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

Messier 81 M81 NGC 3031, (Bode's G.) Ursa Major, LRGB, 24'' CDK

Astrophotography Cassegrain CCD CMOS DSO Imaging Reflector
  • Please log in to reply
13 replies to this topic

#1 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 08 April 2021 - 12:18 PM

Messier 81  M81  NGC 3031, (Bode's G.) Ursa Major, LRGB, 24'' CDK

This large, bright galaxy was discovered by Bode on New Year's Eve 1774, then documented in 1779 by Mechain and Messier, who included it in his catalog as M81. The galaxy shows a prominent spiral structure, and is extensively studied at infrared wavelengths because of an active central supermassive black hole of 70 million solar masses, and because of rich star-forming regions in the spiral arms. The red regions in the spiral arms are stellar nurseries: large clouds of hydrogen gas incited to fluoresce by the ultraviolet energy absorbed from nearby stars. The blue floccules are OB Associations, immense clusters of large new stars of the very hot O and B spectral class, which have a spectacular but brief existence of only several million years. When such stars end their lives as supernovae, they enrich their galaxy with heavier elements and molecules essential for the formation of the next generation of stars, rocky planets, and of life itself.

M81 is 27 x 14 arcmin in apparent size, approximately 7 in apparent magnitude, and lies at a distance of about  12 million LY. It is estimated to be 90,000 LY in diameter, and to contain 250 billion stars. The galaxy is somewhat smaller, but similar in structure to the Milky Way.

The attached image was taken with a remote controlled (iTelescopes.net) Planewave CDK telescope, 610 x 4000 mm. It is a stack of 5 x 300 sec exposures for each LRGB filter, reprocessed with DSS, XnView, StarNet++, and StarTools.

Thank you for looking.

 

Z1LG.jpg


  • EXT64, elmiko, DuncanM and 12 others like this

#2 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 08 April 2021 - 12:19 PM

Z2LG.jpg


  • chrysalis, Hobby Astronomer, pyrasanth and 1 other like this

#3 pyrasanth

pyrasanth

    Soyuz

  • *****
  • Posts: 3,913
  • Joined: 08 Jan 2016

Posted 08 April 2021 - 12:21 PM

Are you receptive to comments around your image?- you did not mention if you were receptive to critique. Let me know I'd like to give my opinions.



#4 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 08 April 2021 - 12:43 PM

pyrasanth,

C&C always welcome, even when it hurts. But, be gentle. I am the sensitive kind.



#5 pyrasanth

pyrasanth

    Soyuz

  • *****
  • Posts: 3,913
  • Joined: 08 Jan 2016

Posted 08 April 2021 - 02:29 PM

Hi- Unless you are a master of the written word, words can be hurtful so I will start with a smile.gif. I never offer C&C in an offensive way.

 

You've had the opportunity to aquire data with a dream telescope and I presume under dark skies. I try & back up C&C with my own efforts as that has more value. Here is an earlier image that I took last year with the C14 which you may have seen https://www.astrobin...380v2s/?nc=user like your example this image does not have a lot of integration time and its under heavy light pollution.

 

I believe that the data you have captured can be processed much better with a little work. I think you should look closely at techniques of deconvolution, colour calibration and background neutalisation. There is a lot more detail that can be bought out in the core region- it is burnt out and deconvolution or HDRM may bring out a stack of detail that is potentilly lost.

 

The background is quite heavily clipped which means you have lost fringe details and the lovely Holmberg galaxy is missing from the image which when revealed is a great marker that your back ground has not been too far clipped-it's a shame because I would have liked to have seen this in your image especially as its from a 24" and not the 14" mirror that I have.

 

In summary- you have great data which has been not been lifted to its true potential by weaknesses in processing Kung -Fu, however, since the data is now yours you have all the time in the Universe to enhance the final and hopefully more appealing result.

 

In closing it is in no way a bad image  however the potential to be great is there and frankly my image is not great either but it does have a lot of detail especially around the core which your image really needs to lift above average.

 

Good luck & I hope I've been kind- clear skies to you all.


Edited by pyrasanth, 08 April 2021 - 03:54 PM.

  • dswtan, pfile and rekokich like this

#6 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 09 April 2021 - 09:51 AM

pyrasanth,

 

Thank you for your detailed and sensitive comments.

 

There is not much more in the background than noise and haze around bright sources of light. Download the attached luminance stack, and stretch it. I did listen to your advice, and recovered a few very faint galaxies which had escaped my attention. Also, I reduced color saturation, and did a bit more deconvolution, HDR, and entropy on M81, but may have overdone it. I am afraid this is the best I am able to do with the available data and my current skills. The CFO refuses to approve funds for longer integration time on this target. She requests an LRGBHa of M82 instead.

 

As for Holmberg IX, it lies just outside the top border of the frame. It did not show very well on the original, and it was not worth reframing the image to include it.

 

Z1LGS.jpg


Edited by rekokich, 09 April 2021 - 10:19 AM.


#7 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 09 April 2021 - 09:52 AM

Original L stack:

 

L stack.jpg



#8 matt_baker

matt_baker

    Explorer 1

  • -----
  • Posts: 56
  • Joined: 07 Feb 2018

Posted 09 April 2021 - 10:26 AM

Are you willing to share the data to play around with so I can see what I can get from it and maybe give you some pointers?

I do agree with pyrasanth. I feel the stars can look much better by utilizing arcsin stretch or masked stretch when used alongside starnet masks. Clipping does also seem to be an issue too. Other than that, I think it's a great picture

 

Matt



#9 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 10 April 2021 - 12:53 AM

pyrasanth and Matt,

 

You are welcome to the original LRGB stacks:

https://drive.google...JF4?usp=sharing

 

I would be interested to see your results. Meanwhile, I am making another go at this image with more conservative processing.

 

Rudy



#10 pyrasanth

pyrasanth

    Soyuz

  • *****
  • Posts: 3,913
  • Joined: 08 Jan 2016

Posted 10 April 2021 - 04:36 AM

pyrasanth and Matt,

 

You are welcome to the original LRGB stacks:

https://drive.google...JF4?usp=sharing

 

I would be interested to see your results. Meanwhile, I am making another go at this image with more conservative processing.

 

Rudy

Hi Rudy,

 

The stacks are in a jpeg format. This is a lossy format so to process these vital information has already been lost. 

 

To have a go at processing we would need the raw data- so original captured subs as they came from the telescope, flats, darks and bias masters would also be required. Only then will we have a chance of seeking the true potential of the data.

 

There is no pressure from my side to get these files from you however I won't be processing the data in the form it has been presented as it can't show anthing better than what you have currently presented. Most image processing tools can't work at their best with lossy data stacks- PixInsight won't allow the combination of jpeg stacks as an example of this.


Edited by pyrasanth, 10 April 2021 - 04:45 AM.


#11 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 10 April 2021 - 08:31 PM

pyrasanth,

 

I am sorry. The image was taken over a year ago. 5kx5k pix JPG 100 stacks are the only images I have saved. Due to enormous size, the original subs were discarded after initial processing.



#12 matt_baker

matt_baker

    Explorer 1

  • -----
  • Posts: 56
  • Joined: 07 Feb 2018

Posted 11 April 2021 - 10:44 AM

Did you keep the raw stacks? (not JPEG). Doesn't matter about every single sub, just the stack



#13 rekokich

rekokich

    Apollo

  • *****
  • topic starter
  • Posts: 1,075
  • Joined: 14 Sep 2014
  • Loc: Virginia

Posted 11 April 2021 - 11:45 AM

Matt,

 

I archived only field-corrected stacks in hi res JPG 100 format, as shared.



#14 Jared

Jared

    Fly Me to the Moon

  • *****
  • Posts: 6,628
  • Joined: 11 Oct 2005
  • Loc: Piedmont, California, U.S.

Posted 11 April 2021 - 08:17 PM

Matt,

 

I archived only field-corrected stacks in hi res JPG 100 format, as shared.

The catch with JPG 100 isn't the resolution--it's the bit depth. They are only eight bit files. So even though you have the full resolution (compressed), you can't do a lot of image manipulation without losing quality. Nothing wrong with dumping the individual frames, but if you want to be able to come back and re-process at a later date, you will want to save the stacks as (at a minimum) a 16 bit TIFF.


  • rekokich likes this


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





Also tagged with one or more of these keywords: Astrophotography, Cassegrain, CCD, CMOS, DSO, Imaging, Reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics