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Actually they are trailed a bit if you look carefully, especially at the edges. You minimize it by shooting wide, and short exposures. Even at 1 minute I got some trailing as you can see. 30 seconds would have been better, but it presents other problems as well.
Try setting WB to tungsten if you're interesting in getting rid of the yellow cast which is caused by light pollution.
Thanks for the suggestion - will try that. I know I should set a custom WB, but for all of my deep-space astrophotography (http://www.flickr.com/photos/fuzzsummit/sets/72157624473380810/ - broken link) so far I haven't really bothered with WB because I've been too busy trying to get good data in the first place (e.g. focus, tracking, number of subs). For wide-field shots like of the Milky Way (especially with light pollution) it makes a bigger difference. Since I have the raw files, maybe I'll go back and play around with the WB and see what I can get.
Actually they are trailed a bit if you look carefully, especially at the edges. You minimize it by shooting wide, and short exposures. Even at 1 minute I got some trailing as you can see. 30 seconds would have been better, but it presents other problems as well.
Your eyes are a lot better than mine.. I see maybe 1-2 out of all the photo's I figured you where using a star tracker or telescope..excellent photo
Excellent shots kdog! I have few technical questions for you since I enjoy taking these types of shots as well:
* What were you settings (ISO, secs, f-stop)?
* Did you use Canon's builtin long exposure noise reduction (dark frame)?
* Are these all single frames or did you do some stacking?
* How about post process NR software?
* Where were they taken?
Here are few of my latest shots while visiting Mt. Rainier. There were a lof of shooting stars. However I didn't capture any in the frames. I was focused more on the Milky Way and Rainier:
Image Info: 5D2, 30 sec, f4, 17mm, ISO 4000, Single frames, no long exposure NR used, 8/11/2010 ~10:30PM.
Derek
Last edited by MtnSurfer; 08-19-2010 at 12:53 PM..
Howdy, Derek. Great shots! Did you camp out on Rainier? Looks like a great place to shoot.
Exposure data for mine is F2.8, ISO1600, 60 secs. No noise reduction at all, neither in-camera, nor in post, save for whatever the default is in ACR. They look good at small sizes, but if you zoom in, you can see the noise. Correct me if I'm wrong, but one cannot use the in-camera long exposure NR when taking continuous shots because you'll have huge gaps due to the time it takes to do the NR. Now, I did notice there is also in-camera high ISO NR, but I didn't know if it had the same problem with long-exposure NR, so I turned it off as well. I didn't want anything slowing down the process. They're all single-frame, no stacking. If I do the arithmetic, it looks like your setting would have allowed for more than twice as much light as mine. Next time I'll increase my ISO and decrease my shutter speed.
Speaking of stacking, I may as well add this one to the thread. You can actually see all the meteors if you look carefully. The long lines extending towards the lower right are airplanes.
Correct me if I'm wrong, but one cannot use the in-camera long exposure NR when taking continuous shots because you'll have huge gaps due to the time it takes to do the NR.
You are correct. With long-exposure NR turned on, the camera automatically takes another frame with the same exposure (but with the shutter closed), so a 1-min shot turns into 2 minutes total.
Using the in-camera NR is not really the way to go. There are two "imperfections" that show up in long-exposure frames: thermal signal and noise. Even though it's called noise reduction, LE NR really removes thermal signal. However, by doing a single-frame dark subtraction, it removes the thermal signal but adds the noise that is in that single dark frame.
That's why you want to take many separate dark frames, create an average master dark, and then subtract that master dark from your light. Because noise = square root of total signal. So the more darks you use to create the master dark, the higher your signal-to-noise ratio = lower noise in the master dark. So if you subtract a master dark created from 24 separate dark frames, you can remove the thermal signal without adding much noise.
This is also another reason you want to stack a lot of light frames for astrophotography since more frames = higher SNR = less noise in the light frames to begin with.
All of mine (in this and other threads) are with a stock unmodded 40D.
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