Wols Lists wrote:
On 28/12/17 13:44, Carlos E. R. wrote:
On 2017-12-28 13:51, Anton Aylward wrote:
On 28/12/17 05:25 AM, Carlos E. R. wrote:
Hi,
I have a bunch of sky photos with stars and some shooting stars (of 639 photos taken, 13 contain shooting stars, Geminids). I have seen photographs compossed of automatically joining several such photos so that you see one photo with a dozen(s) shooting stars.
How can I do that, in Linux?
(If not in Linux, then Windows)
The application I understand superposes several photos matching the stars one on top of the other (as dots) and the landscape, and then the shooting stars are seen as several lines.
Hopefully each image has a lot of the landscape in common so they can be aligned.
I didn't move the camera for the entire session, using a tripod. It is the sky which moves, ie, the Earth which rotates.
This might create some issues, as the position of the stars relative to each other will change due to lens distortions....
The worry is that HDR tools will be useless.
I think so, too. They assume unchanged scenery, and will at most handle the shooting stars as noise. So my approach to this would be: Load the photos in Hugin. Probably the autodetection of control points will not work, so you'd have to define some (more/many) manually. The more pairs you define over the FOV, the better can hugin determine the lens distortions an nicely map the images ontop each other. (hugin has a standalone align_image_stack program, you could try that first, but I don't expect it to work nicely for such images...) Then align the images, and export the aligned images separately (normally they would be removed after stitching - there's a 'keep' button somewhere in the stitch menu). Then they should all be really nicely co-aligned. Depending on the focal length of your camera you could use rectangular geometry (default would be equirectangular...) Load those in GIMP as layers, and set the mode of the stacked layers to 'lighten only'. That way the shooting stars will have proper intensity, which they wouldn't when doing averaging. You have to see how the (high-ISO) noise plays bad here - you'd also tend to collect the hot pixels this way. In doubt do some noise reduction on them before the averaging. Another try would be the GMIC plugin of GIMP. It also has a lot of fancy image addition algorithms (I especially like the median summing against hot pixels - but this would also remove the shooting stars...) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org