Orpington Astronomical Society

Astronomy => Astrophotography => Topic started by: MarkS on Feb 09, 2019, 18:18:16

Title: Horsehead 28/30 Jan
Post by: MarkS on Feb 09, 2019, 18:18:16
Horsehead Nebula.

Taken over two nights: 28/30 Jan.

This is 3.5 hours of data taken in 30sec subs.  Modified Sony A7S on Celestron C11 with Starizona LF 0.72x Flattener/Reducer.

(http://www.markshelley.co.uk/Astronomy/2019/Horsehead_20190130_small.jpg)

Full size version here:  http://www.markshelley.co.uk/Astronomy/2019/Horsehead_20190130.jpg

Altinak is out of control as always - the only way I could control the artifacts was to include the star just inside the frame during the shoot.

Mark
Title: Re: Horsehead 28/30 Jan
Post by: Carole on Feb 09, 2019, 20:31:59
Beautiful result Mark.  Lovely detail in  NGC2023, as well as some really nice dust and very little noise.

I'd say a real success.

Carole
Title: Re: Horsehead 28/30 Jan
Post by: RobertM on Feb 09, 2019, 22:04:33
That's really lovely Mark and I think that combination works really well.  I especially like the way NGC2023 looks like a three dimensional tunnel with excellent detail.

Robert
PS. Hope you've got over your bout of Flu.
Title: Re: Horsehead 28/30 Jan
Post by: JohnP on Feb 10, 2019, 11:23:34
Mark - that full size image is immense - very smooth result & superb detail - would look superb printed A3 or A2... John
Title: Re: Horsehead 28/30 Jan
Post by: Apophis on Feb 10, 2019, 11:45:01
Stunning image , Mark.
What was your processing train?
Roger
Title: Re: Horsehead 28/30 Jan
Post by: MarkS on Feb 10, 2019, 12:47:57
Quote from: Carole
Beautiful result Mark.  Lovely detail in  NGC2023, as well as some really nice dust and very little noise.

Thanks!

Quote from: RobertM
That's really lovely Mark and I think that combination works really well.  I especially like the way NGC2023 looks like a three dimensional tunnel with excellent detail.

Thanks Robert - I always value your opinion.

Quote from: JohnP
Mark - that full size image is immense - very smooth result & superb detail - would look superb printed A3 or A2... John

Cheers, John!

Title: Re: Horsehead 28/30 Jan
Post by: MarkS on Feb 10, 2019, 13:14:55
Quote from: Apophis
Stunning image , Mark.
What was your processing train?
Roger

Thanks Roger.

The main processing steps were as follows:
1) 200% scale Bayer Drizzle stacking in PixInsight
2) Re-register R&B channels to G channel to deal with atmospheric dispersion
3) Dynamic Background Extraction and BackgroundNeutralisation in PixInsight
4) White balance using PhotometricColorCalibration in PixInsight
5) Apply Sony A7S sRGB colour correction matrix (from DXOLab) in PixInsight
6) Apply gamma 2.2 in PixInsight
7) ArcsinhStretch in PixInsight
8 ) Save as 16bit TIFF with embedded sRGB ICC colour profile
9) Apply Camera Raw Filter noise reduction in Photoshop CC
10) Apply slight blur and reduce image scale to 100%
11) More Camera Raw Filter noise reduction in Photoshop CC
12) Back to PixInsight to split luminance and chroma
13) Apply enhancements to the luminance to highlight structures (a DIY variety of unsharp masking)
14) Recombine luminance and chroma
15) Back to Photoshop for minor curves adjustments and further noise reduction

Mark




Title: Re: Horsehead 28/30 Jan
Post by: Apophis on Feb 10, 2019, 18:02:20
OK  :o , thanks Mark,
Roger
Title: Re: Horsehead 28/30 Jan
Post by: julian on Feb 11, 2019, 15:25:03
Mark you make it sound so easy.
Great image as always.

Julian
Title: Re: Horsehead 28/30 Jan
Post by: The Thing on Feb 11, 2019, 16:12:12
Seems like all the time you've spent on that C11 has paid off, what a lovely image. I'm taking note of the colours!
Title: Re: Horsehead 28/30 Jan
Post by: MarkS on Feb 11, 2019, 22:27:03
Quote from: Apophis
OK  :o , thanks Mark,
Roger

Well, you did ask  ;)

Mark
Title: Re: Horsehead 28/30 Jan
Post by: Hugh on Feb 12, 2019, 11:03:37
Wow!  That just about says it all.

Hugh
Title: Re: Horsehead 28/30 Jan
Post by: JohnP on Feb 12, 2019, 11:08:01
Out of interest Mark can we see an unprocessed 30 sec raw? John
Title: Re: Horsehead 28/30 Jan
Post by: Apophis on Feb 12, 2019, 11:53:19
If i had PI i would have been able to relate a bit more but still interesting the amount of steps.
Roger
Title: Re: Horsehead 28/30 Jan
Post by: MarkS on Feb 12, 2019, 20:05:50
Quote from: JohnP
Out of interest Mark can we see an unprocessed 30 sec raw? John

Sure, here's an out-of-camera JPEG, reduced in size:

(http://www.markshelley.co.uk/Astronomy/2019/Horsehead_DSC00501_small.jpg)

I used 420 of those!

Mark
Title: Re: Horsehead 28/30 Jan
Post by: JohnP on Feb 12, 2019, 20:10:33
Thks Mark - Surprising clean image for a single 30 sec sub. Have to say it is amazing when you put that single sub & the final image side-by-side. Once again you need to make sure you get an A2 print of this done - John
Title: Re: Horsehead 28/30 Jan
Post by: The Thing on Feb 12, 2019, 20:29:26
A few of years ago I'd have been happy to have that sub as a finished image!
Title: Re: Horsehead 28/30 Jan
Post by: RobertM on Feb 12, 2019, 20:42:54
Pretty impressive skies, I’d say it would take me at least 10-20 subs to get to the same  quality as that single frame.

Robert
Title: Re: Horsehead 28/30 Jan
Post by: Carole on Feb 12, 2019, 20:51:48
Yes, agree with all the above comments. 

Carole
Title: Re: Horsehead 28/30 Jan
Post by: Fay on Feb 14, 2019, 08:25:55
Great image Mark, as ever
Title: Re: Horsehead 28/30 Jan
Post by: MarkS on Feb 14, 2019, 08:50:21
I forgot to mention one very important benefit of using short exposures on the C11.  It completely removes the issue of star trailing caused by slight shifts in the primary mirror as the scope tracks across the sky. 

The usual way of avoiding this problem is to use an OAG (off-axis guider) but using short exposures is an excellent alternative.

Of course you need a camera with very low read noise - the Sony A7S at high ISO is perfect for this :)

Mark
Title: Re: Horsehead 28/30 Jan
Post by: Carole on Feb 14, 2019, 15:56:59
That is indeed a bonus.

Carole