Bubble Nebula slightly wider field

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Bubble-Claw_AlpT+OSC_v2_1600x1054_500k.jpg (476.14 KiB) Viewed 5670 times

No astrobin link yet, not until y'all weigh in on how it could be improved

A bit wider field compared to Stefan's (and somehow inverted - what is the correct orientation???)
The field is that of an AT65EQD tossing photons against an IMX571C sensor. 16 3/4 hours with the Antlia AlpT filter and just under 2 hours without.
I did not push the nebulosity nearly as hard as Stephan did.

There is one round of 80% dimsmall and one mild shrink (2 iterations). Mike?

Continuing learning to add OSC star colors to duoband data. The two open clusters, especially, are way to pretty to leave as clunky duoband stars. A lot of neat stuff in here beyond the Bubble and the Lobster Claw. The lower-left cluster is M52, the top-center one is NGC 7510 (Stellarium lists "Arrowhead Cluster" as a secondary name, but I like that better than "Dormouse Cluster"). The Northern Lagoon Nebula NGC 7538 is the very bright nebula upper-left, and Stellarium calls the knot of Ha right between the Lagoon, Claw and Bubble SH 2-159 / LBN 543 and descrobes it as a "young stellar object". I'll try to look up more about that.

[Mike in Rancho]

Yes, a little bit different take than Stefan's, but very cool in its own right.

I tried this target (maybe 4 hours) last December not long after picking up the Newt, with the D5300 and L-eNhance. It was awful.

The region is just loaded with big and small goodies. I'm not sure there's a right-way-up. No spiral galaxy that we want a leading edge down for. As far as I can tell, everything is oriented to each other "correctly," and not mirrored either axis.

There's a bit of chop, which might be the region itself? You do have a good amount of integration.

What's the name of that small but super bright spot in the claw? I think I remember talking about that on CN a bit ago.

Star sizes look good. As you say, 2x iterations of shrink and SS 80% will be kind of mild. I see a good range of star sizes from tiny to medium to bigger, so nothing seems out of balance. And the colors are nice.

I did have to look up that other little knot of red towards the upper right just above the claw's, um, wrist? Didn't find a designation, but it just barely shows up in the digital sky survey. So...it's real. Yay!

Which brings me to the only critique of sorts, or question, that I have. Just up and left from that little knot, something doesn't seem right with the star V Cass. Unless it's just me? Though throughout the image the red stars seem a fair bit softer-cored than the blue ones, but that one seems to stand out more.

[Stefan B]

Looks really cool to me, it's one of those wide fields with the claw I had in mind when writing my post

I guess our images are not inverted, yours is just rotated 90° counter clockwise compared to mine I guess. Thus, either orientation should be fine.

Regards
Stefan

[dx_ron]

Thanks, guys!

Stefan - I must have been tired when I compared the orientations. Yes, just rotated not flipped.

Mike - I'm not sure which star you mean. v Cass is nowhere near here.
I normally try to follow Ivo's Dictum that you should color balance without touching Cap Green, which usually means bumping the bias against green way up until virtually all of the green is gone from Max RGB view. I will go back to the OSC image and try simply accepting the balance from the star mask and capping green.

I haven't found any annotations yet that give a separate designation for the bright spot in the claw.

[Mike in Rancho]

Mike - I'm not sure which star you mean. v Cass is nowhere near here.

Am I lost in space, again? Ruh Roh.

V Cass near Claw.jpg (247.11 KiB) Viewed 5619 times

I normally try to follow Ivo's Dictum that you should color balance without touching Cap Green, which usually means bumping the bias against green way up until virtually all of the green is gone from Max RGB view. I will go back to the OSC image and try simply accepting the balance from the star mask and capping green.

Maybe it all falls into the "it depends" category. Are your star samples representative enough to fall into an average-to-white situation? Is there dust, or remnant color casting/flaws that could affect the sampling? And so on. I've found I have to be careful relying too much on Max RGB, as it can have me chasing my tail. Too much green removal increases the relative red and blue, leading to purple, of course. And suddenly you start changing all three channels.

So I'll only start changing the green via the bias slider if it seems really out of balance, does not comport with good references, the stars don't quite match up with B-V values, etc. Huge chunks of green in Max RGB, especially if it is so strong as to also be noticeably to the eye in Normal mode (and of course if incorrect for the known target) -- then yeah the sampling didn't quite work out and needs help.

If full field sampling seems off, I wonder if a single star sample might work. If one has a clear shot at a known white reference star. I think Vega is considered the zero B-V point, meaning = 0.0, but is more like blue-tinted white to the eye. So something a little higher than that (and probabl not saturated like Vega would be). Maybe I'll try some experiments one of these days.

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Am I lost in space, again? Ruh Roh.

Oh - "V Cass", not "v (as in nu) Cass"

Hmm. Something went wrong with the layering there. Nothing gets by Mike...

Here's the stars:

r_172_pp-Bubble-Claw_OSC_with_NB_ref_500k.jpg (498.27 KiB) Viewed 5611 times

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Finally went back to this image to see what happened with/to V Cas, and I'm confused...

Here's a cropped screenshot from Layers:

V-Cas_Layers.jpg (203.79 KiB) Viewed 5502 times

V Cas, as Mike pointed out, has a B-V index of 1.3 and thus should be red. That's what's in the OSC version. In the duoband image, V Cas is oddly blue, though if it's red emissions do not include much right at 656nm the red would get filtered out. But it also has a diffuse blue surrounding that isn't seen in similarly bright stars with this AlpT filter. I expanded the mask to include all of the luminosity so as to not have V Cas as a weird red dot in the middle of a blue halo - and the result is the odd salmon color.

[Mike in Rancho]

Well, that is just pretty cool and weird. What are the odds? There'd have to be billions of stars out there for a funny coincidence like this.

V Cass is a pulsating variable, though what that really means as a practical and imaging matter I have no idea.

I have no data of my own here. I just checked the awful Bubble test I did, and I've only got the tips of the claw.

Theories....

How much Ha throttling was done on the duoband? When I mess with the Ha bias slider (R) on duo data it is fun to see more and more red stars turning blue. Though with an L-eNhance I probably start out more blue-shifted.

A google image search seems to show that this star can stick out in an odd way moderately often. So perhaps others have run into trouble too?

I'm leaning more towards issues with your RGB, though what? Unsure. V Cass seems both awfully tight, and awfully deep red. For its magnitude, one would think it should be a bit bigger than most of those blue stars nearby. Also, look at the red star at 8'oclock from V Cass, the one kind of surrounded by three blue stars like a hat above it. That's mag 9.5 and BV 1.52. V Cass is mag 8.75 and BV 1.30. Go figure.

And that's the RGB frame. So why would it process out that way? I'm baffled on that one, and can't be explained by the narrow passes of the duo filter.

So this scope is a quad? Or a triplet? I am confused by the description. Nonetheless, I guess I wouldn't expect blue bloating like a doublet.

How about focus? Could you have been slightly to the red side of things, pinpointing that more and leaving the blue side soft?

We need to get somebody in this thread who has some claw data we can examine in depth.

[dx_ron]

I will go back to the color module again and see what V Cas looks like with Red/Ha at full blast.

I have a theory on the salmon. With the mask expanded like I did, I originally thought the black background from the OSC image would be what blended in. But the black is due to pushing the luminance down. Telling Layers to use only the color info from the foreground layer will take whatever chrominance information (noise) happens to be there and make it the new color for the composite.

As for why V Cas is so strikingly red in the OSC - I have no idea. I get the occasional red star like that (there's one more way over on the left edge of this image). It might have something to do with how the Ekos autofocus routine works. I saw a post somwhere that they were implementing a switch to let you tell it which channel to use during autofocus (with the idea that you would probably choose green), but I don't think such a button or menu item has appeared yet.

The telescope, by the way, is a triplet objective with a 1-element reducer/flattener built in. Not exactly a Petzval, but Petzval-adjacent.

[dx_ron]

I've been kind of intrigued by the different look and feel between my image vs Stefan's, based on me using the duoband then only adding color from OSC using a star mask vs Stefan doing the primary processing on the OSC and adding the duoband with NBAccents.

My first try at processing that way was kind of underwhelming, at least in part because I have way more duoband time than OSC time. So I tried something different: I loaded the AlpT data as Luminance, the UV-IR cut as the colors, and the duoband again as NBAccents (is that a totally invalid approach?). This ended up with a look and feel much more like Stefan's image:

Bubble-Claw_OSC+accents-as-Lum_v1_500k.jpg (492.92 KiB) Viewed 5375 times

One impact is that all stars get their OSC color, while the star mask approach misses all of the smaller stars. But it also adds a weird color cast to the redder stars (and V Cas remains a problem child...).

There is a lot less definition to the nebulosity in the NBAccents version, but also the faintly nebulous regions get a more appropriate red tint, compared to a kind of distracting mottled bluish in the duoband-primary image (which is probably from trying to bring out bluish cast in the claw)