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M13 Great Globular Cluster in Hercules


mightymonoped

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Added another 1.5 Hrs to this on Wednesday night in windy and mediocre seeing. Bringing total capture over 4 sessions to approx 9 Hours.

This was stacked and brutally culled down to 7 hours in Astro Pixel Processor, using its excellent Analysis Graphs. Then used APP to reduce Light Pollution before passing honours to Pixinsight.

 

Ran a SPCC against the image and then a minor NoiseX before a 'restrained' BlurX deconvolution followed by a full NoiseX.

 

Then ran a Super Hyperbolic Stretch using the BB stretch tools before saving the resulting Tiff file and passing final duties to Photoshop.

 

First a push on Colour Saturation using Image/Adjustments/Match Colour.

 

Finally, used AstroFlat Pro Plugin to sort out the problems caused by rubbish flats over 4 separate sessions.

 

Tony

M13-Apr21-2023-crop.png

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There's a lot to like about this. Right towards the middle of the cluster, though, I think you're saturated. That means that everything is at the maximum value of the screen. I think it's unlikely that this will be true of the individual subs - though looking at them in linear form will tell you. If there is a range of brightness visible in the core of a linear sub, that range of brightness can be preserved in the stretch. It just requires super careful control of the stretch, possibly using Curves rather than a generic Levels stretch.

Olly

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22 minutes ago, ollypenrice said:

There's a lot to like about this. Right towards the middle of the cluster, though, I think you're saturated. That means that everything is at the maximum value of the screen. I think it's unlikely that this will be true of the individual subs - though looking at them in linear form will tell you. If there is a range of brightness visible in the core of a linear sub, that range of brightness can be preserved in the stretch. It just requires super careful control of the stretch, possibly using Curves rather than a generic Levels stretch.

Olly

Thanks Olly,

That was something that was worrying me if I’m honest. I did try to use the core as the guideline in the stretch but only visually, didn’t really look at it properly it seems. 
 

I’m planning on doing it again anyway (with some better flats) so will approach it a bit more carefully next time. 
 

Thanks for the advice 😊👍

Tony

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5 minutes ago, mightymonoped said:

Thanks!

I used my old Skywatcher 80ED (gold) with ASI294mc pro and L-Pro filter, running on an EQ6-R Pro with ASIair Pro. 

Really! I’m impressed. I might have a go at this target with my Evostar 80ED pro.  Same focal length as the gold I think.  I’m guessing it might be worth taking off the focal reducer/flattener just to get a slightly bigger image, and stars at the image edge can be cropped off for M13 anyway. 

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50 minutes ago, Ouroboros said:

Really! I’m impressed. I might have a go at this target with my Evostar 80ED pro.  Same focal length as the gold I think.  I’m guessing it might be worth taking off the focal reducer/flattener just to get a slightly bigger image, and stars at the image edge can be cropped off for M13 anyway. 

It would make sense to do that but I didn’t bother tbh. 😊

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