Excalibrated Cat.

[alocky (Andrew lockwood)]

After following with some interest the other threads on this object I had another go at processing it using Excalibrator to determine the correct channel balance. I also used the NBRGBCombination script to addd the H-alpha, and it seemed to reduce the salmon effect considerably.
What's interesting is how weak the blue and green subs are in comparison to the red, according to Excalibrator; the blue channel weights are nearly double the red, although the integration times are both 60 minutes worth.
I've also got a very wide field of the Sag-Scorpio region taken with the unmodded D800 a year ago, and both this object and the Lobster show up as very dark red, whereas the eagle, swan lagoon and trifid all are quite pinkish in comparison - http://www.astrobin.com/46578/
Anyway, if I've any hope of showing up some of the subtle blues in here, it looks like I'll need another couple of hours of blue. If only it would stop bloody raining!!!
Comments welcomed.
H-res version on flickr:
https://www.flickr.com/photos/photon...r/14398662277/
cheers,
Andrew.

[strongmanmike (Michael)]

Yep...red it is

The shade of red is the issue and whether any other subtle hues can be revealed. I have seen plenty of version like yours with more of an orange tint and little or no colour variation but there is colour there and selective processing and some decent amount of RGB data is probably necessary to really show it.

Nice work Andrew

Mike

[alocky (Andrew lockwood)]

Originally Posted by strongmanmike

Yep...red it is

The shade of red is the issue and whether any other subtle hues can be revealed. I have seen plenty of version like yours with more of an orange tint and little or no colour variation but there is colour there and selective processing and some decent amount of RGB data is probably necessary to really show it.

Nice work Andrew

Mike

Thanks Mike - There's definitely some signal in the blue channel, but in my data at least it's a lot harder to get out than the red! There's a lot more interstellar dust in the line of sight, which is presumably why it appears more blood-red than the other HII regions nearby.
Assuming the actual source of the light is dominantly H-alpha emission, we know exactly what colour it is, right?
cheers!
Andrew.

[strongmanmike (Michael)]

Originally Posted by alocky

Thanks Mike - There's definitely some signal in the blue channel, but in my data at least it's a lot harder to get out than the red! There's a lot more interstellar dust in the line of sight, which is presumably why it appears more blood-red than the other HII regions nearby.
Assuming the actual source of the light is dominantly H-alpha emission, we know exactly what colour it is, right?
cheers!
Andrew.

Yep deep red actually nearby NGC 3576 is also almost uniformly very red for the same reasons...but really in the end it is like interior decorating ie all about taste and often preconceived ideas about how the room should look

T'is what makes this passion so interesting

Mike

[Peter Ward]

Very impressive needle-like stars. Smooth as.

[gregbradley]

Lovely image. What gear did you use?

Greg.

[alocky (Andrew lockwood)]

Thanks Greg and Peter!
Scope is an old Meade Starfinder 10" F4.5 with a Rowe corrector, camera is a QSI 683wsg-8, mount is a G11 with Gemini2. All channels were 6x10 minute subs except Ha which was 15.
I used SGPro with autofocus every 30 min for data capture and Pixinisght for processing. Guiding was PHD2 with and a lodestar.
cheers,
Andrew