Hemisphere:  Northern  ·  Constellation: Vulpecula (Vul)  ·  Contains:  Dumbbell Nebula  ·  M 27  ·  NGC 6853  ·  PK060-03.1
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M27 Deep & HR (Newton 12" lucky imaging  & Newton 10" and RC16" long exposures), 



    
        

            Mathieu Guinot
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M27 Deep & HR (Newton 12" lucky imaging & Newton 10" and RC16" long exposures)

Getting plate-solving status, please wait...
M27 Deep & HR (Newton 12" lucky imaging  & Newton 10" and RC16" long exposures), 



    
        

            Mathieu Guinot
Powered byPixInsight

M27 Deep & HR (Newton 12" lucky imaging & Newton 10" and RC16" long exposures)

Acquisition details

Dates:
Nov. 14, 2021
Frames:
Integration:
0
Avg. Moon age:
10.29 days
Avg. Moon phase:
79.03%

RA center: 19h59m35s.948

DEC center: +22°4309.53

Pixel scale: 0.407 arcsec/pixel

Orientation: -49.518 degrees

Field radius: 0.328 degrees

WCS transformation: thin plate spline

More info:Open 

Resolution: 4096x4096

Data source: Backyard

Description

Halpha and Oiii long exposures with Newton 10" and ASI2600mm : 224 x 300s
Halpha and Oiii long exposures with RC16" and ASI2600mm : 200x300s
RVB long exposures with Newton 10" and ASI2600mm : 90x120s

Halpha lucky imaging with Newton 12"and Playerone Neptune color II :  5000x2.5s
IR - RVB lucky imaging with Newton 12"and Playerone Neptune color II : 40000x500ms


Some time after the finalization of my image of M27 in the summer of 2021, made with a Newton 250mm and ASI2600mm camera with 21h40 of long exposures, I came across the superb high resolution image made by Stephane Gonzales (Exaxe) in lucky imaging (short exposures).

I then decided to contact Stéphane to propose him to mix our two images and thus benefit from his high resolution on the heart of the nebula thanks to his short exposures in Halpha and IR, and from the signal/noise ratio obtained on the extensions of the nebula thanks to the long exposures on my HORVB image in order to create a composite image taking the best advantage of the two images.
Stephane is willing to take on the project and sends me his Halpha + IR luminance so that I can start trying to insert his image into mine.

Having already tried this type of experiment with other astrophotographers, Stéphane rightly anticipates that the result may lack coherence due to the difference in sampling and resolution between our images.
At the same time, and by pure coincidence, my friend Sébastien Kuenlin contacted me because: he would like to try to mix his image of M27 made a few months earlier with his new RC400mm f/8 telescope with mine in order to benefit from the details of his image and the signal on my extensions!
The junction then takes shape since Sebastien's image made at 0.5"/pixel with a FWHM around 1.8" is slightly more resolved than mine made at 0.8"/pixel with an average FWHM of about 2.5" and thus approaches Stephane's image made at 0.3"/pixel with a FWHM close to 1".
The project then takes shape in a new form using 3 images: Stephane's heart, close extensions of Sébastien's, and far extensions of my image. The coherence then becomes more convincing between the samplings with this progressivity from the centre at 0.3"/pixel to the close extensions at 0.5"/pixel and then the far extensions at 0.8"/pixel.

- Once the raw stacks are collected, the first phase of the work follows, which I carry out by inlaying the core + close extensions of Sébastien's M27 into my image. This step is carried out in linear (before histogram editing) in order to ensure a dynamic match so as not to alter the difference in luminosity of the object between the core and the extensions. This mixing is carried out on the Halpha and Oiii layers.
- Sébastien is in charge of the second phase which consists of processing the composite images obtained from Halpha and Oiii (deconvolution, noise processing, histogram enhancement, sharpening, etc.), mixing them to obtain a HOO colour image, and integrating the colour of the stars obtained by the RGB layer of my image. 
- Finally, we collaborate with Sébastien on the last phase, which consists in inlaying the non-linear image provided by Stéphane, on which the deconvolution, sharpening etc. treatments have already been performed by him with his technique from planetary astrophotography, which uses the same software and process to process deep sky images acquired in lucky imaging. 


The processing of the M27 nebula always presents a certain difficulty and forces choices because of the great difference in luminosity between the core and the extensions on the one hand, and the strong presence of Halpha and Oiii signals on identical zones on the other hand.
These artistic choices have been made with maximum respect for the scientific coherence of the object, although this is not 100% possible: indeed, one obtains a saturated core if one wants to take advantage of the signal on the most distant extensions, or one does not distinguish these if one wants to maintain an unsaturated core. It is therefore necessary to use HDR processing as sparingly as possible, which inevitably alters the object's dynamic range but allows a compromise to highlight the different signals making up the nebula.

In the end we are very happy to present the fruit of this work with the objectives fulfilled:

- to enjoy the details of the short exposures
- to take advantage of the extensions of the long exposures 
- to ensure coherence between the levels of detail thanks to the intermediate image taken in long exposure at long focal length
- keep the dynamics of the object as "real" as possible
- not to perceive any artefact or transition linked to the mixing of the three images


Sébastien, Stéphane and Mathieu, November 2021

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M27 Deep & HR (Newton 12" lucky imaging  & Newton 10" and RC16" long exposures), 



    
        

            Mathieu Guinot