A IR cut filter is attached to the webcam, but it is positioned too far away from the CCD chip to be fully effective. This is caused by unwanted infrared light reaching the webcam sensor. The first noticeable characteristic of the video is a strong pink/purple colour cast on the edges of the frame. This presents some extra challenges, but as can be seen, still allows for great results to be obtained with minimal expense. Most astrophotographers will spend £100 or more on CCD cameras directly designed for use with telescopes, so this modded Lifecam is very much at the low end of what can be used. The source material for the blog post is a 40 second long video captured with a modified Microsoft Lifecam HD paired with a Celestron Nexstar 4GT telescope. What follows will pick up immediately after stacking has produced a merged image, and show how GIMP and G’MIC can replace use of the closed source, Windows based Registax tool. Use of AutoStakkert2 can be a blog post in its own right, so won’t be covered here. A common tool used for this is Registax which particularly found popularity because of its wavelet sharpening feature. The output of AutoStakkert2 though is not a finished product and requires further post-processing to correct various image artefacts and pull out the inherent detail. A program such as AutoStakkert2 will then process the video, analysing the quality of each video frame, selecting the “best” frames, and then merging them to produce a single frame with less noise and more detail. Instead normal practice is to capture a high definition video at a high frame rate lasting for a minute or more, by attaching a webcam to a telescope in place of the eyepiece. The long awaited GIMP 2.10 release in April 2018, introduced 16-bit and 32-bit colour channel support, along with many other important improvements that enable high quality post-processing.Īstrophotographers seeking to present high detail images of The Moon, have long recognised that capturing a single still image is not sufficient. GIMP has been largely ignored by astrophotographers in the past since it only supported 8-bit colour channels. This post is going to illustrate a post-processing workflow for lunar surface images using the open source tools GIMP and G’MIC.
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