M31 Andromeda Galaxy [Ha]LRGB reprocess

[ChrisLX200]

Well I wasn't happy with the last process, the core rather got away from me and was blown out. There was no simple way to correct that by messing with the final image so I re-processed the lot again. Turned out a bit better but I always have a problem generating a star mask which includes small stars embedded in a bright background (like the stars around the bright core). As a result these often end up with unsightly halos. I need to work on that.

Full res image available here, click the (+) button top-right of the picture. http://s970.photobucket.com/user/ChrisLX200/media/Astro - Images G4-16000/M31 HaLRGB_zps3y5rrpid.jpg.html

ChrisH

[PatrickGilliland]

Thats superb Chris well done.  Super detail without looking pushed at all.  That NB data paid of very well.  The tome is great feels very 'alive' 

Paddy

[Knighty2112]

Excellent image. Well done!  

[ChrisLX200]

52 minutes ago, PatrickGilliland said:

Thats superb Chris well done.  Super detail without looking pushed at all.  That NB data paid of very well.  The tome is great feels very 'alive' 

Paddy

Many thanks Paddy, I think maybe the Ha is a bit 'in your face' and possibly a too pink but I don't have a good consistent method of combining Ha yet. Currently using NBRGBCombination script in PI

28 minutes ago, Knighty2112 said:

Excellent image. Well done!  

Cheers Knighty, appreciated!

ChrisH

[PatrickGilliland]

5 minutes ago, ChrisLX200 said:

Many thanks Paddy, I think maybe the Ha is a bit 'in your face' and possibly a too pink but I don't have a good consistent method of combining Ha yet. Currently using NBRGBCombination script in PI

Cheers Knighty, appreciated!

ChrisH

I do it manually - start blend (.75R +.25(sii(.76) and ha(.24)), .75G+.25(ha*.85+sii8.15) and 0.75b+(.25oiii), then i take a look and start tweaking.   Find that more flexible and provide you options based on the data you have.  Can reinforce with NB as much or little as you want then.  But then sometimes i extract the lum from a single channel and apply as a lum layer to the NB weighted as required all options viable.  Having a play with combo's I have found to be better than scripts (most of the time)

Paddy

[alan4908]

1 hour ago, ChrisLX200 said:

I don't have a good consistent method of combining Ha yet.

A great image Chris !

For Ha combination into RGB I'm currently following the suggestion by Adam Block that was explained in his cosmic canvas video tutorial:  before any colour enhancement take the LRGB image and split into separate channels. Create scaled images of each channel (eg permanently stretched images). Take the H channel and create a scaled image. Significantly black clip the scaled H channel to eliminate the background contribution and use the Screen PS blending mode function with the red scaled channel to produce a red blended channel, call this R(Blend). Reduce the opacity on the H channel to taste (eg 25% to 50%).  Take the R(blend), G(scaled), B(scaled) images and recombine into RGB.   Apparently, the reason you create the scaled images is to minimize the introduction of colour imbalance created by the introduction of the Ha signal. A similar procedure can be followed with the L channel after deconvolution, so here you end up with L(blend) = L(scaled) + Ha (black clipped, opacity reduced). Given that the PS screen blending function is simply additive, I presume you follow the same process in Pixinsight but I haven't tried it yet.

Alan

[StargeezerTim]

Superb image. Fabulous colours and detail.

I'm no expert but it might be worth making a star mask just for the stars with bright background. I've found the same as you? Most are ok but you get halos around some. I think they need treating separately. Do as i say, not as i do! 

[carastro]

Excellent work Chris and lovely image.  I do agree that the Ha bits are a bit too Pink/in your face and I too have trouble combining the Ha into data.

I worked out a system for myself in Photoshop if this is any use, depending on whether you use photoshop.  This sometimes works like a dream, and sometimes it doesn't and needs some fiddling:

Convert Ha to RGB mode then put the RGB image over the top of the Ha image in layers and combining as blend mode "lighten"  I switch off the upper layer (RGB) and increase the red in the Ha layer in curves (first anchoring down the Black and white points).  Switch on the RGB later again and the Ha "highlights" should show through. 

You can tweak the opacity - to show a bit more without altering the overall RGB colour too much. somewhere around 75 - 85%.

Carole 

[ChrisLX200]

Thanks Alan, Tim and Carole! Some great suggestions to try out

ChrisH

[Rodd]

Nice image--clear as a bell.  Is that a slight greenish tinge I see?  Or maybe that's blue and I am getting old.  Don't see the halos you mention.  Looks good.  One thing Vicent Peris taught us, is that there is red frequency in the Ha data, so you have to "clean" the Ha (use pixel math to remove the red sky background from the Ha before inserting the Ha into the Red channel).  Also, there is Ha emission in the Lum channel, so a clean Ha mask is made and applied to the extracted lum channel, and the clean Ha is inserted into the Lum channel (only in those areas where the Ha is located and exposed  by the clean Ha mask)before the Lum is reinserted into the mix.  Anyway--we learned the procedure at the seminar and I thought I would pass it on in case you did not know it.  

[ChrisLX200]

Thanks Rodd, always looking for ways to improve!  No green should be visible in the image (100% SCNR Green done on it!) so it's likely your monitor

ChrisH

[toxic]

well its awesome Chris but what i like most about it is the area around the core looks like a bowl shaped gravity well  with 2 arms getting sucked in i have not seen this on any m31 before.

[ChrisLX200]

Thanks Chris, takes imagination

ChrisH

[gnomus]

Very nice.

[Mr Spock]

Looks great - very smooth and detailed. The Ha is a bit strong though, spoiling the overall look.

[Pompey Monkey]

Very nice Chris!

I am still getting used to PI (and any processing for that matter!)  I have just combined Ha with the red channel  of and LRGB M31 using "max(Ha,LRGB_R)" and then recombining the channels. It's subtle, but seems to work well - although I do now have a rather pinkish core...

[ChrisLX200]

14 minutes ago, Pompey Monkey said:

Very nice Chris!

I am still getting used to PI (and any processing for that matter!)  I have just combined Ha with the red channel  of and LRGB M31 using "max(Ha,LRGB_R)" and then recombining the channels. It's subtle, but seems to work well - although I do now have a rather pinkish core...

Yes I got that pink core repeatedly, in the end I took the Ha channel and masked the core off (in PhotoShop ) then simply dimmed it! 

This is the problem when you have two equally capable processing programs to choose from, I'm sure if I only had one or the other I would be able to concentrate on using/mastering just that program - as it is I'm useless with both!

ChrisH