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Walking on the Moon

Leo Triplet with added data


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I managed to get some more data on my Leo Triplet project. 1 hour of Hydrogen alpha in 10 min subs plus 40 min each of RGB, also in 10 min subs. Surprised I can manage 10 min through my LP, so that's 1 hour 40 min each RGB in total, plus 1 hour h-alpha


130mm Photoline triplet with 0.75 APM reducer, Baader filters and Trius 694. Stacking in AA5, Sigma Average, flats and bias, I think I need to check my flats, redo the hydrogen in particular, and I'm *still* getting burned out cores. Will look into getting a trial license of Pixinsight, to give it a go.

I used Gradient Removal, linear and vignetting before stretching each stack, then combining using the RGB Trichromy tool finally cropping to get rid of misaligned borders. I may have a go at doing the combining before stretching, to see if that can help.

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Looks like you have good data there, so your equipment is working well and the sky cannot be too bad, but as you say you burn out the cores (and you are making the stars bloated). You need to protect the cores and also the stars when you stretch the image. Not sure what program you use for processing. It is easily done in PS (select the bright areas = stars and cores and invert the selection before stretching in curves - best done in a few rounds with making a new selection of the brights and invert it each time) and I am sure also in PI (which I have never used). That would make a being difference to you image.

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Thanks guys.

The only software I use for processing ATM is AstroArt5 which is fine for stacking and trichomy but I think a bit lacking in the more advanced stuff, though it does have a star shrink function.

I'll have a sleep on it and do another run tomorrow, also looking into PI, though I have a huge amount of work to do around the house that's built up waiting for the hols.

As for my skies, I'm in the north-west London suburbs. NELM in the direction of Leo was somewhere between 3.5 and 4, probably nearer 3.5 and getting worse as the days went on. The hydrogen data was taken with the moon starting to get a bit bright.



Hmmm......thinking.....I was a bit lackadaisical where focusing was concerned, just getting it spot on for Green, and hoping that the other filters wouldn't be too far off. This was mainly because my GOTO was to the bright star in the group, which I would then have to decenter to get the three galaxies nicely framed, leading to alignment errors every time I slewed away and then back.

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Well, I gave the data another bash.

Did the H-alpha stack without flats as they seemed to be adding to my problems, then used Remove Gradient > Adaptive Subtract on all the stacks. This did a better job of flattening the background.

Added the H-alpha to the Red channel after aligning, but didn't do a histogram stretch.

Used the Trichomy to construct the RGB image, and ticked White Balance to clear a slight cast to the background. Cropped the image to get rid of the alignment errors.

Did a DDP on the data, looking carefully at the bright star in the middle to avoid either bloat or haloing which can occur during DDP, then a mild histogram stretch with gentle curves to boost local contrast, finally a slight LPF for noise reduction


So what do people think? Comments and constructive critique welcome. I could do with more data, but I fear that by the time the moon gets out of the way I'll be looking at Markarian's Chain.

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