Night Sky PP Issues

[VprHis]

Greetings, all.

What we have here is a picture of the night sky that I took a couple days ago. It's something I'm trying to develop, and I've hit a bit of a wall.



Canon EOS 60D
Canon EF-S 18-55 IS @ 18mm
ISO 100
f/3.5
66 sec.

The main problem I'm having is in the post. I'm using Canon Digital Photo Pro, editing in RAW, and converting to .jpg. No matter what I do, however, I'm getting tons of noise/compression artifacts in the image. I'm a total novice when it comes to photo editing, so this is how I'm trying to improve

Some issues I've identified:
1. Camera simply doesn't have a great low-light sensor. Some 'hot' pixels.
2. Long exposure allows star movement to create blur--I'll sort this out empirically
3. I need a darker sky--I'm trying to dampen down a lot of city light, especially on the right.

Does anybody have suggestions on how to better adjust this either during capture or post?

Link to Original Image (Flickr)

Be brutal--it's the only way I'll learn.

Thanks in advance.


Fun fact: This is paired with a 'star trails' shot showing the big dipper revolving around Polaris. I got chased inside by a skunk before the exposure finished, though, so it's a paltry thing.

[SwissJon]

There's nothing wrong with the 60D's sensor. The problem you have is pollution I think.. The sky isn't completely dark because of light pollution reflecting of dust particles. You also get noise when you leave the sensor open for extended lengths of time. You could increase your ISO and reduce your exposure time, it's a trade off between noise caused by long exposures and noise from high iso. You'll have to experiment. That would also help with #2. You get longer star trails from shooting toward the equator than you do shooting toward the pole because the stars move faster.

If you're shooting in a city, where there's dust and pollution and lots of light, then fairly obviously you're not going to get as good a photo of the stars as you would on a mountain top where there's clear air and no light pollution. That's why they put observatories on tops of mountains, not in city centres. There's really not much that can be done in that case except suggest you take a holiday somewhere high up and dark!

As a general rule with night photos with stars, unless you're shooting with a high powered lens and looking to photograph constellations or planets, you'd be well advised to include something else in your photo to give it context.. A derelict building, an old church, a dead tree.. Otherwise, at 18mm like you shot at, you end up with a load of White spots on a dark background and it's impossible to tell if you're photographing stars or spilled sugar on a black sheet of paper. Remember to compose the photo properly, the subject will be whatever you put in the foreground, even if you're trying to show the stars..

[sk66]

Even at 18mm 66sec is enough to get blurring/trails; if intentional, they should be quite notable. For trails it is usually necessary to combine many images with shorter trails to get long trails...especially with a polluted sky.

For sharp stars/dark sky in your situation try stacking a single image with black sky (underexposed) in an "additive mode". When you add nothing to nothing (black to black) you get nothing...when you add a little to a little (underexposed star) you get more.

[VprHis]

Thanks, gents,

Appreciate the feedback. I'll see if I can knock this out next time I've got a clear sky.

...I think I can avoid the pollution if I just set up by the lake shore. The sky's much, much darker there. That should make life much simpler.

[tlpphoto]

If it helps any, the star trails you see in the bottom two pictures of this blog post:
Radiant View Photography Photo Blog: Saguaros, Sunrises and Star Trails
were made using 10 and 15 four-minute exposures -- a total of 40 minutes for the 2nd to last image and 60 minutes for the bottom image. You can see that each star, especially those near the north star, really doesn't move that far.

To combine the images in PS, just load them all into one file, then change the blending mode to "lighten." Shoot in RAW (which the 60D should support) and try different white balance settings in post processing. I think I used "tungsten" but I'm not sure now.

Tim