Star Trails

[Chainsaw_Willie]

Now THAT'S a useful tip. Thanks!

[NashBoarder]

For those with noise and other artifacts from the sensor, you might want to try taking a dark frame and subtracting it from the image. If you are taking a 30 minute exposure, also take a 30 minute exposure with the lens cap on. The only pixels that will be lit will be from the thermal energy of the sensor. You can subtract this in photoshop from your star pics to get rid of the noise.

Thanks!!!!!! I'll have to try this next time I'm taking a star trails photo.

[cmor]

I gave another one ago tonight, stacked exposures, didn't go so well. Lots of noise.

[Lonnie]

For those with noise and other artifacts from the sensor, you might want to try taking a dark frame and subtracting it from the image. If you are taking a 30 minute exposure, also take a 30 minute exposure with the lens cap on. The only pixels that will be lit will be from the thermal energy of the sensor. You can subtract this in photoshop from your star pics to get rid of the noise.

Sounds like cheating to me...

[Noonan]

Taken from a friends deck in Breckenridge.

The trees picked up a bit of light from the porch lights - tree on the left is looking a little red from beetle kill.

[bmg97]

^^^ Looks like snow !

[cascadianwarrior]

First attempt @ Priest Lake, ID a few weeks back. I didn't have a tripod with me so I had to just wing it and hope for the best. 45 minute shot, ISO 100, f5 @ 12 mm.

[cmor]

[Fuzz]

^^^ Very nice! I've been thinking about lighting up the foreground during wide-field astro shots as well, but just haven't gotten around to it.

[Wes Mantooth]

cmor that last one is awesome

This is my first attempt, I need a longer exposure but I only had time to try one

[cmor]

I opened it up a little more to f3.5 at iso 200 this time. I wish the foreground was a little better

[cmor]

The conditions finally lined up for a reflection attempt.

[JabbaTheHuck]

^^^Well done Cmor, I think that is one of your best.

[Fuzz]

cmor, how long of exposures for these? They look longer than 30 minutes.

[ak_powder_monkey]

I'll try mirror lockup, as for the sturdy tripod, well, for $20 you don't get much.

It was cloudy tonight, so I tried a shorter exposure at iso 3200, the nr reduction seemed to knock out most of the amp glow, im not sure why. I think a bit more pp might be able to bring this one out a bit.

This is BADASS!

[NashBoarder]

I opened it up a little more to f3.5 at iso 200 this time. I wish the foreground was a little better

Can you provide some info on length of exposure. Looks like it's pretty long (1 hour +). Also, I've had problem with noise from my sensor heating up on my 40D. Any tricks you are doing in post? What are you shooting with? Thanks in advance.

[cmor]

The circular one at the north star was 5 hours, the lake was 6 hours. Both are stacked 5 minute images. I'm using an a700 with a vivitar fisheye. A full frame would be nice to control noise on the longer exposures and give yourself more latitude on the exposure settings if you have the budget. Stacking images helps with the noise. Otherwise a dark frame subtraction seems to work quite well if its cold enough out. But if possible keep your lens warm to fend off condensation. Both of the last two are f3.5 iso200.

[Fuzz]

Thanks for the specs. I've been stacking, but for deep-space objects ([ame="http://www.tetongravity.com/forums/showpost.php?p=2517400&postcount=16"]latest attempt here[/ame]) rather than star trails.

[cmor]

Do you manually align? How do you pull that off with a static tripod? I didn't mention before but the big problem with noise is any NR pulls all the detail out of your stars.

[pointedem]

The conditions finally lined up for a reflection attempt.

[/IMG]

I bet you were kicking yourself for lighting up the forground.

[cmor]

I bet you were kicking yourself for lighting up the forground.

I lit it up intentionally. Since it's a stacked image you could easily take it away. But there's not that much reflection. Trying to shoot star trals off of water is challenging. Even when everything lines up. I think its possible to get a better reflection. But I haven't ever seen one. I thought the trails over lit up lake bottom would give more depth.

[Fuzz]

Do you manually align? How do you pull that off with a static tripod? I didn't mention before but the big problem with noise is any NR pulls all the detail out of your stars.

Those two shots are 5 frames at 30 seconds each (max I could do without a remote), at 32mm. At 30 seconds (and 32mm), there's very little trailing, so I don't need to track the sky. I've done up to 60 seconds (at 18mm) with no guiding or trailing. For longer exposures, I do attach the camera to my telescope (either piggyback or prime focus) -- however, I have an alt-az mount, which is not the best for the accurate tracking required for serious astrophotography (can't afford the wedge to convert to equatorial just now).

Curious, what are you using to stack? I use DeepSkyStacker, but for the Andromeda close-up I tried Nebulosity, which gave much better definition than DSS.

Based on your examples, I'll have to experiment with stacking star trails.

[cmor]

Curious, what are you using to stack?

Photoshop. Usually using a lighten layer batch action.

[Fuzz]

Interesting thread on Cloudy Nights on ISO and noise: http://www.cloudynights.com/ubbthrea.../1#Post3352951

One of the posters, Jerry Lodriguss, is a well-known astrophotographer and has published several popular books on it.

[NashBoarder]

Do you have to do the dark frame on the same night as the star trail one or just under simliar temps?

Also, I guess I'd need something like this?
[ame="http://www.amazon.com/Control-Shutter-Digital-Cameras-compatible/dp/B0018205KE/ref=sr_1_3?ie=UTF8&s=electronics&qid=1253809975&sr =8-3"]http://www.amazon.com/Control-Shutter-Digital-Cameras-compatible/dp/B0018205KE/ref=sr_1_3?ie=UTF8&s=electronics&qid=1253809975&sr =8-3[/ame]

I currently just have a simple shutter release.

Thanks for the help.