Colour NGC104_ now with repro.

[Bart]

Finally got some colour for my NGC104 image, with NGC121 getting a look in as well. Two globs in two galaxies! Not very much data or not as much as I wanted although for now it will have to do. Still struggling with focus, will try to get out under the moon and nail the Temp Compensation and see how that goes.

Details


Telescope: William Optics FLT132

Guide Scope: QHY OAG

Camera: QHY9 Mono @ -20c

Filter Wheel: QHY 7 position Ultra Slim

Filters: QHY 36mm unmounted L R G B HA OIII SII

Guide Camera: QHY5L-II

Mount: AZ-EQ6

Mount Control: EQASCOM

Focusing: SharpSky Pro and Sequence Generator Pro 3 (automated)

Bahtinov Mask: No

Capture Software: Sequence Generator Pro 3

Guiding Software: PHD2

Calibration and Stacking Software: PixInsight

Processing Software: PixInsight

Number and Type of Data Frames: L= 19X300 sec, L =7X120 sec, L= 14x30 sec, R= 10x180 sec, G= 10x180 sec, B= 10x180 sec

Ha= x , SII= x , OIII= x .

Binning: 1x1

Total Image Time: 206 minutes

Location: Lockleys Observatory B, Tanunda, Sth Australia

Light Box by Exfso

Full Res

http://www.pbase.com/image/168197638 (http://www.pbase.com/grahammeyer/image/168197638/original.jpg)


Reprocessed image can be found here. Thoughts appreciated and thank you to Mike and Trish and Paul Haese for there input.


http://www.pbase.com/grahammeyer/image/168299434

[gregbradley]

That turned out very well.

With temp compensation I found keeping a log of the temperature and the focus positions and then working out an average number for the shift of focus/ degree C worked pretty well. It does assume focus shifts are linear and they probably are initially then they flatten off (I think or at least they seem to with my scope). Most likely due to a closing of the difference between ambient and the temp of the objective.


For example my CDK17, when the temp difference is more than 1C it will not be spot on focus but once its within .5C it reaches a peak and focus is sharp.

Greg.

[Placidus]

Looking very fine Bart.

Just looking at the numbers, the background has quite a blue cast, but even if I fix that, the glob is slightly too blue. Although globulars contain a smattering of very salient blue stars due to mergers, globulars, with their extreme age of around 10 billion years, cannot on average be blue, because blue stars are so hot they only live a million years or so.

Despite that minor quibble, a lovely image.

Best,
Mike

[Bart]

Thanks for taking a look, people. :thumbsup:



Interesting feedback, Mike and Trish. I will have another look at it and check my colour calibration. :question:

[RickS]

I'd agree with M&T on the need for a slight colour tweak but very nice, nonetheless :thumbsup:

[Atmos]

You've achieved better colour differentiation/separation than what I have in the stars which is good :thumbsup:
Resolution is good but you've got the same problem that I did with an overly bright core (it is a very bright core mind you).

Very nice globular though :)

[Bart]

Thanks Rick and Colin for the feedback. I did leave the core bright as I think it looks a bit more natural rather than trying to dull it out.

[Atmos]

You are correct, it can look better not making the image flat :thumbsup:

[Paul Haese]

Resolution looks good Gray. I agree with the comments about the blue background cast. The histogram has blue to the right of the mid point. As Mike said, the cluster has mainly old main sequence stars and a smattering of blue stragglers. If you adjust the blue, the bulk of the stars looks white with notable blue stragglers and a few orange giants. Back ground comes up charcoal then.

[DiscoDuck]

Lovely image, Bart.

Nice with NGC 121 in the frame too.

[John Hothersall]

This one has a tough dense core which has come out pretty well.

John.

[Bart]

Thanks for the feedback and comments, I really appreciate it. :thumbsup:

Working on a less blue repro. :)

[ngcles]

Hi Paul, Bart & All,

First up, very, very nice image Bart. Congratulations.



The thing that one has to bear in mind about "blue straggler" is that they are blue in a comparative sense and very rarely if ever actually "blue" -- ie have a B-V trace in the negatives. Most blue stragglers are currently believed to be merger remnant stars that are the result of two smaller stars colliding and/or merging or as a result of mass-transfer in a tight binary system. While stellar collisions/mergers are a vastly improbable event among the general population of stars in our galaxy, it is unlikely but does happen within the very, very dense cores of globular clusters and even in some dense open clusters where the distance between individual stars can be measured in light-hours as opposed to light-years.

Typically blue stragglers are F-type or at best very late A-type stars with a mass between 1 and 1.6 solar masses. The turn-off point (from the main sequence) for most genuine G.Cs is in the mid to late G-type (ie about 0.8 solar-masses). As I said, blue stragglers are generally not genuinely blue, but comparatively blue and anomalously blue when compared to the other brighter member stars in the cluster (that are typically red AGB-tip stars). I would think that proper processing would render most of, if not nearly all these stragglers as white or very light yellow as opposed to blue. There might be a very few actually blue stars in a typical G.C that are, in the main, horizontal branch post AGB stars (and probably RR Lyrae-type variables) powered largely by the triple alpha process.

Best,

L.

[Bart]

Wow, great info, Les. Thank you! :thumbsup:

[topheart]

Lovely!
Cheers,
Tim

[Placidus]

Bart, the background is now excellent. and the cluster is hugely improved.

An evil rotten purist might suggest just a tiny bit (I measure 6 percent) more red. But that would be missing the point. It is now a superb image.

The detail in the core and the handling of the relationship between the core and the outer reaches is particularly good.

The level of saturation is pleasing, enough to see what is going on, and is supported by the amount of data.

Best,
Mike

[Bart]

Thanks for looking Tim! Glad you liked it! :)


Mike, thank you for your input and advise, as well as Paul Haese and every one else, I think it says a lot about the IIS community. :thumbsup:


PS: Red mode engaged!:lol: