Star trails @ Castle Rock

[DaveB]

Please excuse me for two image posts in quick succession. I couldn't see anything in the forum rules about posting limits like we see on some other forums.


EOS 20D, 17-40mm@17mm

This is 4.5 hours of trails, looking directly south (obviously!). I'll give exposure details later if you're interested (anyone care to guess?).

I must say that keeping the trails from going jagged at this size is pretty tricky...

[leek]

That's a great photo... Feel free to link to a slightly larger one if you're having trouble with jagged lines...

[MHD]

Yikes.... well the stars have done a 1/4 turn so my guess would be 6 hours...
but it looks so clean..

Must have been dark there for the landscape to be so well exposed and not blown...

looks sureal..!

[darb]

if thast one frame, then its a true testament to one of the canon prosumer market strengths.

A d70 would require you do short length frames, and stack them later with stacking software. (even then, CCD amp oerheating would create a pink tinge and noise, meaning you have to run the NR job, which then creates a time delay and possibly adds gaps in the stars ... either that or you do it in say 10 second segments (still with NR, because if youre doing a bunch of 10 second shots in a row, the CCD amp will still heat up) ... meanign you'll end up with hundreds of thousands or images to go and stack ... a nightmare.

(all this from a very happy d70 owner)

[Oneputt]

Great shot absolutely love it. My guess is 4.5hrs Wouldn't have a clue though about apeture.

[daniel_r]

Darb,

My thoughts exactly - damn!

I've attempted similar shots like this and realistically you dont have any choice but to run NR... and waiting for the NR job can be a tedious process

DaveB - well done, great capture.
For this type of shot to work well, a lot comes into play such as a no breeze, low levels of ambient light in the foreground, a stable tripod and not having your front element dew up in the cold.

D.

[darb]

http://darb.net/ny04?page=2

some images on this page are night shots star trails ... single frames ... but with NR running, so i couldnt stack them (mind you i was half pissed) some are around the 20 minute mark.

It will be lovely when nikons d70 replacement / prosumer market moves to a cleaner / non over-heating sensor. (and its just aswell every other aspect of the d70 kicks butt ! )

[darb]

out of curiousity, how did you know where to shoot in order to get a perfect axis of the stars. Just facing north?

[lejazzcat]

I agree mate- Very nice !
Im very impressed with the canon - i regret to say .

[Killakoala]

Great image. Looks sweetly executed and shows heaps of patience. Great colours in the stars.

My guess is about a 2 hour exposure and a photoshop job with the foreground layer. It could be my eyes but some of the star trails look as if they are slightly on 'this side' of the ridge.

[DaveB]

No it's not one single exposure. 68 frames in fact.
The 20D can handle quite long exposures, but I wasn't sure how far I should push it. So I settled on 4-minute exposures at ISO200 (camera's base is 100) and the lens stopped down slightly to f/5.6. The Canon timer remote allowed me to take consecutive 4-minute shots (although the shortest interval between shots I could get was 1 second).

The resulting shots were stacked to produce the trails. I used ImageMagick with a Brighten compose operator that I added (I have a background in software development) to do this: if you had a Windows machine you could use Max Lyon's ImageStacker. It wasn't tedious (the RAW->TIFF conversion was batched, and then the stacking ran unattended) but it did take my laptop a while to grind through it all. I then brought this into Photoshop & cleaned up the few hot pixels scattered around the image. I shot without extra NR as the 20D (unlike the 10D and 5D) would do this with another 4-minute dark-frame exposure, making for very dashed lines.
This method of shooting star trails is not without its drawbacks however. 4 minutes equals 1 degree of rotation, and 1 second is 1/4 of a minute of arc. You end up with dashed lines (especially toward the edges of the frame) and although the gaps are very small, resizing algorithms preserve this as "important" detail. Max and I have compared notes, and the best solution I've come up with so far is to take a copy of the sky, rotate it very slightly (pivoting around the pole which is easy to identify) and blend it back in.

The foreground is actually another frame taken earlier in the evening. The whole thing is still an experiment: I'm toying with different white balances on the underlying shots, and using a different stacking mode for the foreground so I can use the actual night-time image there. Unfortunately it was a new moon so there was only starlight to work with.

out of curiousity, how did you know where to shoot in order to get a perfect axis of the stars. Just facing north?

North? South. It's easy to work out where due South is, and if you have a map or a GPS you'll know your latitude in degrees. That many degrees above the horizon is where the pole will be.
Work out while it's still light where the camera needs to be, and set up the tripod/etc. Then go back to camp (your cameras need to be far enough away so your camp lights, campfire smoke, etc don't cause problems). A couple of hours after sunset come out and start the cameras going (and find your way back to camp in the dark without getting lights in your shot). Then get up several hours before dawn and go out to turn the cameras off (unless the battery's run out in the night like it did with this image). I was doing this with several other people, and everyone else was using film. Funnily enough they were a bit more careful than I needed to be with not getting torchlight in their shots at the start/end of their single exposure...

[Willy wombat]

Thanks for sharing this technique with us. What an excellent result you have achieved. Congrats on a sweet pic.

[KerryPierce]

Excellent shot, Dave. Very well done!

[marcotrov]

Chamber's Pillar, Castle rock what a great location. Great image too, Dave! I'm always too scared to leave my camera out at night for such long periods. My luck a bat or night jarl would crap on it or nock it down.
marco

[DaveB]

Thanks for the positive feedback folks!

I'm always too scared to leave my camera out at night for such long periods. My luck a bat or night jarl would crap on it or nock it down.

I wouldn't be afraid of bats/nightjars: they're not going to fly into it in the dark! The concerns are mainly:

• Dew. This wasn't a problem on this trip but it's not unusual to use a shower cap on your camera.
• Dew on the lens can be dealt with by a small fan on a second tripod blowing across the front element. Depends on whether the conditions warrant it (it didn't on this trip).
• Dingoes. I know of one person who left their hat on the camera overnight instead of a clean plastic bag/showercap: because they'd been wearing it all day it obviously smelt interesting enough that dingoes knocked the tripod over and stole the hat (the other tripods near it were untouched). For similar reasons you need to bring your boots inside your tent/swag overnight!
• People. Obviously a nice camera on a nice tripod out in the middle of nowhere could be a tempting target for a thief. Out back there aren't as many people as closer to town, and in general they're not low-life. But why tempt fate: set your gear up well off the beaten track.

Lastly you could knock your own gear over! Finding your gear in the dark can be tricky (especially when there's no moonlight and you don't want to use a torch to avoid spoiling the shots - I have a trail of someone's headtorch in one of my shots from another evening) and people take different approaches:

• You can memorise your path from the camera back to the nearest trail (where you can then use a shaded torch) and leave a subtle marker at the turnoff.
• I know of one person who leaves a flashing red light (the taillight off a bike) on a foot of their tripod pointing backwards. But this would seem to invite visitors, so I don't advise this.
• I use my GPS, marking the locations (in daylight) of my tripod along with those of the other people I'm working with on the night. Then I don't have to leave any markers, and can find them from any direction.

One night on this trip we had a conga line heading out across a plain with me and my GPS in front, dropping people off at their tripods as we went...

[Greg B]

Great shot and very interesting details Dave. Thanks for sharing that detailed information.

We don't have posting limits here at this stage, it hasn't been necessary.