Help with star trails?

[CaP17A]

I've been trying to do star trails for the past couple of nights. Hasn't been working so well. First night I shot with a Tamron 18-270, 100 ISO, and f/22 (this was foolishly before I read how to create star trails). It came out almost black at a 60 minute exposure. Kinda cloudy night so I blamed it on that. Now I know that the stars wouldn't even show up so obviously learned from that. Next night, after reading tutorials, I shot with a 50mm f/1.8, 100 ISO, and f/3.5. This came out over exposed, and it looked like a normal day shot and the sky was completely white (80 minute exposure). Tonight since it is pretty clear out, I'm going for a 60 minute exposure. My question is should I keep the prime lens on which lets in tons of light, or just go with the kit 18-55 at around f/4? I think the second option would be better because the low aperture shows the stars while the extra glass lets a little less light in. I wish I had some filters to toss on the lenses

[KirkS518]

I think you'd be better off asking this in the celestial section.

I'm not super-fluent in star trail imaging with digital (did it on film), but I think you need to use shorter exposure times, (30 seconds seems to be the typical used) and then stack the images in PP. With those incredibly long exposures, your getting tons of noise, which may be what's rendering as black in the final. Also, longer focal lengths will increase the effect of the startrails, whereas wider focal lengths seem to minimize the effect from what I have seen and understand (it's a perspective thing I think).

There are a few free star trail programs out there for stacking and stitching. Google will be you friend there.

[CaP17A]

Originally Posted by KirkS518

I think you'd be better off asking this in the celestial section.

I'm not super-fluent in star trail imaging with digital (did it on film), but I think you need to use shorter exposure times, (30 seconds seems to be the typical used) and then stack the images in PP. With those incredibly long exposures, your getting tons of noise, which may be what's rendering as black in the final. Also, longer focal lengths will increase the effect of the startrails, whereas wider focal lengths seem to minimize the effect from what I have seen and understand (it's a perspective thing I think).

There are a few free star trail programs out there for stacking and stitching. Google will be you friend there.

I read about that but the problem seems to be that my T2i doesn't write the image onto the class 6 card i have fast enough so there will be gaps.

[mrbubbles]

Cap what do you mean the T2i doesn't write fast enough? It definitely can. Writing 30 second shots to the card takes no longer than writing a 1/500th second shot. Its still just one picture.

I use my T1i with various SD cards of different speeds and have never ever had a problem.
This was about 75 30 second shots...no gaps.

Startrails2 by bjacobsen311, on Flickr

[fnothaft]

Originally Posted by CaP17A

I've been trying to do star trails for the past couple of nights. Hasn't been working so well. First night I shot with a Tamron 18-270, 100 ISO, and f/22 (this was foolishly before I read how to create star trails). It came out almost black at a 60 minute exposure. Kinda cloudy night so I blamed it on that. Now I know that the stars wouldn't even show up so obviously learned from that. Next night, after reading tutorials, I shot with a 50mm f/1.8, 100 ISO, and f/3.5. This came out over exposed, and it looked like a normal day shot and the sky was completely white (80 minute exposure). Tonight since it is pretty clear out, I'm going for a 60 minute exposure. My question is should I keep the prime lens on which lets in tons of light, or just go with the kit 18-55 at around f/4? I think the second option would be better because the low aperture shows the stars while the extra glass lets a little less light in. I wish I had some filters to toss on the lenses

How are you deciding how long to expose for? It seems like you're somewhat grasping at straws with exposure problems. The exposure parameters you need will vary significantly depending on light pollution, ambient lighting, etc.

What I've normally done when shooting star trails is to take a few shots at my widest aperture and at the highest ISO I have. I use this to get a baseline for what exposure I need to get the sky correct — I suggest to overexpose the sky and then bring down by 1 stop.

After getting this exposure, I then stop down a bit and also bring the ISO down until I get to an exposure length I'm looking for.

[CaP17A]

Originally Posted by mrbubbles

Cap what do you mean the T2i doesn't write fast enough? It definitely can. Writing 30 second shots to the card takes no longer than writing a 1/500th second shot. Its still just one picture.

I use my T1i with various SD cards of different speeds and have never ever had a problem.
This was about 75 30 second shots...no gaps.

That is a really great picture! I thought that 30 seconds per picture to write to the card would create gaps, apparently it didn't though. Foolish me haha! There it is right there. I don't know what I was thinking :P


Front Of House Star Trail by CaP17A, on Flickr

[CaP17A]

Originally Posted by fnothaft

How are you deciding how long to expose for? It seems like you're somewhat grasping at straws with exposure problems. The exposure parameters you need will vary significantly depending on light pollution, ambient lighting, etc.

What I've normally done when shooting star trails is to take a few shots at my widest aperture and at the highest ISO I have. I use this to get a baseline for what exposure I need to get the sky correct — I suggest to overexpose the sky and then bring down by 1 stop.

After getting this exposure, I then stop down a bit and also bring the ISO down until I get to an exposure length I'm looking for.

What I did is set to what settings would be ideal (generally f/3.5, 30", 200-400 ISO), then I double the ISO and half the time, then do it again, just to see what it would look like. I'm done with trying the single long exposure haha...don't know why I thought it would work.

[Caspita]

How are you guys putting this together in photoshop.....just a whole bunch of layer masks?

[CaP17A]

Originally Posted by Caspita

How are you guys putting this together in photoshop.....just a whole bunch of layer masks?

There is a plugin i believe. I don't use photoshop, I use StarStax, an application for both mac and windows but i believe that startrail.exe (something like that) is better but is only for windows.

[armis]

Originally Posted by CaP17A

That is a really great picture! I thought that 30 seconds per picture to write to the card would create gaps, apparently it didn't though. Foolish me haha! There it is right there. I don't know what I was thinking :P

FYI, it only takes 30 seconds per shot because you have long exposure noise reduction enabled. You could always disable it and substract a dark frame yourself (whatever software you're using, it probably has the option somewhere to included a dark frame).

[howesit]

I had never heard of stacking before I came here to this forum, so all of mine are just straight off the camera. this one is just less than 45 minutes. iso 100 f/stop 3.5

[fazlu]

i'm gonna do a startrail this weekend , would surely go for stacking in photoshop rather then doing it in first attempt