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

2+ hours on M33 Triangulum galaxy with unmodded dslr

  • Please log in to reply
13 replies to this topic

#1 pptw

pptw

    Sputnik

  • -----
  • topic starter
  • Posts: 43
  • Joined: 08 Feb 2020
  • Loc: Denmark, Europe

Posted 20 January 2021 - 03:06 PM

Hi all,

 

Finally weather was good and I had the opportunity to go out again, and shoot the triangulum galaxy.

 

At the moment, the traingulum galaxy is nice and high in the sky, and little light pollution towards my south west. Picture was shot around new moon.

 

I only realised weather was turning good a bit too late so i think my triplet was not fully cooled down, and therefore some bloating on the bottom side of brighter stars... Any idea otherwise? Telescope was outside for max20min when I started shooting, coming from warm office space.

 

Shot from dark bortle 4, Nikon D5300 on ISO200 and no flats/darks/bias. SW Eq5 with stepper motor and esprit 80. 280 shots of 30s, adding up to 2h20m expsosure. No filters.

 

Some of the basic operations in Siril: background exraction, photometric color calibration, removing green noise, histogram transformation, median filter and deconvolution.

In photoshop some masked processing: star reduction, levels, curves, vibrance and saturation

 

https://www.astrobin.com/9a590m/

 

Feedback on processing and final result is very welcome! I tend to struggle a bit what the 'right' order of processing is in Siril. I guess some processing steps are quite order invariant, while other are not. Any help there?

 

 

Attached Thumbnails

  • result_ps_small copy.jpg

  • Jim Waters, mikewayne3, AngelC and 12 others like this

#2 giganova

giganova

    Vostok 1

  • *****
  • Posts: 122
  • Joined: 14 Oct 2020
  • Loc: Washington, DC

Posted 20 January 2021 - 03:25 PM

Why do you only shoot at ISO 200? You can crank it up to ISO 1600 and won't see a difference, but the exposure time will be 6x smaller, 25 min instead of 2h20min.



#3 Jim Waters

Jim Waters

    Fly Me to the Moon

  • *****
  • Posts: 5,353
  • Joined: 21 Oct 2007
  • Loc: Phoenix, AZ USA

Posted 20 January 2021 - 03:37 PM

Nice image and processing.  FYI - see the link below.

http://dslr-astropho...-nikon-cameras/


  • RogerM likes this

#4 fewayne

fewayne

    Apollo

  • *****
  • Posts: 1,195
  • Joined: 10 Sep 2017
  • Loc: Madison, WI, USA

Posted 20 January 2021 - 04:20 PM

I'm with Jim, that's quite nice. I might make the artistic choice of a somewhat brighter image overall, both the midtones and the background. The latter seems clipped to black or near-black to me.


  • chili555 likes this

#5 ntph

ntph

    Vostok 1

  • -----
  • Posts: 152
  • Joined: 20 Oct 2012
  • Loc: Sudbury, ON

Posted 20 January 2021 - 04:41 PM

Like the others say, nice image! 

 

If you are really under Bortle 4 skies, you might consider using longer exposures, if your mount allows, as well as increasing your ISO. Experimentation is the key to progress in this endeavour!

 

As far as workflow suggestions, I am not familiar with Siril, but I suspect the basic steps would be the same across programs. As such, many if not all sources suggest deconvolution be done early and on linear images, after gradient management and before noise reduction. As for green noise reduction (SCNR in PixInsight-speak), some advocate it early, some at the end and others use it on either end depending on data. 

 

You probably have seen a generic workflow, but here is one from Harry's Astroshed Processing tutorials, based on PixInsight. 

PI Workflow.png

 

Good luck and clear skies

 

 

 


  • Jim Waters likes this

#6 pptw

pptw

    Sputnik

  • -----
  • topic starter
  • Posts: 43
  • Joined: 08 Feb 2020
  • Loc: Denmark, Europe

Posted 21 January 2021 - 02:53 AM

Hi all, thanks for the positive comments.

The reason for me shooting iso200 is because the link Jim posted(that was my reference before starting the shoot) clearly states the Nikon D5300 can be considered iso-less, so any iso higher than 200, will generate more noise while the high iso result can be achieved on iso200 with less noise and post processing. Is this correct? Or did I misunderstand?

My EQ5 mount does not allow me to shoot 1min exposures in general, too much streaks on the stars. I can however shoot more 30s shots, it’s just a lot of storage and processing time.

I’m happy you guys like the image! Regarding the black background, indeed maybe I pushed it too far. Regarding overall brightness, yes it’s a bit dim to let everything be smooth and not too stretched but let me give it a try later to pull things out a bit more :-)

@ntph thanks for the overview! I will spend some time to align with Siril and see if I can match. Your help is much appreciated!
  • Jim Waters likes this

#7 Huangdi

Huangdi

    Apollo

  • *****
  • Posts: 1,005
  • Joined: 24 Jul 2019

Posted 21 January 2021 - 03:41 AM

Why do you only shoot at ISO 200? You can crank it up to ISO 1600 and won't see a difference, but the exposure time will be 6x smaller, 25 min instead of 2h20min.


Uhh... No.

You definitely will see a difference - reduced dynamic range.

And you definitely misunderstood something there. Increasing the ISO does NOT change the signal you gathered. 2 hours integration are 2 hours integration.
  • Jim Waters, Boeglewatcher, RogerM and 2 others like this

#8 jonnybravo0311

jonnybravo0311

    Apollo

  • *****
  • Posts: 1,084
  • Joined: 05 Nov 2020
  • Loc: NJ, US

Posted 21 January 2021 - 02:35 PM

I'm always amazed seeing similar images taken under different quality skies. For example, I just recently imaged M33 using my G9, GT81 and 0.8x reducer. I have a very similar integration time as well (151 minutes vs your 140). The primary difference in the data is that OP's data was gathered under Bortle 4 skies, while mine was captured under Bortle 6 (maybe closer to 7, but I don't have an SQM meter to validate that). Here's my result:
 
get.jpg?insecure 
 
Click the above picture for details. Take a close look at mine, and you'll clearly see a whole lot more noise than what is present in OP's image. If we pretend for a second that all other things were equal, then if OP lives under the darkest B4 skies, and I am under the brightest B6, I would need to capture about 12 times the data to get the same quality as what OP captured. In other words, I'd need 28 hours to match what OP gathered in 2.3 hours.


  • sbharrat likes this

#9 pptw

pptw

    Sputnik

  • -----
  • topic starter
  • Posts: 43
  • Joined: 08 Feb 2020
  • Loc: Denmark, Europe

Posted 21 January 2021 - 03:36 PM

He Johnny thanks for your post really cool to see what kind of image you acquire with pretty similar hardware but different bortle skies! Maybe my background seems less noisy because I didn't pull out the details as much and my overal image is less bright, but the difference in borrtle is pretty evident.

 

Here attached just a simple overlay of screenshots of bost astronbin versions.

 

Seeing your image makes me appreciate dark skies even more! 28h sounds insane, given the 2 hours i might capture every 1-2 months haha.

 

 

 

Btw I did some SQM measurements with a phone app (dark sky meter iOS) that night, giving 21.4-21.6 SQM...

Attached Thumbnails

  • comparison_johnny_bortle6_s.jpg

Edited by pptw, 21 January 2021 - 03:37 PM.

  • Jim Waters, jonnybravo0311 and sbharrat like this

#10 jonnybravo0311

jonnybravo0311

    Apollo

  • *****
  • Posts: 1,084
  • Joined: 05 Nov 2020
  • Loc: NJ, US

Posted 21 January 2021 - 03:41 PM

If I could give this more than one like, I would. The composite you created showing both of our images together is fantastic!


  • pptw likes this

#11 Seaquel47

Seaquel47

    Vostok 1

  • *****
  • Posts: 182
  • Joined: 19 May 2019
  • Loc: Punta Gorda, Florida

Posted 21 January 2021 - 03:48 PM

I love the comparison, good work by both of you.  That really provides some food for thought.


  • pptw likes this

#12 pptw

pptw

    Sputnik

  • -----
  • topic starter
  • Posts: 43
  • Joined: 08 Feb 2020
  • Loc: Denmark, Europe

Posted 21 January 2021 - 04:02 PM

If I could give this more than one like, I would. The composite you created showing both of our images together is fantastic!

Thank you sir! Would love to make more of these comparisons, especially because it is (apart from difference in equipment and post processing) - as seaquel mentions - very good food for thought and a nice reference to people who wonder about the difference. And fun too.

 

Furthermore to feed the discussion up a bit; what about the earlier posts on ISO200 vs ISO1600? yes, 1600 would be more amplification of the incoming photons, giving more brightness to my image, but also (exponentially?) more noise? How would the ratios develop? The url above mentions the 200 is best for my camera. Any thoughts, facts, ideas or proofs?



#13 jonnybravo0311

jonnybravo0311

    Apollo

  • *****
  • Posts: 1,084
  • Joined: 05 Nov 2020
  • Loc: NJ, US

Posted 21 January 2021 - 04:59 PM

Your D5300 works far better at lower ISO than my G9. Supposedly 1600 is about where I should be... I could feasibly be at 1000, since that's about where things start to level off, but I go with 1600 because it is a "real" stop. Here's a chart comparing the D5300 to my G9:

 

G9 V d5300

 

Your D5300 is the nice smooth, level blue line. My G9 is the not so smooth and level black line.

 

Since there's not a whole lot of difference in the read noise of your D5300's sensor, you might as well shoot at the lowest ISO to get the best dynamic range.



#14 pptw

pptw

    Sputnik

  • -----
  • topic starter
  • Posts: 43
  • Joined: 08 Feb 2020
  • Loc: Denmark, Europe

Posted 22 January 2021 - 02:09 PM

Thanks Johnny, then I understood the theory right. I will keep shooting in low iso.

Fantastic to see how a linear nearly-pitch-dark picture from iso200 with only some dim stars can show a wonderful picture after boosting the levels!


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