I’ve had good luck with GIMP and the Star Trails Script but I’ve head great things about StarStax. Anyone have luck with it? I can’t get it to open any files on Ubuntu 16.04. I read it might be a problem with permissions but the same files open with GIMP so I can’t figure out why they won’t open for StarStax. Anyone using it or something else they like?
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I’d be interested to hear what others have had experience with as well. Folks like @Jonas_Wagner keep posting these amazing astro images that I really want to try out some day soon.
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I’m interested, too. But the best way to prevent star trails is a tracker (if you can afford it) or obey the “500 rule” and maybe do a median stack.
@floessie I think he wants to capture star trails not prevent them. With that said I also usually want to prevent them.
The usual method for capturing star trails is to use max/lighten blending. But that results in a lot of noise and doesn’t get rid of disturbances like airplanes.
It seems to me that the ‘right’ way to do star trails would be to:
- Do a regular stack for the foreground
- Do another stack with the stars aligned
- Reproject the aligned star image back to the original (non rotated) positions and then blend with lighten
- Merge foreground and stars
That should get rid of most of the noise (at least in the sky where I find it most disturbing), air planes and other disturbances.
Gap filling could then also be easily done by just reprojecting more image with interpolated transforms.
I don’t know any software that does this (as of now). I thought about writing my own little astrophotography tool one of these days. If I did write it one day, this should be an easy addition.
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David, where did you get your version of StarStax?
I’ve downloaded the latest compiled version but I’m running Gnome 3 and not KDE, the first failure is a call to a kde lib. 
Actually my bad, it’s a lib gstreamer. The downloaded compiled version was for Ubuntu 13.04. 16.04 has much later versions.
I can’t remember why but I started using the Windows version with Wine. It has worked perfectly.
OK, thanks. Installing Wine as I type. 
Just checking I’m not making this harder for myself than it should be, but was it just a case of downing and running StarStax or did you have to do a bit more to get it to work on wine?
I’ve downloaded the 64bit windows version and wine is complainnig about a the dll’s missing.
OK, just to follow up on my ramblings, I’ve installed the 32 bit version and it works fine.
Please do not perpetuate the myth of the Rule of 500. The is only one scientific way to expose in order to preclude star trails. Here is a short paper that I posted on Dpreview regarding this topic.
The Rule of 600, 500, 400 etc is just convenient tool to guess at a starting exposure time. Most of the people who espouse the Rule of 500 suggest adjusting the time in order to achieve a satisfactory star trail. If the Rule of xxx was scientifically based there would not be any variants (Roger Clark suggests using a Rule of 200). There is only one scientifically correct way to estimate the star exposure time; it is based on the time it takes for a star to transit a pixel (not the sensor) and the level of star trail you are willing to accept. If you were on the equator and have a full frame camera with a ~ 4-micron pixel and a crop camera with a 4-micron pixel, the time to transit the pixel would be the same, about 3.3 seconds. It is based on the pixel size. On the other hand, a camera with a 6.4-micron pixel (regardless of sensor size) would have a star transit time of about 5.3 seconds. Several authors have suggested a two to three-pixel smear is acceptable. One pixel exposure would produce a perfectly round star, but because of limitations of human visual acuity, the star would be hard to see. Bottom line, if you have a camera with a 4-micron pixel and allowing for 3 pixels of trail, you would want to expose for about 10 seconds; a camera with a 6.4-micron pixel, allowing for the same 3 pixels of trail, could be exposed for ~ 15 seconds. If you were at the North pole looking straight up, you could expose for a very long time regardless of pixel size.
Many web site authors dogmatically state that you should use the crop factor with the Rule of 500. Optical physics shows that the crop factor does not affect the focal length of a lens, there is absolutely no reason to include it in the calculation, other than the fact that sometimes it gives a better answer (but sometimes it can make the star trails worse.)