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Old 01-09-2020, 11:51 AM
Startrek (Martin)
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A quick Tuc 47 with the ZWOASI2600MC

Ive imaged a stack of globular clusters over last 3 to 4 years with my newts and Canon 600D which produced good results but this is the first time using my new OSC ZWOASI2600MC
On Sunday night the moon was 80% lit overhead so used the Duoband filter
6Ē f6 newt on an EQ6-R mount
ZWOASI2600MC with Baader coma corrector and ZWO 2Ē Duoband filter
40 x 60 sec dithered guided subs
15 x darks
15 x flats ( 20,000 ADU )
Camera cooled to -2C
PHD2 guiding was atrocious at 1.50 to 1.60 arc sec
Goto and tracking EQMOD ,StellariumScope and Stellarium
Frame , Focus and Capture APT
Stacked in DSS
Processed in Startools V 1.5 Linear OSC

Comments Welcome

Since using the new 2600MC camera over the past 3 weeks Iíve noticed when I start to use the colour module towards the end of my workflow , the object and stars tended to have a greenish cast whereas when using the old Canon 600D DSLR the object at the commencement of the colour module was more neutral. Both cameras have an RGGB Bayer matrix
Any explanations ???
Thanks
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Old 01-09-2020, 02:06 PM
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PKay (Peter)
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Hi M.

Just to give you an idea of how good this image is,

I am comparing it to an image taken by data obtained with FORS1 on Kueyen,
UT2 (Very Large Telescope).

Yes there is a difference in resolution.
They zoomed in to the core to 7 arc min. wide.

And the stars have a different hue.
They used NB, you used a OSC.

Who knows who is right, maybe you both are.

Hidden in your image is a few red giants.
By playing with the curves, you could well find them.


Well done mate.
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Old 01-09-2020, 02:14 PM
raymo
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Yes, good job Martin.
Peter, I have noticed that the star colour in Martin's globulars is always a sort
of mauve, which is a colour I have not seen in other images. I imagine that
Martin must do something different during processing. Perhaps he will tell us.
raymo
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Old 01-09-2020, 02:42 PM
Startrek (Martin)
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Peter
Thanks for the humbling reply
I might also add that Iím imaging at 900mm fl with my 6Ē newt at an image scale of 0.86 arc sec per pixel. Seeing was terrible that night , moon washing out everything , guide star fading in and out , PHD2 HFD numbers jumping up and down like the stock exchange , neighbours flood lights on both sides ( 2 storey brick mansions ) my Sydney location sits in a low gulley , smoke from chimney 2 doors up wafting towards my place Hmm .....what else is against me
I need to get back down south !!!

Raymo
These globs tend to have a background core area with a greenish tinge which I hate , so I try to bump up red and blue to reduce it and I tend to push that too far and it ends up a bit bluish mauve
Actually I donít mind it , better than a green bias or plain mono

Cheers
Martin
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Old 01-09-2020, 03:01 PM
Startrek (Martin)
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Peter
I forgot to mention , thereís no levels and curves or DBE in Startools
Have a look at a trial version
Itís really easy to use and great for noisy data, cleans it up beautifully
Itís definitely come a long way from the early versions years ago , Iím running v1.5 and the latest is v1.6 which has a load of features for narrowband etc...
Martin
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Old 01-09-2020, 03:09 PM
raymo
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Martin, I am intrigued by this colour thing. I have never noticed any sign of
a green cast in globs. Of course, everyone perceives colours differently, and
to different degrees. I, being limited to DSS, always accurately equalise the three colour cones so that the end result is as close as possible to what our eyes would see, and no colour cast presents itself. I don't have a decent
47Tuc, but my next oldies' image happens to be O.Cent. I welcome your
thoughts on the colours in the image.
cheers raymo
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Old 01-09-2020, 03:42 PM
Startrek (Martin)
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Raymo

Thanks Iíll look out for your OC
I use DSS too but only to stack , my stacked image is left pure linear not tweaked at all as Startools require clean linear data to allow it to maximise processing opportunities and maximise the dynamics of the captured data

Being in suburban Bortle 8 Sydney ( population 5.3 million ) with both light and air pollution, Startools is a real life saver when it comes to removing gradients and associated noise and extracting useful data

Cheers
Martin
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Old 01-09-2020, 03:49 PM
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Fantastic image Martin.

I cant comment on colour as I am colour blind ... It looks very blue to me..Apparently I dont see red like other people do.

Why dont you download Gimp..you have levels there and Hue and Saturation tool which should give you additional colour control , its useful for little adjustments.. plus has dodge and burn...hey Raymo you should down load it and you will have a dodge and burn that you liked...I dont know how it fits in comparison to film but thats what they call it.

I think dodge and burn are fantastic tools ... Takes a while to not overdo it but I think it really helps.

The new Gimp is apparently as good as Photoshop for most purposes and unlike Photoshop, Gimp is free...also there are excellent tutorials on you tube.

It has a layers set up which really helps when processing...I often end up with two final images which each seem to have their individual qualities that you like...so put them in layers and using the rubber tool you let in the best from whatever image is on the bottom. Or (cheating) if you have high noise in the background make a dark image where it disappears in the darkness put it over your image and using the rubber just bring out the object...works sometimes.
Alex
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Old 01-09-2020, 06:18 PM
raymo
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Thanks for the suggestion Alex, but it is a little late. I rarely venture out into the night with my camera now. My little tracker just sits there looking all forlorn.
raymo
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Old 01-09-2020, 08:04 PM
etill (Elliot)
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I see the mauve color in that one too, but I also regularly use different monitors and things can look very different for the same images. There's a chance the image looks different to different people due to the monitor more than the image. My mac retina screen is significantly different to the regular asus monitor I use with my linux workstation.
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Old 01-09-2020, 08:27 PM
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Sunfish (Ray)
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Pretty crisp round stars which does not happen much with those clusters.

My experience with a DSLR and no filtering is that the they tend to be mostly blue and yellow stars. The Blue Stragglers apparently and older yellow, brighter and low metal stars. Less red maybe?
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Old 02-09-2020, 07:27 AM
Startrek (Martin)
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Thanks Alex Elliot and Ray
Always good to receive comments
Iím still learning with this new camera and colour is one of the challenges
Thanks again
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Old 04-09-2020, 12:20 PM
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The_bluester (Paul)
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Regards the colour, I have found a green cast to be "Normal" in the initial integration with an OSC astro cam (Based on the two OSC cameras I have had) Coming from a DLSR in your case before the ASI2600, might it have been applying a white balance adjustment to your files?

I use Astro Pixel Processor and ignore the green cast initially. There is a workflow step in APP for colour images (Background calibration) which balances the colours based on at least four image areas you select as containing "Background", the aim of which is to get the background areas to be a grey shade. Before that calibration step the images are normally quite green. I found the same thing when I was using DSS and tweaked the colour levels like you probably do to pull it back.

Nice 47 Tuc too!

Last edited by The_bluester; 04-09-2020 at 08:23 PM.
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Old 05-09-2020, 06:50 AM
Startrek (Martin)
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Thanks Paul
Yes Iím not use to the green cast with this camera , the DSLRís white balance was set to auto as recommended by Jerry Lodriguss (astropix)
With the new 2600MC after stacking in DSS Iím left with an almost black screen showing maybe 2 or 3 stars but this ok because my processing software Startools requires pure linear data ( untouched and not tweaked) from the stacker
Also when I check my star count in the Star Detection Threshold of DSS Iím finding that due to the new camera producing Fits files ( not Raw files like the Canon ) the star count is very low ( 15 to 50 ) even set at 2% , whereas using the DSLR the Star count was +300 set at 50% , Iím slowly getting use to this
Thanks again, itís great to share details about the new 2600MC camera
Cheers
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Old 05-09-2020, 07:10 AM
Startrek (Martin)
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Paul
A quick question if I may , have you been using 1x1 binning or 2x2 binning when imaging ?
Iíve read you should be imaging 1x1 binning with the 2600MC camera

NB: My processing software Startools has a bin module and I Bin 50% which is similar to a 2x2 bin

Your thoughts ?
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Old 05-09-2020, 12:00 PM
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The_bluester (Paul)
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I always shoot at 1x1 binning, I only bin 2x2 for focus or plate solving.



Regards the number of stars, APP presumably stretches the data as required for the registration module as it targets 500 stars for registration by default and always seems to hover around 490-510 in practice.
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Old 05-09-2020, 10:19 PM
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Some lovely resolution in that image. I won't comment specifically on the colour because I'm viewing on a cheap screen but it's interesting to hear what others get with their cameras. When it comes to globs my cameras tend to pick up the yellows in stars (highlights) and more blue in the background (shadows). Does that then make it green bias? I don't know but that's what I tend to get. Once I neutralise the cast then everything balances out with a nice mix of hot and cold stars. Great work and congrats on th new camera. It finally made it!
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Old 06-09-2020, 08:47 AM
Startrek (Martin)
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Thanks LIS
Still so much experimenting and learning with this new camera but Iím starting to get a sniff of its capabilities and performance, so glad I chose this one !!
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