M51 – The Whirlpool Galaxy – March 2019

M51 – The Whirlpool Galaxy – LRGB with Added Ha

Another image captured a while back, but only now posted, this is an LRGB (Luminance, Red, Green, Blue) image of M51 – the Whirlpool Galaxy in Canes Venatici.

It consists of 1hr each of Red, Green and Blue, and 2hrs of Hydrogen Alpha – all in 5min subs, along with 2hrs of Luminance taken through a CLS filter.  It was taken across several nights in March 2019 (spread across about two weeks!), and from several different locations. It was stacked and put through DDP (digital development), along with RGB combination in MaximDL. It was then exported to Photoshop CC 2018, combined with the Luminance, and the was Ha added into the red channel to bring out the lovely H2 regions (the little red dots on the galaxy – areas of high star formation – stellar nurseries). As Susan, lots of other fiddling and tweaking was followed by export to Lightroom CC Classic for the final touches.

M51 – Luminance Only

It was captured with the Atik 314L Mono, through the Altair 102ED at f/7 using Astronomik 12nm Ha, Astronomik RGB, and Altair CLS Filters. Mounted on HEQ5 and guided via OAG with SX Lodestar guide cam.   The initial capture was actually the luminance data, which I actually love all on it’s own.  The colour is really worth going for in this case, but I’ve included this mono luminance image to show that sometimes it’s really worth the effort of capturing that first, as it stands alone even if you don’t manage to add the colour data until a later time.

I particularly love this galaxy.  It’s one of the classic ‘Galaxy’ galaxies (if you see what I mean!).  The smaller portion off to the left is actually a totally separate galaxy that has collided with the main one, going sort of ‘into’ the plane of the image, and it’s actually the smaller one that’s pulling off material from the main spiral.  This process is very slow, taking place over millions of years, but eventually, the two galaxies will merge to form one giant elliptical galaxy with no real noticeable structure.

As usual I’ve included the detailed capture info below.

Capture and Processing Information

  • Object  – Whirlpool Galaxy (Messier 51)
  • Constellation – Canes Venatici
  • Camera – Atik 314L Mono
  • Exposure RGB – 1hr in 5min subs
  • Exposure Ha – 2hrs of 5min each
  • Exposure Luminance – 2hrs of 5min Subs
  • Filters – Astronomik 12nm Ha, Baader 7nm OIII, Astronomik RGB, Altair CLS-CCD
  • Telescope – Altair 102ED Refractor
  • Mount  – Skywatcher HEQ5 with Rowan Belt Mod
  • Guidescope – Off-axis
  • Guidecam – SX Lodestar
  • Guide Software – PHD2
  • Auto-Focuser – Home-Made MyFocuserPro2 Autofocuser
  • Capture Software  – Sequence Generator Pro
  • Stacking, RGB Combination, and Initial Processing – MaximDL
  • Post-Processing – Photoshop CC and Lightroom CC.


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