Posted by Brian Jackson on October 22, 2009 at 10:47 PM
I've seen a few Milky Way photo's this summer and several questions of how to do this so I thought I would give it a try as I use to be into astronomy. All though this picture isn't really to great it's just to show what you can pick up in a bad location. I was between Denver and Colorado Springs and noticed the skies really clear one night so I pulled over and snapped a few shots. This was a really bad location as the center of the Milky Way is pretty much south and a little east. Basically right over Colorado Springs. Really bad light pollution. I had to really bring down the exposure in photoshop to get rid of all the light.
This is 5 - 50 sec shots at 2.8 and ISO 3200 at 14mm. Most people will say you can only shoot for around 20 - 30 seconds which is true if you are point up in the sky, but you can get by with more if you are pointing right off the horizon. Also it's much better to take 10 one mins exposure then 1 10 min exposure. All has to deal with single to noise ratio. Do to the fact that I really wasn't planning this I forgot to take my dark frame, so you will see lots of extra pixels that are created from the sensor heat. I took this about 3 -4 weeks ago. Just now looking at it.
What you want to do is take 5 - 10, 30 - 45 second shots and then when you are done take 1 - 2 shots at the exact same setting except with the lens cap on. This will be your dark frame. In photoshop then take the shots and stack them and use the auto align feature. Once you have shot aligned then you can flatten the image and now bring in the dark frame. Again auto align. Change the dark frame layer blending to difference and it will remove all the hot pixels. The dark frame sometimes can get a little tricky.
This probably isn't the best time to post this as we are getting into winter, of which our night sky is now starting to point away from the center of the Milky Way, so not as much will be visible but I hope this helps for the future.
This is pretty much straight out of the camera except for turning the blacks way up (like 80-90) in camera raw to remove all the light pollution (or try to).
Posted by Bryan Maltais on October 22, 2009 at 10:51 PM
gonna have to bookmark this thread to remember the technique.
Posted by Jeremy Kessler on October 22, 2009 at 10:52 PM
Pretty incredible. Any chance you could post a 100 percent crop of an area? what camera did you use to take this?
Posted by John Mumaw on October 22, 2009 at 11:18 PM
Thanks, Brian.
Some interesting tips there.
I tried this last week with the only f2.8 lens I have...a 16mm fisheye lens.
Exposed for 30 sec. @ ISO 3200 and used the in-camera dark frame subtraction (so called 'noise reduction') on a pretty cold night in middle of nowhere Utah. I may have blown it by 'lighting' up the trees during the long exposure.
My question is why stack 5 images when just one will do? I can see the stacking of images when attempting a 'star trail' type of shot.
Is it so you can get the intensity that I see here? Or is that light pollution?
Regardless, I really appreciate the time and effort you spent to put this together!
I'll post mine now, although resizing down seems to really cause a loss of stars.
Posted by John Mumaw on October 22, 2009 at 11:26 PM
My example. Wish I could have achieved the color and depth of yours.
Posted by Brian Jackson on October 23, 2009 at 12:17 AM
Jeremy, here's your 100% crop. And it was the D300, Nikon 14-24 lens.
Posted by Brian Jackson on October 23, 2009 at 12:32 AM
John, I'll let you read about the stacking below. But the basics are you want more signal (light) and less noise. When you take a 10 min exposure your signal is increasing linearly (good), but the noise goes up as the square root of the exposure (bad). So by stacking you can bring out more signal and less noise.
If I had really planned to do this I would probably take 20 - 30, 30-45 sec exposures at a lower ISO like around 1600, to help with the noise. I'd try to find a place in like South Park Colorado or somewhere in New Mexico or Arizona to get away for any light pollution. You can still pick up major light pollution over 100 miles away on a long exposure. Also all my shots I had NR on as well, on normal. But taking the dark frame will still help out on some of the pixel noise.
As for your shot, yes taking more shots and stacking them will defiantly bring out more color, but to be honest I bet you have more color in there. I'd check your WB as I looks really blue. Try changing the WB and see if there is not more color in there that you are not seeing.
Here's also straight out of the camera, one image. The colors from above are not from light pollution. Actually if I had taken this out in a dark sky, the colors would pop a lot more. But since I had to move the black slider so far up in camera raw, to remove the light pollution, I lost lots of color. Basically Colorado Springs would be in the bottom right corner. I'm shooting just above the horizon.
Posted by John Mumaw on October 23, 2009 at 6:54 AM
Thanks, Brian!
Posted by Brian Jackson on October 23, 2009 at 2:00 PM
Discussion
11 repliesThis is 5 - 50 sec shots at 2.8 and ISO 3200 at 14mm. Most people will say you can only shoot for around 20 - 30 seconds which is true if you are point up in the sky, but you can get by with more if you are pointing right off the horizon. Also it's much better to take 10 one mins exposure then 1 10 min exposure. All has to deal with single to noise ratio. Do to the fact that I really wasn't planning this I forgot to take my dark frame, so you will see lots of extra pixels that are created from the sensor heat. I took this about 3 -4 weeks ago. Just now looking at it.
What you want to do is take 5 - 10, 30 - 45 second shots and then when you are done take 1 - 2 shots at the exact same setting except with the lens cap on. This will be your dark frame. In photoshop then take the shots and stack them and use the auto align feature. Once you have shot aligned then you can flatten the image and now bring in the dark frame. Again auto align. Change the dark frame layer blending to difference and it will remove all the hot pixels. The dark frame sometimes can get a little tricky.
This probably isn't the best time to post this as we are getting into winter, of which our night sky is now starting to point away from the center of the Milky Way, so not as much will be visible but I hope this helps for the future.
This is pretty much straight out of the camera except for turning the blacks way up (like 80-90) in camera raw to remove all the light pollution (or try to).
Some interesting tips there.
I tried this last week with the only f2.8 lens I have...a 16mm fisheye lens.
Exposed for 30 sec. @ ISO 3200 and used the in-camera dark frame subtraction (so called 'noise reduction') on a pretty cold night in middle of nowhere Utah. I may have blown it by 'lighting' up the trees during the long exposure.
My question is why stack 5 images when just one will do? I can see the stacking of images when attempting a 'star trail' type of shot.
Is it so you can get the intensity that I see here? Or is that light pollution?
Regardless, I really appreciate the time and effort you spent to put this together!
I'll post mine now, although resizing down seems to really cause a loss of stars.
If I had really planned to do this I would probably take 20 - 30, 30-45 sec exposures at a lower ISO like around 1600, to help with the noise. I'd try to find a place in like South Park Colorado or somewhere in New Mexico or Arizona to get away for any light pollution. You can still pick up major light pollution over 100 miles away on a long exposure. Also all my shots I had NR on as well, on normal. But taking the dark frame will still help out on some of the pixel noise.
As for your shot, yes taking more shots and stacking them will defiantly bring out more color, but to be honest I bet you have more color in there. I'd check your WB as I looks really blue. Try changing the WB and see if there is not more color in there that you are not seeing.
In Depth Signal to Noise
http://www.astropix.com/HTML/I_ASTROP/SIGNAL.HTM
Here's also straight out of the camera, one image. The colors from above are not from light pollution. Actually if I had taken this out in a dark sky, the colors would pop a lot more. But since I had to move the black slider so far up in camera raw, to remove the light pollution, I lost lots of color. Basically Colorado Springs would be in the bottom right corner. I'm shooting just above the horizon.