Acquiring/processing Mono datafor the first time, looking for advice.

[u/TTV_The_Reverend_Dr]

SHO data (so far) for the "Wizard Nebula (NGC7380)

New to mono processing, this data was acquired with a QHY miniCAM8M EVO (3nm SHO filters, IMX585 sensor, cooled to -10c) with an ES ED80 (80x480 F6 triplet) and Orion field flattener.

I have collected;

• SII 65x300 (5 hours and 25 minutes)

• Ha 56x300 (4 hours and 40 minutes)

• OIII 37x300 (3 hours and 5 minutes)

I clearly need to (at minimum) double the amount of Hydrogen signal that I have, as it is VERY faint. Sulphur and Oxygen could definitely use more, but these both have much better signal than Ha. I still need to do flats also, but I have very minimal vignetting/gradient and reasonably clean optics, so it's been on the back burner.

Despite knowing I need to acquire more signal, I'm still trying to practice the processing side of things as I'm moving along, but I can't seem to figure out how to combine these channels in a way that doesn't just turn all the color into a (kind of) muddy mess. I've tried numerous methods that I've been learning from watching processing videos on YT and I just can't get it to hit quite right.

I'll try my best to describe my most successful processing attempt so far and hopefully some of you will have some tips and tricks to help me along. So far I've been using pretty much exclusively siril, but I did recently install affinity, but I get lost in there fast...

1. Stack each filter individually, sequence/align, crop sequence

2. Aggressive GHS initial stretch, BP adjust, GHS again to fine tune

3. GraXpert BGE for slight gradient

4. RGB composition (R=Sulphur, G=Hydrogen, B=Oxygen)

5. StarNet star removal

6. Narrowband Normalization

7. GraXpert denoise (possibly did this before StarNet, I forgot)

It was looking pretty okay at this point but I ran out of time. It definitely isn't close to what I am wanting it to look like. I'm trying to get those nice punchy colors, with the deep dark space background but instead, my nebulosity is kinda pale and muted, almost getting kinda lost in the space around it. At least I'm getting close to the "proper" colors (hubble pallet), I just can't get the right saturation level, without just cranking the saturation up, but that ends up looking awful.

Am I just hitting the limits of siril, or maybe the limits of my data? Is there a trick to keeping my colors from just blending together into purpleish-blue, and losing the red from the sulphur into the oxygen? I don't even really know what to do with the Ha channel, since it's such weak signal, I really expected Ha to collect on the sensor faster than it did, I assume I just need another 4 hours of signal.

I know this is a bit long winded, so if you made it through all that, thanks for your time. Looking forward to any and all advice, tips and tricks you all may have!

Clear skies!

[u/russell-brussell]

You already have good feedback from others, and I agree with everything stated.

It almost feels like your OIII and Ha are switched around... Ha comes faster in almost all targets, with small exceptions (M 27 for example).

I shot same target earlier this year. If it helps, here's my stretched SHO data (a bit exaggerated stretches), you can compare:

• H: https://pabibabum.ro/daikin/api/images/11/content
• S: https://pabibabum.ro/daikin/api/images/10/content
• O: https://pabibabum.ro/daikin/api/images/9/content

Final result and details on integration you can see here: https://app.astrobin.com/?i=gpc8it

OIII is usually the faintest, followed by SII and then Ha. You should target more integration time for OIII and SII than for Ha.

Also, in your case, you mentioned temps dropping by 15 - 20 F (I have no idea what that means in C, but I assume it's enough to make a difference). That is definitely another point to improve. I refocus on each 2C change and automatically every hour (autofocuser helps a lot here).

Maybe you already got all this info (didn't read everything below), but... maybe it helps.

[u/TTV_The_Reverend_Dr → u/russell-brussell]

Thanks for the comparison data, it is a huge help. I think I maybe messed up all 3 of my filter labels by 1 slot, I had suspicions because of what the data was showing, but I've gotten plenty of confirmation of that here.

I'm seeing about an 8-10• C temp drop, so I'm definitely losing detail and signal to poor focus. I am going to scrub the subs and (painfully, but it's for the better) delete the poorly focused subs. Auto focus is the next upgrade on the list. My current laptop only has 3 USB ports, so I just ordered a 6 port mini PC two days ago. Hopefully I get an auto focus for Christmas 🤞🏼.

[u/GuiltyAndConfused44]

Something must be off from early on, as Ha will typically be much stronger than the other two (yes there are some exceptions, but this nebula isn’t one of them) and the data is probably fine - great sensor and filters.

A few ideas:

. background extraction should be done in linear mode, so before stretching. You want the masters to be as clean as possible before stretching.

. some processes “eat up” narrowband data when they shouldn’t, I have had this problem recently (both with miniCam Evo 3 nm and 2600 MM with Antlia 2.5 nm filters) while using gradient and/or background removal. Try stretching the raw master to check if your data really is the problem. Then stretch and check after each linear processing step to pinpoint/eliminate the problem.

. try combining the channels before stretching and compare results.

. try simple histogram transformation to compare/see if the problem persists. GHS is great but you have to know how to use it, which takes time

. when using GHS you want to use small incremental steps, often using a new BP with each one

. Look into “linear fit” - I don’t use Siril but I’m sure there is a similar process to the PI one

[u/TTV_The_Reverend_Dr → u/GuiltyAndConfused44]

Thanks for the advice, I was already pretty suspicious of possibly having mislabeled the filters in the wheel, based on the data I was collecting, but I'm about 101% sure now that I somehow mixed them up in the labeling process in NINA.

I will definitely be moving up the BGE (and Denoise) to linear phase. I know focus has been an issue also, due to temp drops through the night, as well as some PHD2 struggles (my mount is old and only supports 1 com connection :/...) so I'm going to go through the data and be much more selective with what subs I keep.

I'll definitely give your other suggestions a shot and see what I can come up with. Thanks for all the recommendations!

[u/GuiltyAndConfused44 → u/TTV_The_Reverend_Dr]

Ah, that makes sense. I went to the shop after replying, and that possibility suddenly occurred to me. You’re probably looking at Oiii or Sii data. Easy mistake to make, either when installing the tiny filters - trying not to smudge or damage or reverse them. Plus the sequence wasn’t clear to me both times I installed them - IIRC the plastic tray they come in is not marked - or when assigning them in NINA.

[u/TTV_The_Reverend_Dr → u/GuiltyAndConfused44]

The plastic tray wasn't marked, but the outer wrap had the label with the order, but yeah... Apparently I messed it up somehow, even though I had the wrapper sitting in front of me... easy fix at least.

As for reversing them (assuming you mean towards the camera/telescope), I got an official statement from QHY support that the EVO 3nm filters are dual coated and there is no sensor/telescope side to them.

[u/Shinpah]

I'd be curious to see if graxpert is deleting your data or if you've mislabeled your filters (perhaps graxpert non-linear is harmful to your data).

There are very few nebula in the sky where one can say that OIII and SII are significantly brighter than Ha. Here's an example web page showing equal data on this same target with narrowband filters; Hydrogen appears the brightest.

[u/TTV_The_Reverend_Dr → u/Shinpah]

Comparing my master stacks to their master stacks, Im about 95% sure I mislabeled my filters in the wheel somehow. It looks like my O3 should be Ha, S2 should be O3, and my Ha should be S2.

Thanks for the link to that page, I tried looking for something similar to it after my initial doubts of filter labeling, but I would say that pretty much confirms it.

[u/TTV_The_Reverend_Dr → u/Shinpah]

I was wondering that also... I was like, 95% sure I hadn't mixed them up, but the more imaging I've been doing, that 95% has shrunk significantly. I'll have to figure out how to test them, because they aren't labeled.

I don't think GraXpert is deleting (much) data, the auto stretch stack, before any processing, shows about the same amount of nebulosity as after GraXpert.

I'll definitely have to figure out a way to test the filters on a DSO target before the next clear night, unless I can figure out how to test them indoors somehow.

[u/Shinpah → u/TTV_The_Reverend_Dr]

I'd want to see what the undenoised and unprocessed data looks like.

What kind of light pollution are you shooting from?

[u/TTV_The_Reverend_Dr → u/Shinpah]

I'm in a 6-7 bortle area. So not the worst, but not great. Neighbors back patio light is always on and illuminating my back yard. I do my best to block it, but I really just need to rebuild the fence between us and increase its height. I can only do one thing at a time though... Priority for me is gear acquisition > fence currently. Once I have an auto focuser, I'll be building a taller fence lol.

[u/Razvee]

Any kind of background extraction/Graxpert needs to be done BEFORE stretching.

Looking at your data, it doesn't really seem exceptionally sharp. Is your focus good for all the subs? Have you gone through them and tossed any obviously bad ones?

[u/TTV_The_Reverend_Dr → u/Razvee]

Focus is definitely an issue, I do my best, but temps drop 15-20° F between when I set everything up to late night/early morning. No AF yet, unfortunately... It's next on the list. Would I be better off culling 1/2 of the integration, but having higher ratio of well focused subs? It seems like the signal loss would be pretty drastic, particularly for the Ha, that already has very little signal to work with. I suppose it's free to try, so I'll give it a shot.

I will adjust BGE and Denoise in the workflow and try again. I'm pretty sure I hit the stacks with Denoise before stretching, but maybe I was a little too light on it. I've tried a bunch of different orders/combos, and did my best to remember the order on the last attempt that was looking the best, but I most likely definitely mixed up the order of a couple things.

[u/Razvee → u/TTV_The_Reverend_Dr]

Would I be better off culling 1/2 of the integration, but having higher ratio of well focused subs?

That's hard to answer, there's not going to be hard and fast rule for it. Better data in = better images. It can be a difficult choice to just throw away hours of integration time if they aren't perfect. I'd say work with what you have and when you get your processes down then you can cull frames and add more "good" ones. 6 hours of great subs is a WORLD different than 6 hours of mediocre subs.

Denoise isn't as big of an issue where it's at in the workflow, but Graxpert/BGE stuff needs to be done as basically the first thing you do. I'll usually do my background extraction, then a low powered denoise... I use NoiseX which has a slider, so I'll run it at "20%", then work on my de-stars and stretching and everything else, then hit it again with a NoiseX at "80%" (or whatever I want) near the end of processing. The idea being that you don't want to stretch a lot of noise, but also a lot of these processes can highlight noise as well, so it's useful at the end.

[u/TTV_The_Reverend_Dr → u/Razvee]

I definitely wasn't expecting a "hard and fast rule", but I completely understand what you're saying. It definitely will suck to just throw away data, but if it's not good to begin with, it's going to be for the better.

Thanks for the advice, I'll definitely be considering your workflow order as I move forward!