Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Why is My Ring Nebula Blown Out? Where's the Hole?

  • Please log in to reply
28 replies to this topic

#1 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 11:25 AM

Hi Guys,

 

The image below is of the Ring Nebula.  I was surprised to see that after stacking the hole in the middle of the Ring was blown out (over saturated?). 

 

I took rather short exposures of 120s with a IDAS NBZ filter (during a full moon but in the opposite side of the sky).  I used an ASI533MC-P with my Orion 8" Newt.  Should I have taken shorter exposures - maybe 60s? 

 

I only stacked 83 subs because something happened in the middle of the night and my tracking failed for the other 67 subs - so I had to throw them out (the stars were oval and some subs showed trails).  The 83 subs I used were in good shape with decently round stars. 

 

The first pic is the stacked image and the second pic is an individual sub in which you can still see the hole.  Any idea what I did wrong?

 

Ring_Nebula_II-St-2mp.jpg

 

Capture.JPG



#2 KungFood

KungFood

    Mariner 2

  • -----
  • Posts: 250
  • Joined: 18 Jul 2014
  • Loc: Dallas, Tx

Posted 22 September 2021 - 11:28 AM

Which stacking method was used, median, average, etc, and in what software?



#3 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 11:37 AM

Which stacking method was used, median, average, etc, and in what software?

I use Astro Pixel Processor (APP) so it's all automated.



#4 KungFood

KungFood

    Mariner 2

  • -----
  • Posts: 250
  • Joined: 18 Jul 2014
  • Loc: Dallas, Tx

Posted 22 September 2021 - 11:42 AM

I don't have experience with APP, but for the sake of troubleshooting by elimination, you might try stacking in DSS, its free and fairly easy to use with default settings. If the problem persists even then, you can eliminate (most likely) it being a software setting. If it stacks correctly in DSS, then you can go back into APP and try to suss out the seeting at fault. Sorry I can't be more help.

 

*edit* just from looking at it, I would guess that it is using additive stacking without dividing the result.


Edited by KungFood, 22 September 2021 - 11:43 AM.

  • limeyx likes this

#5 bunyon

bunyon

    Fly Me to the Moon

  • *****
  • Posts: 5,212
  • Joined: 23 Oct 2010
  • Loc: Winston-Salem, NC

Posted 22 September 2021 - 11:52 AM

Does it do automated processing? It looks like what you'd get after a simple stretch (as opposed to more judicious use of curves) of the histogram.



#6 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 11:55 AM

Good idea, I'll try DSS and see what results I get.  I can also play with the settings in APP and see if that makes a difference (I usually just stick with the default settings).



#7 idclimber

idclimber

    Surveyor 1

  • *****
  • Posts: 1,854
  • Joined: 08 Apr 2016
  • Loc: McCall Idaho

Posted 22 September 2021 - 11:58 AM

Your problem is not stacking. It is in how the data is stretched after it is integrated. I can't help you with APP or DSS but PI does have a number of tools and strategies for this that will work better than what you are doing now. 


  • imtl, wrnchhead and OldManSky like this

#8 astroian

astroian

    Ranger 4

  • -----
  • Posts: 393
  • Joined: 21 Sep 2016
  • Loc: Swindon, UK

Posted 22 September 2021 - 12:01 PM

Unless I’m missing simething, you’ve stretch the image to bring out the outer halo. This is very dim. The central hole is not empty and contains gas that is dim compared to the surrounding ring, but is brighter than the halo. So stretching to reveal the outer halo will make everything else very bright/ saturated.

Well done on getting that outer halo. If you capture even more signal there is another, even dimmer ring of material beyond that one!

Cheers,
Ian

#9 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:06 PM

Your problem is not stacking. It is in how the data is stretched after it is integrated. I can't help you with APP or DSS but PI does have a number of tools and strategies for this that will work better than what you are doing now. 

I think you're right.  I lowered the stretch and can now see the hole but it's still rather blown out.  This is the minimum stretch.  I'm going to save it unstretched and then stretch it in StarTools - maybe that will help.

 

 

Ring_Nebula_II-St_2-2MP.jpg



#10 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:12 PM

I'm thinking it's time I bite the bullet and purchase PI



#11 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:14 PM

Is there a way to stretch the Ring Nebula separately from the rest of the image?  It seems the Nebula needs very little stretching but the rest of the image needs more.  Is this possible?



#12 DubbelDerp

DubbelDerp

    Surveyor 1

  • *****
  • Posts: 1,860
  • Joined: 14 Sep 2018
  • Loc: Upper Peninsula of Michigan

Posted 22 September 2021 - 12:16 PM

Do you have an unstretched stack that you can upload and share? It's usually a lot easier to diagnose when looking at the raw stack.



#13 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:20 PM

Yes - here it is . . .

 

Ring_Nebula_II-NoSt-2MP.jpg

 



#14 DubbelDerp

DubbelDerp

    Surveyor 1

  • *****
  • Posts: 1,860
  • Joined: 14 Sep 2018
  • Loc: Upper Peninsula of Michigan

Posted 22 September 2021 - 12:24 PM

Sorry, I meant the FITS or TIFF itself... but the JPG of it looks pretty reasonable, if perhaps a bit bright in the nebula.



#15 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:27 PM

I have to say I think my new IDAS NBZ filter rocks!  Finally no halos!



#16 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 12:28 PM

I have to run everyone - promised my wife I'd bring her to the Van Gogh Exhibit here in Scottsdale - but I'll be checking my phone for further feedback.  Thanks!



#17 Alex McConahay

Alex McConahay

    Voyager 1

  • *****
  • Posts: 10,651
  • Joined: 11 Aug 2008
  • Loc: Moreno Valley, CA

Posted 22 September 2021 - 02:04 PM

Try masking out everything but the nebula and stretching that area differently from the rest of the image. 

 

Alex


  • rekokich and belliott4488 like this

#18 rekokich

rekokich

    Apollo

  • *****
  • Posts: 1,173
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 22 September 2021 - 02:06 PM

Nebula and starfield processed separately, then layered in StarTools.

 

z1140.jpg


  • Mike in Rancho likes this

#19 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 02:39 PM

Nebula and starfield processed separately, then layered in StarTools.

 

attachicon.gifz1140.jpg

Wow.  That’s the trick. Thank you much Rekokich. I'm going to try and replicate it doing what Alex said. 

 

Thanks guys!



#20 TelescopeGreg

TelescopeGreg

    Soyuz

  • -----
  • Posts: 3,558
  • Joined: 16 Jul 2018
  • Loc: Auburn, California, USA

Posted 22 September 2021 - 03:22 PM

You should be able to do it all in one pass with StarTools.  Use AutoDev with a Region of Interest (mouse a box) around just the Nebula, followed by Wipe, a re-do of AutoDev, then Color.

 

The Ring Nebula is dim, but not that dim, and doesn't usually require a lot of specialized processing.



#21 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 03:31 PM

You should be able to do it all in one pass with StarTools.  Use AutoDev with a Region of Interest (mouse a box) around just the Nebula, followed by Wipe, a re-do of AutoDev, then Color.

 

The Ring Nebula is dim, but not that dim, and doesn't usually require a lot of specialized processing.

Sounds good. Ill give it a try as soon as I get home.

 

I’m so disappointed I had to throw away so many subs. I have to assume the more integration one has, the more cropping that can be done. I was hoping to crop enough to enlarge the nebula. 



#22 TelescopeGreg

TelescopeGreg

    Soyuz

  • -----
  • Posts: 3,558
  • Joined: 16 Jul 2018
  • Loc: Auburn, California, USA

Posted 22 September 2021 - 03:52 PM

Sounds good. Ill give it a try as soon as I get home.

 

I’m so disappointed I had to throw away so many subs. I have to assume the more integration one has, the more cropping that can be done. I was hoping to crop enough to enlarge the nebula. 

If the subs are all good, including them all should improve things.  You can't have too many good subs, as long as your computer (and patience) can handle them.

 

I never "groked" APP, but DSS goes a good job with stacking, and it's my "go to" for the more challenging stacks.  Another free tool is ASTAP; easier to use and also multi-platform.  That said, the advice from me is to stick with one tool and get to know it well.  They're all very capable and flexible, and can produce exceptional results.  However any tool used with the wrong settings is pretty much guaranteed to disappoint.  This hobby, perhaps more than most, doesn't work well with short attention spans.



#23 Mike in Rancho

Mike in Rancho

    Apollo

  • -----
  • Posts: 1,488
  • Joined: 15 Oct 2020
  • Loc: Alta Loma, CA

Posted 22 September 2021 - 04:03 PM

I just did the Ring a few days back.  https://www.cloudyni...cause-i-had-to/

 

Surprisingly bright and tricky.  I only had 2 hours on target, but stretching (full no-ROI AutoDev) really turns it into a very bright, very white, donut.  lol.gif

 

In the end I used a ROI that just captured a slice of the Ring, in order to tame it down.  I lost whatever of the outer ring my limited integration captured, but that was necessary for the overall image.

 

I then used strong HDR module settings (twice, reveal all and reveal core), along with expanded dynamic range in SVDecon, in order to obtain M57 detail.  As above, things looked better with the stars and M57 stretched separately and layered back together.  Fairly easy to do with this target.

 

And because it's so small, I also went back and restacked in DSS using a custom rectangle (i.e. crop) and 2x drizzle, which also helped.  I'll go back and try some additional things on it later, but I have to get a few computer issues settle first.



#24 TelescopeGreg

TelescopeGreg

    Soyuz

  • -----
  • Posts: 3,558
  • Joined: 16 Jul 2018
  • Loc: Auburn, California, USA

Posted 22 September 2021 - 05:37 PM

Nice, Mike. 

 

Perhaps part of the difficulty comes from the (presumed) bright skies where the OP is, not to mention the Moon being up there.  If so, the "fix" is to wait a few weeks for the Moon to get out of the way, and take a bunch of images.  More time on the target is the primary solution to light pollution. 

 

By way of comparison, earlier this month I grabbed an image of the Ring at a Star Party.  Skies there were Bortle 4, and no Moon.  A little bit of smoke, but not too bad.  Single 2 minute sub at 300 gain with my 130mm f/7 scope and the ASI2600MC camera.  That was about as long as I wanted to have the assembled half-dozen on-lookers wait, so I cranked up the gain (normally I use 100).  Still, I got a lot of color in the nebula.

 

Here's the full image.  No processing, except that the camera was binned 2x2.  The software is configured to save both a jpg and fits; this is the 3k x 2k pixel jpg version (not sure what the CN site will do to it...).

M57_NGC6720_120s_300_2x2_20210905_033942.jpg

 

And a simple crop of the center:

 

M57 Ring Nebula - Single 2 min exposure 4-Sep 2021 Nevada City (cropped).jpg


  • Mike in Rancho likes this

#25 Tom62e

Tom62e

    Viking 1

  • *****
  • topic starter
  • Posts: 547
  • Joined: 25 May 2014
  • Loc: Scottsdale, AZ

Posted 22 September 2021 - 05:55 PM

This hobby, perhaps more than most, doesn't work well with short attention spans.

 

Very Well Said!




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics