Startrail photo, do you have tips or tricks?

[JEL]

I'm thinking about doing some startrail photos, and wanted to hear if anyone have any tips or tricks for that.

Especially whether it's better to go for 1 long exposure, or a series of shorter exposures which are then combined later.

Pros and cons of various methods.

Software recommendations, for this type of photography, would also be interesting.

Any info really.

Thanks
JEL

 

[agentgonzo]

Personally I tend to use a single long exposure rather than multiple short exposures just because I find it easier to do without the post processing, but YMMV. I've done a few.

Pros of the single exposure are that it's easier and you don't have to worry about taking multiple photos, stacking them in photoshop afterwards and making sure that each exposure is with the same settings/white balance etc. The only con that I can think of is that not all cameras can lock the shutter open for hours at a time.

Some advice that I'd give would be:
Use external power wherever possible. I've done a few with a fully charged battery and it stopped about 90 minutes into the exposure due to a low battery. The batteries also drop their voltage (run out) quicker when they are cold so you'll get less life from a cold battery (outside at night) than you will from a warm one, so beware of this.

Do a couple of 30s tests beforehand to make sure that the exposure and foreground is correctly lit. I've done a few before (like the one below) where I took about 15 test photos to correctly expose the foreground. As an example, the photo below, I used the flash at the start of the exposure and then turned the outside light on for 15 seconds to illuminate the tree (Silver clusterleaf - Terminalia sericea) before it all went black and just the starlight was present.

Use the widest angle lens you can.

If possible, try to get the camera pointed towards one of the celestial poles so that you get concentric trails. It looks prettier - but also follow the photography [ame="http://en.wikipedia.org/wiki/Rule_of_thirds"]rule of thirds[/ame] to create a more aesthetically pleasing photo.

I think that's all I have for the moment.

The trails come out better in the full res photo:

 

[Ripley]

Why don't you tell us what your setup is made of?
Camera? DX or FF?
Lens(es)?
Accessories?

If you (or your camera) have an "intervallometer" (timer, or similar) you can set it up to make a 30secs exposure every 40secs or so, around 90 shots per hour.
Many shorter shots are better than a mega-long one if your camera has "noise" problems.
Do you have light pollution?
Shoot in jpg, as card capacity has to be planned, too.
If you plan to include a foreground (trees, etc), you have to account for wind.

Free software? Look here.
http://www.startrails.de/

 

[agentgonzo]

If you (or your camera) have an "intervallometer" (timer, or similar) you can set it up to make a 30secs exposure every 40secs or so, around 90 shots per hour.

If you've got a canon camera, take a look at http://chdk.wikia.com/wiki/CHDK. You can run custom scripts (totally configurable intervalometer with no restrictions) on most non-EOS canon cameras. I've used it and it is VERY handy for time-lapses and multi-shot automations. Personally, I just use a shutter-release cable on my EOS.

Shoot in jpg, as card capacity has to be planned, too.

If at all possible, avoid shooting in jpg. RAW format (also available through http://chdk.wikia.com/wiki/CHDK if your camera doesn't support it natively) is vastly more powerful and records 16-bit pixel data rather than 8-bit jpeg, meaning you can fix a lot more in photoshop if necessary. Of course, the files are much larger but with a half decent-sized card this shouldn't be an issue for just shooting one night.

 

[Ripley]

RAW is better, but if you have hundreds of photos to retouch...ouch!!
It's better to set it perfectly up before, than having to retouch after.
If you go for one long shot instead, of course RAW is preferred.

 

[agentgonzo]

RAW is better, but if you have hundreds of photos to retouch...ouch!!

Programs like photoshop and Canon's fantastic DPP can do batch jobs on RAW-->JPG conversion.

 

[Ripley]

Ok
:hail:

 

[Artlav]

If only Photoshop could read CRW files...

Interesting idea, i'll try to take some pictures tonight.
I expect that a single exposure would suffice, as i was getting slight star tracks in 15 second exposures.

 

[agentgonzo]

If only Photoshop could read CRW files...

Search their website. There are plugins for Canon RAW image formats. My version of photoshop reads CR2s fine.

 

[JEL]

@agentgonzo;
@Ripley;

Whitebalance, yes. I hadn't given that a thought. I can see what you mean when doing multiple shots, if whitebalance is set to auto. That's going to go on my photo-checklist for startrail shots

* Manual whitebalance when doing multiple shots for stacking/layering. Check.

Yes, I was thinking about how to compose a startrail shot with a static foreground image, such as the one you show with the tree And my main concern with that is how to avoid getting the static part over-exposed while still allowing enough of the starlight to be captured.

I'm doing some tests at the moment:

Low ISO with long exposure... seems not to be ideal. The stars don't have enough time to imprint much light on the sensor-pixels before having moved to the next pixel, so the trails remain faint and few even after a long exposure, even though the foreground comes out beautifully and with very low noise.
I also found that light-pollution becomes a huge problem during long exposures. It seems light-pollution can be considered in the same way as a low-lit static foreground image.

Higher ISO with shorter exposures (layered in post-editing (startrails.de is amazing at that ))... seemed to make it easier to avoid over-exposing the foreground while still allowing enough light from the stars to come through (I didn't consider whitebalance on my first test of this though, so I'll have to try again)
What I did was a series of 30 second shots where I left the camera in auto-shooting. Basically like shooting video at a frame-rate of 1 frame, 30 seconds long, every 30 second. I had tall trees in the foreground and they got washed out (became blurry) because of their movement in the wind.
And then I layered them in startrails.de (super easy ) and thus only brightened the startrails and not the foreground or light-pollution, giving some really good results.
The only thing I found was that the short moment between each photo-shoot (when my camera saves the recorded image before beginning the next exposure) was just long enough to give visible gaps in the startrails every 30 seconds, making the startrail appear slightly dotted. Not a big problem though, because it was only visible when zooming the picture in to actual resolution (and obviously not a problem with startrails.de, but rather with how my camera can't multitask (shoot a new image while saving the previous at the same time))

I have a Sony A33, so the CHDK is not an option for me. I use a wired shutter-release so I can lock the shutter (it doesn't have an auto-timer or anything)
It seems this camera has very little noise-problems actually Even amp-noise is something I have a hard time producing with it (the purple glow on the edges of the image that people on photo-forums talk about in relation to long exposures). I was at first concerned with how much worse the photos would be when doing the auto-shooting, since the camera does not shoot and subtract dark-frames when in that mode. I can only get it to shoot dark-frames when using manual shooting. But so far that hasn't turned out to produce much difference in noise though, although I'm sure as the camera gets older and single pixels may start to go bad it could change.
It shoots 12bit raws or 8bit JPEG's. So far I'm doing most shooting in JPEG. And I use Gimp rather than Photoshop

Thanks for your feedback guys