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M81-M82 in HaLRGB (no IFN)


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This is my second galaxy shot of the season. I thought of redoing some targets that I tried before when I was only starting my AP journey and M81-M82 are a pair that were always on my mind.

Living in Bushey, UK, on the outskirts of London, under bortle 7 skies and with the telescopes in the shade of a parasol that's protecting them from the direct beam of a streetlight doesn't really allow me to go deep enough to capture any IFN but I really don't mind.

I'm perfectly happy that I can still get results like this. I have to integrate quite a lot though, 22 hours on this one.

I drizzeled the stack so I can crop the galaxies separetely and preserve the details.

Technical details:

Equipment used:
Eq6
AstroTech 106LE with upgraded Moonlite focuser
TSFlat 2" field flattener
ASI294MM Pro Cmos camera, cooled at - 15°C
8x1.25" ZWO USB filterwheel
Chroma 1.25" LRGB and 3nm 1.25" Ha filters
Qhyccd QHY5L-IIM guide camera
9x50mm finder-guider
Qhyccd Polemaster
 
Software used:
Eqmod, SGP - Sequence Generator Pro, PHD2, Stellarium with stellariumScope, SharpCap for polar alignment
 
Location: Bushey, bortle 7
 
Dates:Feb. 27, 2021 , April 4, 2021
 
Frames:
Chroma 1.25" Blue: 39x180" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Blue: 18x300" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Green: 41x180" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Green: 15x300" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Lum: 29x300" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Red: 41x180" (gain: 125.00) -15C bin 2x2
Chroma 1.25" Red: 15x300" (gain: 125.00) -15C bin 2x2
Chroma 3nm Ha 1.25": 9x300" (gain: 200.00) -15C bin 2x2
Chroma 3nm Ha 1.25": 41x600" (gain: 200.00) -15C bin 2x2
Chroma 1.25" Lo-Glow LP filter: 24x300" (gain: 125.00) -15C bin 2x2
 
Integration: 22.1 hours
 
Stacked in AstroPixel Processor and processed in Pixinsight, EZ Processing Suite and Photoshop CC 2021
 
I hope you like them.
 
Emil
 
M81-M82-HaLRGB-22-(watermark).png.thumb.png.08457d9ac6d26003e00f0e61fdae745c.png
 
351451251_M81-HaLRGB-(Crop-watermark).png.thumb.png.b38cebde2f63fce49fa926dda9ffd51f.png
 
1212914095_M82-HaLRGB-(Crop-watermark).png.thumb.png.5deae27a69532bf3166fb87536597523.png
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That's really impressive, particularly being in such light polluted skies.   I've only tried HaLRGB once when I was using DSLR.  I like the way it brings out the nebulae in the galaxies.  It's easy to overcook the Ha in these and oversaturate them in post processing, but you've done a fine job!!

Just for my own education, when you say you used drizzle to crop each galaxy individually, could you provide some more detail on what you did and why.  I'm interested in the process, just not sure what this improves or how you do it?

 

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Looks fab.

I assume you added Ha to the R channel ? If so, what mix did you use, I've got some for M51 & M101 to play with so interested to hear on how you added yours.

 

 

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Really nice, while I admire the skill and dedication that is required to capture the IFN around these galaxies, your flux free images show M81/M82 in all their glory. 


Outstanding.👍🏼

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4 hours ago, craigg said:

used drizzle to crop each galaxy individually, could you provide some more detail on what you did and why.  I'm interested in the process, just not sure what this improves or how you do it

Thank you!

With the ASI294M I have the option of using in the unlocked bin 1x1 mode, giving me a resolution of 8288 x 5644 using the cameras with 2.3um pixels. But in this mode and in combination with my AT106 I would be oversampled at 0.69"/px and my sky and the mount doesn't really allow it.

Because of that I'm using the camera in Bin 2x2 mode with a pixel size of 4.63um and to get that high resolution, which is great for galaxy imaging, I choose to drizzle x2 the stacks, where the linear images are reconstructed  and the resolution is doubled giving me in the end a high resolution image that I can easily crop without loosing any detais.

Drizzle is usually used with undersampled images to get that sweet  pixel scale between 1 and 2"/px, I do it all the time with my widefield setup because I'm imaging at 2.27"/px and drizzling is increasing the resolution, giving me a 1.13"/px pixel scale on the final image.

In order to have a good drizzeled result, the I use high dither between the images in the aquisition process and this is giving me a nice, clean drizzled stack. The drizzle algorithm is different from upscaling the photos because it's reconstructing the whole image, pixel by pixel.

At the moment I'm using Astropixel Processor and in the integration tab, right at the bottom, there is an option to drizzle the stacks. Before I used to do it in pixinsight.

I hope this helps in any way.

3 hours ago, jiberjaber said:

Looks fab.

I assume you added Ha to the R channel ? If so, what mix did you use, I've got some for M51 & M101 to play with so interested to hear on how you added yours.

Thanks.

Yes, I did blend the R with the Ha. What I did is opened a new file in photoshop, same size as the images, added the Red from the RGB, and on top of it I copied the Ha in Lighten mode. Many times the Ha is weaker than the R and to make it pop, I stretch the Ha layer quite a lot while keeping the background dark, even black clipped until the Ha areas are staring to come out on top of the R. I flatten the image and replace the R on a duplicate layer of the RGB photo with the new Ha-R blend, again in lighten more as I did before. The lighten mode will only show the the brighter areas from the new Ha-R blend, which of course will be the Ha regions that we want to add in the RGB image.

I hope this helps.

Emil

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