Celestial hemisphere:  Northern  ·  Constellation: Andromeda (And)  ·  Contains:  Andromeda Galaxy  ·  HD3765  ·  HD3969  ·  HD4143  ·  HD4174  ·  HD4322  ·  HD4501  ·  M 110  ·  M 31  ·  M 32  ·  NGC 205  ·  NGC 206  ·  NGC 221  ·  NGC 224  ·  PGC 2159387  ·  PGC 2160264  ·  PGC 2160642  ·  PGC 2160820  ·  PGC 2162367  ·  PGC 2162656  ·  PGC 2163200  ·  PGC 2163634  ·  PGC 2164256  ·  PGC 2166758  ·  PGC 2167368  ·  PGC 2168731  ·  PGC 2168810  ·  PGC 2169318  ·  PGC 2172440  ·  PGC 2174839  ·  And 30 more.
Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
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Messier 31: a 2-panel mosaic in RGBHOO

Revision title: Increased Topaz cleanup

Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
Powered byPixInsight

Messier 31: a 2-panel mosaic in RGBHOO

Revision title: Increased Topaz cleanup

Equipment

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Acquisition details

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Description

I've been wanting to return to the Andromeda Galaxy since upgrading from a 61 ZenithStar 61 APO doublet.

Now that the AstroTech AT115EDT (a fantastic APO triplet) seems to be dialed in, it was the perfect chance to not only return to this beautiful target, but also to try the scope out on a mosaic. At 1.2"/pixel, I can fit a LOT of M31 one in an ASPC frame, but not all of it. This framing has about 20% overlap between the two panels. 

It was also a great opportunity to try out combinations of RGB, Ha, and [OIII]. On night 1, I captured 4 hours (80 x 3 min) on each frame in broadband, no filter. On night 2, I captured 4.5 hours (54 x 5 min) in dual narrowband with an L-extreme filter. 

Ha and [OIII] were extracted and stacked for each panel in AstroPixelProcessor. As usual, I processed light pollution as much as possible in each individual RGB, Ha, and [OIII] panel, then mosaiced each channel separately. (The RGB-only mosaic is in C.) 

I then registered and combined the separate RGB, Ha and [OIII] mosaics, and this is where it gets fun: choices! I looked at HaRGB and RGBHOO. HaRGB (which is a traditional representation for M31) did indeed strengthen the details, but i found that some combinations ended up losing some of the lightness of the outer disk and the connection between M31 and M110. Brining in the [OIII] for RGBHOO struck a nice balance between bringing in more of the Ha nebulas in M31 while keeping the blues and purples of that broader disk. 

The other interesting trial and error was how to combine the channels: add, multiply, add-scale, or multiply-scale. The default setting in AstroPixelProcessor is multiply-scale, but this made the reds far too harsh. (See for example D with light processing.) Add-scale struck a nice balance between the original RGB and the crisper detail of the Ha mosaic. That's what you see here. Overall, this is the best luck I've ever had on M31, and I've learned a lot in the process! 

And truly, this AT115EDT punches far above its weight!

Comments

Revisions

  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    Original
  • Final
    Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    B
  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    C
  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    D
  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    E
  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    F
  • Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin
    G

B

Title: Increased Topaz cleanup

Description: I ended up adding some more topaz cleanup so you can see the gorgeous little galaxies (those small features annotated with cyan PGC's). I set the JPEG level to keep the file size under 20 MB.

Uploaded: ...

C

Title: RGB data only

Description: Here's a mosaic using the first night's RGB data only. I liked the colors on this one, but it shows how much the Ha really helped to bring out the dust lanes and nebulas.

Uploaded: ...

D

Title: HaRGB with multiply-scale

Description: It's nice, and the Ha does indeed "pop"! But I find the reds too harsh, and some light detail in the disk is lost.

Uploaded: ...

E

Title: Ha mosaic

Uploaded: ...

F

Title: [OIII] mosaic

Uploaded: ...

G

Title: Refined color balance

Description: Adjusted color balance due to blueish cast.

Uploaded: ...

Sky plot

Sky plot

Histogram

Messier 31: a 2-panel mosaic in RGBHOO, Paul Macklin