shots of the sstars and put them into PhotoMatix. Then I played within PSCS4 but I did so many things and erasures than I have no idea how this happened. It looks like embossed metal to me.
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Old Feb 11, 2010, 8:52 PM   #5
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Wow I thought thats exactly what it was .... embossed metal. But now its really interesting if its an HDR alteration from actual stars. Nice one. Really weird though.
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Old Feb 11, 2010, 11:38 PM   #6
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Definitely strange. What exposure settings did you use? And was there a light somewhere to the right? The strange effect seems to be stronger on that side, and it looks like there's additional light on that side of the frame.
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Old Feb 12, 2010, 12:06 AM   #7
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I was on bulb and did 20 sec,30 sec and about a min with a 12mmlens on the M8. f/8. Does that help?
There was no light on the right since it was about 1AM.
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Old Feb 12, 2010, 12:36 AM   #8
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The brighter area from the upper right diagonally to the lower center, looks about right for the Milky Way, depending on how your camera was oriented. I think that some of the effect may be from the alignment done by Photomatix. The rest may be from some noise reduction.
For these kinds of shots, you should do a dark frame subtraction to cancel out the hot pixels before putting them together. Just take a shot with the lens cap on for about the same exposure time as you are using. Quite a bit of what look like stars can turn out to be hot pixels on the camera sensot itself.

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Old Feb 12, 2010, 1:22 AM   #9
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thank you Brian. I will do that.
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Old Feb 12, 2010, 6:00 AM   #10
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Maybe Photomatix is creating a bit of a halo round each star which when combined gives you the effect you see.

Also, the Earth is rotating (360 degrees a day obviously) so on a 1-minute exposure the Earth has rotated a quarter of a degree. The sky will therefore rotate quarter of a degree around the pole star. If that's somewhere in the top left, those stars will have stayed relatively still and the bottom right will have moved more.

I think you can get tracking tripods to correct for that if you're doing a lot of long exposures at night.
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