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Missing HA in my Triangulum galaxy?


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Hi,

I've just finished processing some data I got on the Triangulum galaxy over January, but despite my best efforts I can't seem to draw out much HA. See below. I'm using SPCC and GHS within PI, and although very much a beginner still I can find my way round a number of the processes. This one was dynamic crop, DBE, SPCC, BXT, NXT, Starnet 2, GHS (starless), LHE (Starless), GHS (stars), Pixelmath to recombine. I've had 3 or 4 goes at it now and this is the best I have done so far, but would still expect to see more HA from my astro modified EOS 600D and 130PDS. If I look closely I can see hints of red throughout the spiral arms but not sure what I would need to do to draw that out without affecting colour balance. Its about 4hrs data, so do I need more maybe?
Any pointers gratefully received!

Thanks
Ed

Triangulum Galaxy 2023.jpg

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Can I assume if you are using a modified DSLR you have not specifically collected Ha data with a NB filter? If that is the case then all you can do is accentuate the red channel which contains the Ha signal, but as you say, avoid upsetting the overall colour balance, which looks good in your image.

M33 is rich in Ha regions, but those images that show this clearly have usually had Ha data added into the LRGB.

Nice M33 BTW, more integration will help as well as reveal the faint outer regions.

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Thanks Tomato, and no I'm not using an NB filter, only just recently ditched my CLS filter in order to grab more photons per hour. Something I don't understand with NB filters though, hopefully you can help.....if I can explain myself correctly lol.
So I've collected 4hrs of data here, that should include 4hrs of HA as well presumably. So how do NB filters help above and beyond just getting more integration time in LRGB? (clearly they do - I just don't understand). Its not that they can somehow boost HA collection, just isolate that and reject other wavelengths? So how does that help more than just getting more RGB?

I guess what I'm asking is how does gathering more HA specifically help more than gathering more LRGB which should include HA anyway?

Thanks
Ed

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24 minutes ago, edarter said:

I guess what I'm asking is how does gathering more HA specifically help more than gathering more LRGB which should include HA anyway?

What Ha you are getting with the R filter is actually HA + light polition, the light polution is much reduced with the Ha filter and so you get much higher signal to noise and scan stretch the specific Ha regions much harder then add them to the R channel.

Adam

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20 minutes ago, Adam J said:

What Ha you are getting with the R filter is actually HA + light polition, the light polution is much reduced with the Ha filter and so you get much higher signal to noise and scan stretch the specific Ha regions much harder then add them to the R channel.

Adam

ok, thanks Adam. Makes sense

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You have captured the brightest Ha regions already in ONLY 4 hours, so you are doing better than expected i would say. Even with astromodification the absolute QE of your 600D is still not that great in the deep reds.

More time put into the image and more Ha will show up. Some kind of narrowband filter would make adding just the Ha faster, but not contribute to the RGB data anymore, so its a compromise.

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Just thinking about this a bit more - is there anything I can do by splitting the channels and boosting red somehow? I know its a bit of a cheat but just curious as to what the possibilities are other than gathering HA data.

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13 minutes ago, ONIKKINEN said:

You have captured the brightest Ha regions already in ONLY 4 hours, so you are doing better than expected i would say. Even with astromodification the absolute QE of your 600D is still not that great in the deep reds.

More time put into the image and more Ha will show up. Some kind of narrowband filter would make adding just the Ha faster, but not contribute to the RGB data anymore, so its a compromise.

Yeah the more I think about it the more I realise that 4hrs is not that much actually (and that I need a dedicated astro cam lol!)

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5 minutes ago, edarter said:

Just thinking about this a bit more - is there anything I can do by splitting the channels and boosting red somehow? I know its a bit of a cheat but just curious as to what the possibilities are other than gathering HA data.

Would you be able to share the unprocessed stacked tiff? I could have a fiddle and see if an idea I have could work out for you

Your image looks very nice already though I must say!

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4 minutes ago, pipnina said:

Would you be able to share the unprocessed stacked tiff? I could have a fiddle and see if an idea I have could work out for you

Your image looks very nice already though I must say!

Happy to do that, though the file is rather large!
Thank you, I'm very happy with it, just never satisfied lol! Have finally come round to the idea that I really need to chop the focus tube on the 130PDS to get rid of those bl**dy  pacman stars! Something for this weekend maybe.

File can be found here(FITS rather than TIF, hope thats ok):
https://www.dropbox.com/s/amcmgxly9zgbtwf/Triangulum_Galaxy-session_1_session_2_session_3_session_4-NoSt.fits?dl=0

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1 hour ago, edarter said:

Happy to do that, though the file is rather large!
Thank you, I'm very happy with it, just never satisfied lol! Have finally come round to the idea that I really need to chop the focus tube on the 130PDS to get rid of those bl**dy  pacman stars! Something for this weekend maybe.

File can be found here(FITS rather than TIF, hope thats ok):
https://www.dropbox.com/s/amcmgxly9zgbtwf/Triangulum_Galaxy-session_1_session_2_session_3_session_4-NoSt.fits?dl=0

Sadly my idea didn't work 😕
I tried to reduce the larger detail levels int he galaxy so i could try and boost the areas where ha would be, but I couldn't isolate it much at all.

Also looking at what you started with, I can see you really know your way around editing your photos!  I was really struggling to get a background or colour anywhere as clean as yours.

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I had a play with a screen grab using a Photoshop trick which usually accentuates the Ha component in the red channel but, for once, it had little effect. I think your colour balance is a little cold - blue dominated - because M33 is pretty colour-neutral rather than blue, but it would seem that you may not be collecting much Ha signal as things stand.

Olly

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2 hours ago, pipnina said:

Sadly my idea didn't work 😕
I tried to reduce the larger detail levels int he galaxy so i could try and boost the areas where ha would be, but I couldn't isolate it much at all.

Also looking at what you started with, I can see you really know your way around editing your photos!  I was really struggling to get a background or colour anywhere as clean as yours.

Thanks, I tried something similar but it ended up as a horrible mess lol.

I'm sure others would do better with the processing but I do feel I'm improving with pixinsight. The generalised hyperbolic stretch has become my new friend with regard to preserving colour during stretching.

Ed

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1 hour ago, ollypenrice said:

I had a play with a screen grab using a Photoshop trick which usually accentuates the Ha component in the red channel but, for once, it had little effect. I think your colour balance is a little cold - blue dominated - because M33 is pretty colour-neutral rather than blue, but it would seem that you may not be collecting much Ha signal as things stand.

Olly

Thanks for trying Olly. Interesting comment about it being a bit cold. I've kind of taken spcc as gospel once applied and tried to stay true to that. The stars were on the money regarding following the expected plot lines, maybe I should try tweaking it a bit more and see what happens.

Ed

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