Star Trails

My first real effort at this- exposures are aproximately 10min, 20min, and 30min.

 

Thats really cool

 

Thanks- I think I want to try it again with some things in the forground for perspective.

 

Nice work Jeff! I'm glad to see I'm not the only one around here who's been bitten by the star trail bug.

I have a suggestion for you if you want to try doing longer exposures. Moose Peterson has a good article on Star Trails here where he talks about the problem with doing star trails on a digital camera is noise. You can't go out and do a 4hr exposure like you could on film because the sensor will create a lot of noise in an exposure that long. The solution is to take many shorter exposures and stack them to create one trail. If you have CS3, Russel Brown has a tutorial here where he shows how to stack the images using his "Dr Brown's Stack-A-Matic", which you can download as part of his Dr. Brown's Services found on his website here. Also, he shows how to make a little movie of the stars moving across the sky. Since I don't have CS3, there is a free program called Startrails that I use to stack my star trails.

540 30s exposures (4.5hrs) stacked with Startrails


The thing I like about stacking shorter images is that not only does it reduce the noise in the photo, but it eliminates the sky glow from all of the street lights in my neighborhood, os I don't have to go find a nice dark spot in the country every time I want to try a star trail.

 

I like these. I tried them but mine were a disater because of the ambient light in my neighborhood.

 

Try the image stacking method. It allows you to take short exposures so you can eliminate the ambient light and still capture the movement of the stars. My neighborhood has lots of lights which would produce a lot of sky glow if I took longer exposures. As an example, the photo I posted earlier was taken in my backyard on a night with a full moon.

 

Thanks Craig. Make sure you read Moose's article as well. He gives a good background on how to do them.

The way I did that last one was to set the camera on manual, 30s and then choose the appeture that was correct for the 30s exposure. Then I set the camera to continuous fire and locked the cable release in the on position. If you look at the image, you'll notice gaps in the trails which shouldn't be there (they should be continuous). I learned the hard way that even shooting jpegs, the camera will only take so many in a row before it stops. The only way to get around that is to babysit the camera and keep restarting it every time it stops or to get Nikon's MC-36 Multi-Function Remote, which has a built in intervalometer.

 

Consider me on board with the merging trick. I didn't use any programs, just stacked 'em manually in Photoshop using... er, some blend mode. Look, I don't understand the many blend modes PS has. I just did a test combine and it looks like I used lighten. It was the coolest thing when I first learned about it, it gave me the hope that even in my terminally light polluted town I could still try star trail shooting.

The stack a matic script definitely makes it faster and easier though, the last time I did this I did it the hard way, copying and pasting one picture into the scene at a time. Bleh. Then setting the blend settings on each layer... Not cool. And I didn't have near as many layers as the examples in the stack a matic star trail video. I'll have to try this again to put the script to work.


I have several things to mention. First off, aperture doesn't work like you're used to for astro photography. I still don't fully understand this. Stars are generally considered point light sources, to the camera they're more or less one pixel wide. Point light sources seem to be effected less by changes in aperture. It's something like the ratio of the aperture to the focal length instead of just the aperture. The upshot of this being that if you're afflicted by light pollution, a narrower aperture will make reduce the light pollution more than it will the stars. Don't take my word for it, do a trial run and see. I don't use rules of thumb for this stuff, I take test shots and figure out what works.

I used that to let me get longer exposures for my trial run at a star trail shot a while back. The problem was that I was using a timer remote (intervalometer, whatever) but it seems to have a minimum wait time of 1 second between shots, and at 18mm (my widest focal length at the time) 1 second showed up as a visible gap between shots. So the longer the exposures the less noticable the gaps, or at least there were fewer of them. If I do it again with the ultra wide lens then 1 second might be affordable, or perhaps I CAN just set the remote to essentially hold the button down. I can do a thing where I push the button down and then slide a locking slider up, I never thought about it before but I suppose that WOULD let me just have it shoot as soon as the last shot is done if I have it set to burst mode.

I'm not even posting the test shot. I was happy with it, in the context of my badly light polluted skies, but it's still got bad light pollution glow and you can't see many stars.

Note #2: Beware the mist! I know that sounds like the tagline to a horror movie, but, well... here, check out this picture:
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I left my camera to shoot away for a while that night, while I went inside and watched TV. I went out to find my lens and camera covered in dew. And I can tell exactly how long it took to form because of the progression of images. Curiously enough it took almost exactly a half an hour to start forming.

I have no solutions to the dew yet. I have one wacky idea involving hitting the camera with an IR heat beam from an IR heating element, it's crude but I just need to keep the camera a wee bit above ambient temperature. Or else maybe just put a heater on it, maybe I could tack a simple low power heater onto it. They make them for amateur telescopes, I've never seen one but my assumption is that they don't really keep anything hot, just slightly above ambient temperature.

I just came back from a trip to the wilderness in Northern Minnesota, one of my big plans was to do a big production of star trail shooting. But I didn't do any. Yeah, I totally forgot to get my records for what sort of exposures worked for me, and I just can't judge the results based on the LCD screen preview image. Plus I didn't want to leave my camera out all night, for various reasons involving people stumbling around on the dark rocky terrain and possibly knocking the tripod over. Epic star trails require a very long cumulative exposure, and while I made sure I had the batteries to shoot it, in the end I just didn't like the idea of leaving the camera out and committed to shooting for that long a period of time in the darkness. Someone could have bumped into it when wandering around, the wind could have shifted and sent campfire smoke into the camera, that sort of thing.

So I went for trying not to blur the stars and just tried to get wide field shots of the skies in their full glory instead. It worked out pretty well.

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