First Attempt Processing DWARF II Raw Images With Siril

A single 15-second "blink" image in Siril, selected from the raw FITS images. This is what all the unprocessed frames look like. Not very impressive on its own!

I took the raw images from my DWARF II telescope session that I showed in this blog post and processed them manually with Siril, using the steps from Ian Lauer's tutorial How To Shoot Deep Space With A Fuji (or any DSLR) Camera (starting at 20:07 in the video).

This involved manually "blinking" through 160 15-second exposures to eliminate the ones that had some kind of problem like clouds, out-of-round star shapes resulting from wind shaking the telescope, or streaks due to things passing through the field of view. That left 139 blink frames selected.

Then I took a small set of the scope's previously-captured dark calibration frames and ran the Siril OSC_Preprocessing script on them to align and stack the images. I had to modify the script slightly to skip the normal bias and flat frame steps.

"Stacking" means accumulating the data from multiple images to literally add up the photons captured in them, and also to cancel out the random noise that occurs in each separate image. The software has to match up and align the stars in each image to form the stack. So a pixel that contains starlight in each image produces a brighter pixel in the final stacked image, and a pixel that contains random noise where it should be black is averaged out to pure black.

That produced this stacked image of 2085 seconds of accumulated exposure, where you can start to see some color and the stacking process has eliminated the noise:

Then I performed the Histogram Transformation image processing step to "stretch" the image. Most of the image data is jammed up against the left-hand side of the image histogram; technically, "stretching" means adjusting the histogram to stretch out the data to the right to fill most of the histogram. Visually, this means enhancing the very faint data in the dark areas to make it visible.

That produced this final image:

For comparison, this is the final image that the DWARF II produced via its own automated internal stacking and stretching (this is the image from that other blog post):

I'm pretty pleased with the results. The automated image is brighter and more colorful, but overall my manual processing with Siril has produced a decent image from the raw data. That means when I'm processing raw data from other cameras, I'll be able to produce a good final image.