Help With Settings for Star Trails

Discussion in 'Astrophotography' started by Turbofrog, Jun 2, 2015.

  1. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    So I tried my hand for the first time at star trail photography the other week. I screwed up enough of the settings that I wasn't particularly happy with the results, so given the rare opportunities that I have to do this kind of thing, I wanted to pick the brains of the more experienced photographers on here a bit...


    This was taken on a GX7 with the 7.5mm/f3.5 fisheye. This is about 25x exposures stacked, processed, and de-fished. They were taken at f3.5, ISO 640, and 60 seconds (longest I can do with the intervalometer). I converted to B&W and added grain because I was quite disappointed with the noise I was getting, even with a dark frame subtraction (there's a lot of seriously purple charge leakage around the edges of the frame before subtraction - I was shocked).

    You'll notice that there are some gaps...I screwed up the intervalometer settings so I had 30 second gaps in between the frames, so I tried to fix that with some radial blur.

    So my question is, what sort of methodology should I be using to get better results?

    1) How much gap is necessary to leave in between intervals to ensure the files can be written? 1 second? 2? 3? (0 can't be set, so I assume it needs at least a little time to process/write the file).

    2) Is f3.5 fast enough to use a lower ISO, or would I need a faster lens to do this kind of shooting? I was just having trouble picking up the stars, but I was previewing it on a screen, so maybe I would be able to pick it up when PP'ing the RAWs...

    3) ISO 125 or ISO 200? Will there be a big difference between ISO 640 and base/low extended ISO for this kind of photography?

    4) Best methodology for dark frame subtraction? Even if I have to deal with gaps, are the results better from the in-camera long-exposure NR than doing it manually with a dark frame? It's certainly more convenient...

    Thanks in advance for any help!
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  2. BeyondTheLines

    BeyondTheLines Mu-43 Veteran

    Sep 23, 2012
    I'm no expert and I've only tried star trails a couple times a couple years ago so I'm just answering from memory. Maybe someone with more experience will chime in.

    1. the least amount possible. On my E-M5 I would use the anti-schock function with 1/8th or 1/4 second I believe. More time in between shots does have the benefit of letting the sensor cool giving less noise but if you're stacking, noise shouldn't be too bad.

    2. f3.5 should still be ok (faster would be better) but you'd probably want to bump ISO up a bit more.

    3. The higher the ISO the higher the signal, meaning stars will be brighter but at the expense of more noise. Since you're stacking you should have some headway with noise but I'm surprised you said noise was a problem using ISO 640, maybe your blending method needs tweaking.

    4. The best is right after each shot since the noise pattern is ever-changing especially as the sensor temperature changes. However, this isn't practical because you'll get gaps in your star trails so I would just take some shots with the same settings before and after at the same settings but with the lens cap on and then blend them in post.
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  3. Lcrunyon

    Lcrunyon Mu-43 All-Pro Subscribing Member

    Jun 4, 2014
    Great first try (even with the mistakes you pointed out, it's still a pretty cool shot), and good follow-up questions. As someone who would someday like to explore astrophotography myself, I'm also interested in what advice you'll get. Bravo!
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  4. edmsnap

    edmsnap Mu-43 Veteran

    Dec 20, 2011
    Edmonton, Alberta
    The sensor noise that you're creating with multiple long exposures is typically way harder to deal with than high-ISO noise in shorter exposures. Give it a shot at ISO1600 or 2000. This is the best link I can find quickly with some examples of what I'm talking about in terms of long exposure being worse for noise than high ISO:

    Sample sensor noise images

    Using a higher ISO, getting good exposure on the stars, and then dealing with the noise in post could give you significantly better noise results. Something like DXO Optics Pro makes big promises about eliminating noise from astrophotography shots. I've used it a little bit with good results.

    Post-processing video

    Using any lens wide open usually means accepting some optical problems. Again, I'd deal with some higher ISO to try stopping the lens down a little to eliminate CA, coma, astigmatism.

    Such would be my thoughts :)  Good luck and keep us posted on your results!
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  5. The Samyang is good enough wide open for this sort of thing IMO. My normal setting for not getting star trails with the 7.5FE is f/3.5, ISO1600-3200, ~20s exposures each. Stacking even 8 of those gives pretty good noise performance. For my purposes I do dark frame subtraction in camera, but that only works because I'm aligning the stack without trails. You probably want to stick with doing them separately.

    What are you using to stack, and do dark frame subtraction?
  6. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    I'm using an old piece of freeware called Blackframe NR for my dark frame subtraction, but it doesn't do batch processing, and the only results that I liked were from the "Simple Scientific" subtraction, method, so I could likely get the same result using the Difference layer in Photoshop that I'm using for the stacking. Stacking is just with Lighten, and then a bunch of stamped layers and masks and yada yada yada...

    I think part of the problem is that this time around I used the original JPEGs for processing, and I really don't like OOC JPEGs because I hate NR artifacts. I'm guessing I probably would have gotten better results with LR processing RAWs, or with Topaz DeNoise, but didn't want to put the time in for this image since I knew it already had other problems.
    Last edited: Jun 3, 2015
  7. maritan

    maritan Mu-43 Veteran

    Oct 30, 2014
    I've got a few tips, but not time right now. Quick hits:

    1. Try StarStax freeware. Available on Mac, not sure about PC. Does dark frame subtraction
    2. Try Live Composite mode. Fantastic mode to get star trails in camera. I usually do a test shot at a VERY high ISO (25kin regular mode to see if my composition is correct. Then, I bump down to my preferred ISO (usually 200) and try a long duration exposure <60" to see if I can get a decent exposure - again in regular mode. Then, I use that setting for Live Composite and go from there. One such result:

    16818682228_72744d806d_c. P3280262 PS Edit
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  8. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Ooh, thanks for the software recommend. Looks good, and should really speed things up. It is available for Windows, too, so that's a plus.

    Unfortunately I don't have Live Composite mode on my Panasonic. How long was that exposure above? And did you take the foreground separately from the star trails? That was going to be my other thought...leave my tripod out in the right place and take a post-sunset/blue hour exposure to get a nice foreground, and then layer on the star-trails a few hours afterwards when it gets nice and dark.
  9. maritan

    maritan Mu-43 Veteran

    Oct 30, 2014
    About 40 something minutes in "one" shot. It was a moonlit night, so no need for separate exposures. There was also some light painting involved - subtle (hopefully) but involved.

    The other way to do it is to use your intervalometer to figure out the right time duration. Separation between shots on my Olympus is 1 second. While the camera is still writing the previous shot it starts the next one, no issues. No long exp noise reduction obviously. Post dark frame reduction with StarStax.

    ETA: Here's an example:

    P3270069-P3270099_lighten Comet V2

    I used a 90 second exposure with 1 second between for a total of 32-35 or so shots.
    Last edited: Jun 3, 2015
  10. Raw is definitely better. Software makes a big difference too - depending on the stack mode you'll actually get a noise reduction effect on the static elements. Not sure if a simple lighten will do that or not.

    Live composite does a stack in camera of a long sequence of shorter exposure intervals on the fly. The bright stuff that changes get added, while the did that doesn't gets noise averaged out somewhat.
  11. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
  12. NoSeconds

    NoSeconds Mu-43 Hall of Famer Subscribing Member

    Best thou rectify thy situation verily... :biggrin:
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  13. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    The StarCircleAcademy has basically written the book on how to do this. Read through their stuff for lots of details & hints.

    On my E-M5, a typical charged battery will -if its not very cold - last me about 250 min. of intervalometer star trails shooting before its dead. Be aware completely draining Li batteries is pretty hard on them & shortens their life - especially non-chipped 3rd party ones.
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