Star Trails.

docbell · November 21, 2006

This is my first attempt at star trails, taken in the Sierras. It wasn't ideal conditions as it was very windy when this was taken - you can see some motion blur to the tree and I think Polaris and the star trails themselves would have been much sharper if there was no wind. Patience, and a full camera battery, seem to be important aspects in taking these shots.

Details: RebelXT, 24-105 (at 40 mm), f6.3, iso200, 28.6 minutes, RAW, tripod, shutter release, MLU.

Comments and critiques welcomed.
Kevin.

mushy · November 21, 2006

docbell wrote:

This is my first attempt at star trails, taken in the Sierras. It wasn't ideal conditions as it was very windy when this was taken - you can see some motion blur to the tree and I think Polaris and the star trails themselves would have been much sharper if there was no wind. Patience, and a full camera battery, seem to be important aspects in taking these shots.

Details: RebelXT, 24-105 (at 40 mm), f6.3, iso200, 28.6 minutes, RAW, tripod, shutter release, MLU.

Comments and critiques welcomed.
Kevin.

What if any post processing have you done to the photo? as I have tried similar with a 20d and ended up with a fair amount of noise. also what ambient light etc. I'm intrigued as this has come out quite well. Maybe hitting the tree with a flash or a light of some sort just briefly would give it some detail rather than just a black blur.
Just some thoughts...

kres · November 21, 2006

This is one of those shots I really want to try to take.

I love the way that the color of the stars is so much more apparent with the timed exposure.

:lurk Looking forward to the techincal discussion on this one.

docbell · November 22, 2006

Mushy, the only post-processing done was a decrease in the exposure (to darken the sky a little), and a little bit of increased saturation and USM.
Additional technical info that I forgot to put in the initial post was:
1. Bulb exposure (obviously to be able to get that long of an exposure)
2. Long exposure noise reduction (if you havn't used this for your star trail shots, try it next time - I think you'll see a dramatic decrease in the amount of noise in comparison to your previous shots. But, this is where it is important to have full batteries, as the in camera long exposure noise reduction will take the same amount of time as the actual picture did).
As far as lighting up the tree, I actually did 'paint' it with a flashlight for ~ 5 seconds. This was obviously not enough time, but as this was my first try at star trails, I wasn't sure how long to paint (I was worried about overexposing the tree). Trial and error I guess, next time I might paint the foreground object for, I don't know, 20-30 seconds. (Anyone else have any ideas how long objects should be 'painted' on shots like this??

).

Kevin.

schmoo · November 22, 2006

I have to disagree in that I think lighting the tree may have made it stand out a bit too much (more than the stars) - not to mention then I think it would look a bit "off" since the light would be shining up and not down form the sky - but then again if it were done well my mind about that could be changed.

I only have limited experience in light painting, and found that a little goes a long way. This one, for example, was for a 30-sec exposure in a completely dark room and I think it turned out a little bit too bright in some areas for my taste. Maybe it was the fresh batteries in the Maglite?

But 30 seconds is nothing like your 30-minute exposure there, so I doubt this is of much help.

Awais Yaqub · November 22, 2006

Very cool ! loved them

gus · November 22, 2006

mushy wrote:

What if any post processing have you done to the photo? as I have tried similar with a 20d and ended up with a fair amount of noise. also what ambient light etc. I'm intrigued as this has come out quite well. Maybe hitting the tree with a flash or a light of some sort just briefly would give it some detail rather than just a black blur.
Just some thoughts...

Mushy are you setting the camera to its 'noise reduction' setting #2 in the custom functions. I have had great results with it.

** Remember that in this function if the exposure is 46 mins 51 seconds then the write to card time is also 46 mins 51 seconds so dont do as i did at first & assume your camera is cooked. This also means that a large well charged battery is req for the job as you are looking at a long time between hitting the button & the camera finishing its write.

mushy · November 22, 2006

gus wrote:

Mushy are you setting the camera to its 'noise reduction' setting #2 in the custom functions. I have had great results with it.

** Remember that in this function if the exposure is 46 mins 51 seconds then the write to card time is also 46 mins 51 seconds so dont do as i did at first & assume your camera is cooked. This also means that a large well charged battery is req for the job as you are looking at a long time between hitting the button & the camera finishing its write.

I haven't done an overly long exposure using setting #2 yet. Just 20 min approx with varying results on standard bulb setting. My only other question would be why go ISO 200? are you not adding more grain by upping the film speed or is it more proportional to the fact the shutter needs to be open for less time

USAIR · November 23, 2006

Been trying my hand at this too.
I love your results very nice good job

Fred

SloYerRoll · December 5, 2006

mushy wrote:

I have tried similar with a 20d and ended up with a fair amount of noise.

Another thing that might help is location. I'm not sure of any exact numbers, but you have to be really far from any city or big light sources (like 100 miles+). Kevin was in the Sierras and was probably away (and above) any ambient light that would harm this exposure. Even at this location, he had to compensate in pp.
As far as I have seen and read. Ambient light is the main killer of shots like these.

gus wrote:

** Remember that in this function if the exposure is 46 mins 51 seconds then the write to card time is also 46 mins 51 seconds so dont do as i did at first & assume your camera is cooked. This also means that a large well charged battery is req for the job as you are looking at a long time between hitting the button & the camera finishing its write.

Thanks for that tip Gus. I never thought about it.. I would have definately thought my unit was toast if I had to wait that long...