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RC8 M81 processing and binning

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Hi all,

I've managed to get about 2 hours worth of luminance over the past few nights for M81. A mixture of 60 and 90 second subs with the ASI1600mm.
The scope still needs to be better collimated and the seeing wasn't great, but I was keen to start playing with the data I have until the clouds go away!

Because I'm quite oversampled with the RC8 and the 1600MM, I guess I really should be binning 2x2 to get the best image.
I think that because this is a CMOS camera there's no point in hardware binning, so it is better to do this in software.

I'm using Pixinsight, so at what point in the workflow is it usually best to bin the images? Before or after stacking? Before or after any sharpening?
Is software binning the image just the same as resizing, or is there another benefit?

The attached image hasn't been resized, just cropped a bit from the edges and some heavy handed processing :)



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Do it at sub level (prior to stacking), but you can always do each method and see if you prefer particular one over the others.

If you do it at sub level - each sub will have higher SNR, and all the algorithms related to stacking might perform better on higher SNR data (like frame normalization, etc). Only one that might work a bit worse is one that depends on resolution - registration process - it is probably easier to find star centers if they are at full resolution, but then again, improved SNR also improves centroid algorithms.

Binning should be done at linear stage, so try binning after sharpening the stack only if you sharpen linear data (and use screen transfer function to view results without actually stretching the data until you finish everything in linear stage and bin).

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Thanks vlaiv.

I'll give it a go before and after stacking when I get back, and see what the difference looks like.
Do you recommend the IntegerResample process to do the binning? I'm still very much in the beginner category when it comes to Pixinsight!

I think I should have put this in the "processing" sub-forum really!


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Yes, as far as I know IntegerResample should be the one to use to bin you subs.

I don't use PI, but I remember from some other discussion that this function should be the one for binning, let me check quickly.

Indeed, that's the one:


Just select average method

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Nice image! I look forward to seeing the final product, I just recently finished this one as well. I have a gso 8 RC as well and im currently using an atik 414. I was looking at the 1600 for my next camera. I know we will be pretty oversampled but despite that, how do you like this combination? pros and cons??

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Thanks! Looking forward to getting some more data for it when the weather gets better.

The RC8 is fairly new to me and I've only had it for a couple of months. I've been using the 1600MM on an ED80 previously, but needed to scratch the RC8 itch!

I'm liking the large size of the DSO that the RC8 focal length gives me with the 1600mm. Always wanted to get some close up galaxy images.
Despite the fact that I've not collimated the scope properly yet, and my guiding has only been OK-ish, I'm really happy with the combination. It was never going to be as sharp as with the ED80, but it's good enough for me. Hopefully even better when I get the scope collimated properly.

I view and process on a 4k laptop screen, and I wonder if that helps in making the images look nice and sharp at 100%

There may be better cameras if the RC8 was your only scope, but the 1600MM is the only CMOS camera I've tried so far, and I'm very happy with it.

Edited by evil_yoda

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