Author Topic: IC 5146 Cocoon Nebula **REPROCESSED  (Read 746 times)

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Apophis

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IC 5146 Cocoon Nebula **REPROCESSED
« on: Aug 02, 2018, 16:34:56 »

My first colour LRGB
NEW VERSION
vvvvvvvvvvvvv

I had LRGB data before and after meridian flip , processed the two sets separately in PS and used DSS to stack the images after rotating one of them in PS.
Reprocessed in PS CC and DSS and also using Luminance as a reference frame LRGB all aligned in DSS.
I love the stars in this one!

Updated capture details
---------------------------
43 x  Luminance @ 80s
35 x R,30 x G,32 x B, @ 80s
Minus 25oC

Imaging telescope:SkyWatcher 120ED Imaging System for Canon DSLR Cameras
Imaging camera:ZWO ASI183MM Monochrome 4/3" CMOS USB3.0 Deep Sky Imager Camera
Mount:Skywatcher EQ6-R PRO Synscan
Guiding cameras:Skywatcher 9x50 Finderscope,  QHYCCD 5L-II MONO
Focal reducer:Skywatcher 0.85x Focal Reducer/Corrector for Evostar-120ED
Software:ADOBE PHOTOSHOP CC,  DeepSkyStacker x64 by Luc Coiffier, Tony Cook, David C. Partridge Deepsky Stacker 4.1 64bit,  Astro Photography Tool
Filters:ZWO CCD LRGB Filter-Set 36mm,  zwo EFW 7-position Filter Wheel for 36mm Unmounted Filters
Accessory:QHYCCD PoleMaster
Resolution: 5496x3665
Dates: Aug. 2, 2018
Frames: 40x80"
Integration: 0.9 hours
Avg. Moon age: 19.93 days
Avg. Moon phase: 72.71%
Astrometry.net job: 2177140
RA center: 328.341 degrees
DEC center: 47.264 degrees
Pixel scale: 0.630 arcsec/pixel
Orientation: 75.153 degrees
Field radius: 0.578 degrees
Locations: Home, Worthing, West Sussex, United Kingdom
Data source: Backyard
Roger
« Last Edit: Aug 14, 2018, 20:48:27 by Apophis »

The Thing

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Re: IC 5146 Cocoon Nebula
« Reply #1 on: Aug 02, 2018, 16:46:02 »
The stars are a bit iffy. I think it may be that under the different filters the star sizes are different?

Other than that a good start. The processing has taken me forever to get a handle on and I've got tons to learn. Good luck!

Duncan
¯\_(ツ)_/¯ (Gallic shrug :))
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Apophis

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Re: IC 5146 Cocoon Nebula
« Reply #2 on: Aug 02, 2018, 16:57:06 »
Thanks duncan , pleased considering the centre of worthing.
So not a dark sky site.
Roger

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Re: IC 5146 Cocoon Nebula
« Reply #3 on: Aug 02, 2018, 17:14:25 »
I know what a pain light pollution is. What I would do is use Sharpcap 3 (worth a tenner) to characterize your camera taking into account the sky brightness, it will suggest a gain exposure and the number of subs to get the best out of the camera in the conditions. I suspect a lot of shorter subs will produce better results. I've been using 5min subs as with my DSLR and have run into problems, Sharpcap recommended very short subs a 1500 of them. I'm going to take the hint, however that many subs is a pain to process. DSS seems to have a 246 sub limit, just debayering 1000 subs took over 2h on a fast pc bought for the purpose! I think 8secs is a little short...

Btw I have light pollution until 11pm. Terrible😉

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Carole

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Re: IC 5146 Cocoon Nebula
« Reply #4 on: Aug 02, 2018, 20:41:15 »
For your first combination of Luminance, Red, Green and blue filters together you have done a very good job, it's not easy when you are starting out.

I already commented to you about the stars as you tend to burn them out.  Practice makes perfect though.
Quote
I think it may be that under the different filters the star sizes are different?

That is indeed the case and it can be tricky to manage.  But first of all Roger needs to try processing the stars more gently, I have been teaching him but I am not sure what he is doing when left to his own devices. 

Roger, maybe get the stretching of the stars right first and worry about getting the star colour after. 

But for a first "go" at LRGB he has done very well.

Carole

MarkS

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Re: IC 5146 Cocoon Nebula
« Reply #5 on: Aug 02, 2018, 21:00:37 »
You've got an image!  Your first LRGB image!  You're now have experience that I've never gained :)

The processing is not perfect but congratulations on your first attempt.

Mark

MarkS

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Re: IC 5146 Cocoon Nebula
« Reply #6 on: Aug 02, 2018, 21:05:59 »
Quote from: The Thing
I've been using 5min subs as with my DSLR and have run into problems, Sharpcap recommended very short subs a 1500 of them.

Very short subs with a DSLR? Seriously?  It doesn't sound right to me, not for deep sky imaging at least.  What length subs did it suggest?  What f-ratio did you give it?

Unfortunately I see a lot of faulty maths in various discussions on forums, also good maths based on faulty assumptions.

P.S. I get away with short subs with my Sony A7S because of the very low read noise - 1e RMS.  The read noise of most DSLR cameras goes nowhere near that low and so with very short subs it becomes the dominant (but avoidable) source of noise in the final image.

Mark

The Thing

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Re: IC 5146 Cocoon Nebula
« Reply #7 on: Aug 02, 2018, 22:46:59 »
No! With my ASI294MCPro! 1656 subs x 8.2s at unity gain was suggested, I did 1000 as a test. I did a quick stack of 249 of them in DSS and it didn't look bad.
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MarkS

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Re: IC 5146 Cocoon Nebula
« Reply #8 on: Aug 02, 2018, 23:32:29 »
Quote from: The Thing
No! With my ASI294MCPro! 1656 subs x 8.2s at unity gain was suggested, I did 1000 as a test. I did a quick stack of 249 of them in DSS and it didn't look bad.

Yes, you could just about get away with 8sec because you have such a low read noise.  30sec is more practical though in terms of number of subs.

Mark

Apophis

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Re: IC 5146 Cocoon Nebula
« Reply #9 on: Aug 03, 2018, 06:38:18 »
I know what a pain light pollution is. What I would do is use Sharpcap 3 (worth a tenner) to characterize your camera taking into account the sky brightness, it will suggest a gain exposure and the number of subs to get the best out of the camera in the conditions. I suspect a lot of shorter subs will produce better results. I've been using 5min subs as with my DSLR and have run into problems, Sharpcap recommended very short subs a 1500 of them. I'm going to take the hint, however that many subs is a pain to process. DSS seems to have a 246 sub limit, just debayering 1000 subs took over 2h on a fast pc bought for the purpose! I think 8secs is a little short...

Btw I have light pollution until 11pm. Terrible


Hi Duncan,
 Yes i found these tables on CloudyNights.

https://www.cloudynights.com/topic/616524-sub-exposure-tables-for-the-zwo-asi183mm-and-qhy183m-and-colour-versions/

Interested to know what everyone thinks.
Roger

MarkS

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Re: IC 5146 Cocoon Nebula
« Reply #10 on: Aug 03, 2018, 22:14:29 »
I know what a pain light pollution is. What I would do is use Sharpcap 3 (worth a tenner) to characterize your camera taking into account the sky brightness, it will suggest a gain exposure and the number of subs to get the best out of the camera in the conditions. I suspect a lot of shorter subs will produce better results. I've been using 5min subs as with my DSLR and have run into problems, Sharpcap recommended very short subs a 1500 of them. I'm going to take the hint, however that many subs is a pain to process. DSS seems to have a 246 sub limit, just debayering 1000 subs took over 2h on a fast pc bought for the purpose! I think 8secs is a little short...

Btw I have light pollution until 11pm. Terrible


Hi Duncan,
 Yes i found these tables on CloudyNights.

https://www.cloudynights.com/topic/616524-sub-exposure-tables-for-the-zwo-asi183mm-and-qhy183m-and-colour-versions/

Interested to know what everyone thinks.
Roger

I've followed Ray's (Shiraz's) work on Cloudy Nights and he is one of the (very) few people whose calculations I trust.  Treat those exposure lengths as as minimum - in other words feel free to use longer exposures but don't use shorter exposures.  By the way, do you know own your light pollution level on a magnitude scale?  Otherwise you'll find difficulty using those tables.

Mark

Apophis

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Re: IC 5146 Cocoon Nebula
« Reply #11 on: Aug 04, 2018, 01:35:21 »
ive got a sqm.
Roger