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First time since I got my telescope that i got a good view from Orion. The moon was quite bright so I was not expecting much, but gave it a try with short exposures without my Light Pollution filter. Since the exposures were short, I took an enormous amount of them. I got about 270 frames in various exposure times.

Once I was post-processing them, i found out it was impossible to align the frames. My pictures contained a unbelievable amount of hot and cold pixels. And they where all over the pictures, and in the same places in each picture. So the star detection algorithm was always detecting the bad pixels as the main stars to align. It was very frustrating.

I tried to relax the star detection algorithm, try to only detect big stars and structures, tried many different ways, and my image was never aligned. So i started to try to use “Cosmetic Correction” tool to remove the bad pixels from the reference image so I could use a cleaner picture to detect the reference stars. Also in vain. There was too many bad pixels.

Another idea was to make a “Star Mask”, and try to use it as reference to alignment. But even trying to fine tune the arguments of it was not possible to avoid the bloody hot and cold pixels.

I was about to give up, there was already a week of trials and errors and no signal of success.

Then i tried “Dynamic Alignment” where i could select myself each of the stars i want to use for alignment in one picture, and show the correspondent star in the second picture. That effort was a good one. It worked! The issue now is that this tool only align ONE picture… and i have 270 of them. It is not possible to manually do each one of them.

So I had a epiphany. I could do a couple of manual alignments just very few of them, and stack only those few pictures with a aggressive noise reduction settings to remove the bad pixels. And so, it worked. I had now a reference image without bad pixels that i could use for the real job of aligning the other 270 images.

So, after all that, this is the final result:


Orion Nebula (M42)
Celestron AVX 8″ SCT
Focal Length: 1278 mm
Aperture: f/6.3
ISO: 800
Shutter: 5s / 10s / 15s
Stacking: 99 / 96 / 41
Aquisition: BackyardEOS
Post processing: PixInsight
Taken Fev 27, 2015 around 20:52 CET

I used a very nice tutorial to edit this picture in HDR with distinct process for RGB and Luminance. And I must say, this is probably my best work so far.

I could to a lot better, in a Moonless night, with longer exposures and all, but for a sloppy photo session, and so many challenges for editing it, I am very proud of this result.