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Garnet Lake Star Streak [41_00656] | by Steven Christenson
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Garnet Lake Star Streak [41_00656]

This is a reprocessed version of this photo. So what has changed in over a year since it was taken?


I used a newer version of Digital Photo Professional [DPP] which comes with better noise processing. I got better at Photoshop so I made a single image HDR using the foreground as one shot and the sky as the other. Basically it means I darkened the sky and lightened the foreground and recombined them. I also did some "healing" on the many remaining noise spots to fix some glaring issues.


it's still noisy and fuzzy. Part of the fuzziness is due to the tripod and head that I used - it was not the most stable of scenarios.


Wondering what that glow is on the horizon? It is from the recently set moon.


As I noted in the original posting, the EXIF data claims that this was a 26 minute exposure. I think it was much longer for a number of reasons. The first is that the lens was at 19 mm. On my 40D that lens has a vertical field of view of 60 degrees. Conservatively, 20 degrees of that are sky in this photo.


It takes a star at the Celestial Equator one hour to go 15 degrees (and that will be diagonally as shown here). Unfortunately there are no trails that both start and end in this one view, so it is not possible to extrapolate exactly how long the exposure was... but clearly it seems to have been longer than an hour so I'm going to stand by my original 2 hours and 15 minutes statement.


You might wonder why I don't know how long this was... the answer is because it was the first time I used my timer to run an exposure this long and I was asleep (well, trying to sleep) at the time. Moreover, the theory is that the internal counter for the exposure time overflowed (lied to me!)... so the exact number is unknown.


I'm headed to the high Sierras real soon now and hope to come back with an even nicer version of this style shot. The moon will be very cooperative, setting around midnight.


Meanwhile you can take a look at the larger image and smugly note that there is still a lot of noise.


Since this image, I seldom take exposures longer than 8 minutes and use a process to stack my long exposures to get composite trails. Noise is less of a problem with shorter exposures, and it is possible to keep the sky glow manageable. I write about this in my BLOG, and teach workshops on my techniques, too.


For an example of a stacked shot, see this or this


© Copyright 2008,2009 Steven Christenson

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Taken on August 10, 2008