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Sh2-124... too difficult!

ollypenrice

By ollypenrice
in Imaging - Deep Sky

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ollypenrice

ollypenrice

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What's the hardest kind of target? In my opinion, a faint and diffuse Ha nebula with little signal in other wavelengths, in a dense Milky Way starfield, imaged in natural colour plus Ha. Our recent guest Gordon decided to take this on! Why is it difficult? 1) the broadband stars easily overwhelm the image if given a chance. They have to be kept down and made to behave... 2) the main interest in the image, the Ha nebula, is by nature monochromatic and therefore colour-flat. In this rendition I allowed a bit of the brighter Ha signal into the blue channel as surrogate H beta in order to get some colour contrast for the small circular main nebula cut by the dust lane. Jut a whiff, you understand. I don't want to be hauled before the DS imaging Thought Police... Well, that's a lot of excuses for one picture...

Dual Tak FSQ106 rig, twin Atik 11000 CCDs, Mesu 200, Ha RGB. (We did shoot some luminance but after using it on a first attempt I didn't use it on my keep those stars down verion here. Done in a single night. About 10 hours data all in.

Sh2-124%20HaRGB-XL.jpg

Olly and Gordon.

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ollypenrice

ollypenrice

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By the way, Gordon and I were delighted that two of the three bright stars framing the nebula in a triangle turned out to be blue. We'd been praying for this and did a quick colour test while imaging to find out. The image really needs that relief from the reds.

Olly

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ollypenrice

ollypenrice

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16 minutes ago, gorann said:

Very nice Olly & Gordon!

I agree about the blue stars making it all more pleasing. I just would like to know what a quick colour test is? Sounds useful.

Once we had one sub of each colour we quickly combined them in AstroArt on one of the image control PCs (one for each scope for the Tandem Tak) to see what colour the stars were. Blue was great news!

Olly

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ollypenrice

ollypenrice

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I still wasn't happy with the stars so this time I did a heavily star-masked stretch of the luminance and added it to the RGB. (The version above was without luminance.) This gave the smallest, tightest stars to date so then the Ha went back in the red to give this...

Sh2-124%20HaLRGB%20web-L.jpg

Olly

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swag72

swag72

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Sometimes it's annoying and frustrating to accept that there are some targets that don't don't seem to want to display their beauty in the normal way..... I have to say that this target for me was exactly this, I tackled it a few years ago in narrowband and ended up with something less than average.....

In your image I like that you have managed to be able separate the main target from the surrounding nebulosity and in the second I really like the star field...... I think that the overall colour is bothering me...... is it too saturated? I'm not quite sure and neither can I put my finger on it quite yet. Originally I thought it was too pink, and so found your Simeis 147 image that I always have in mind as a lovely red and compared them..... You're not a million miles from that colour.... so I'm not sure what it is that I can't pinpoint. I will keep coming back to it :) 

** I've had a little play and I'm happy to send you what I've done.....I think that the background is too magenta and making that slightly more neutral, while still maintaining the red seems to work well to my eyes**

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ollypenrice

ollypenrice

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1 hour ago, swag72 said:

Sometimes it's annoying and frustrating to accept that there are some targets that don't don't seem to want to display their beauty in the normal way..... I have to say that this target for me was exactly this, I tackled it a few years ago in narrowband and ended up with something less than average.....

In your image I like that you have managed to be able separate the main target from the surrounding nebulosity and in the second I really like the star field...... I think that the overall colour is bothering me...... is it too saturated? I'm not quite sure and neither can I put my finger on it quite yet. Originally I thought it was too pink, and so found your Simeis 147 image that I always have in mind as a lovely red and compared them..... You're not a million miles from that colour.... so I'm not sure what it is that I can't pinpoint. I will keep coming back to it :) 

** I've had a little play and I'm happy to send you what I've done.....I think that the background is too magenta and making that slightly more neutral, while still maintaining the red seems to work well to my eyes**

Send away! Thanks for the input. I can Dropbox you the TIFF if you like.

I measure the background to be high in red with green and blue at parity. In version two, as in V1, I added some Ha to blue as surrogate Ha but re-curved it so it only affected the brightest parts of the nebula. This helps isolate the small round main component with a slight colour change. I've just tried bringing in the black point in red and there's something to be said for it - though there is, in truth, faint Ha right across the field.

I do tend to have high colour saturation, this coming in for more comments on the French forum than here. Maybe it is a bit high!

If I bring in the black point in red to clip the faintest Ha, lift the background to about 23/23/23 and lower the saturation in red we get this:

597f5e245dfaf_Sh2-124HaLRGBalternative..thumb.jpg.3389a0871b5a20c46b2397f5fa2581e4.jpg

 

Olly

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pietervdv

pietervdv

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Very nice, the h-alpha layer goes very deep. I like the "natural" combination of h-alpha with RGB data here, somehow a hubble palette always looks "forced" to me (if that makes sense ... :happy10:).

I like this target, should try it myself if the endless clouds ever disappear around here.

Regards,

Pieter

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Tom OD

Tom OD

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Don't know this  object at all. Its weird with the Pinker central part. I like it and the central dark dust lane, but it is very red, and I understand the difficulty in processing this. Tricky one. Does further addition of the L layer help tame the Red, despite what it does to the stars in the blend?

Tom

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ollypenrice

ollypenrice

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9 minutes ago, Tom OD said:

Don't know this  object at all. Its weird with the Pinker central part. I like it and the central dark dust lane, but it is very red, and I understand the difficulty in processing this. Tricky one. Does further addition of the L layer help tame the Red, despite what it does to the stars in the blend?

Tom

The pinker central part is down to my addition of the brighter Ha to blue. It's a bit of a cheat to break the colour monotony!

The saturation is still quite high and could easily be eased down.

Olly

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