The Wonders of Monoceros in Hydrogen Alpha – 18th January 2024

The Monoceros Region in Hydrogen Alpha

My first image of a new year continues the widefield run I’ve had recently, and I decided to go with a region that has a shedload to offer, and which I’ve imaged several times in far closer crops. Capturing with the Samyang 135mm and the Atik 383L+ Mono with a Hydrogen Alpha filter, this is the region to the northeast of Orion, and is an area awash with star-forming goodness.

The main objects are the Rosette Nebula (Caldwell 49) and NGC2264 – a complex that includes the Cone Nebula and the Christmas Tree Nebula. I’ve captured the Rosette on many an occasion, but never in context as part of the wider complex.  This is about 4hrs 15min of 5 Minute subframes in the hydrogen alpha (far-red) wavelength.

Starless Version

It was captured with NINA at f2.8 on my Samyang 135mm, this time using the larger chip of the Atik 383L+ Mono CCD rather than the Player One one-shot-colour camera.  The Atik has a larger chip compared to the   Stacked and initial processing done in MaximDL, then post-processed in various tools, including Starnet++, Graxpert, Photoshop CC 2024, Lightroom Classic 2024, and Topaz Denoise, amongst others.

This is the widest single field of view available to me at the moment with my kit, and measures a good five degrees or so across. It’s an area that really benefits from being captured in mono Ha, as the detail visible, especially in the starless image, is simply stunning.

Hubble’s Variable Nebula

There’s a nice little bonus in this field of view – NGC2261, or “Hubble’s Variable Nebula” is a fascinating object, very small in this view, but with a very interesting property.  The star that illuminates this nebula is a variable, and as it changes brightness over periods of a few weeks, it causes ‘ripples’ in the brightness of the illumination, which are propagating out (obviously at the speed of light!), but can be seen, as the object itself is still several light years in length.

More info about this phenomenon can be found on it’s wikipedia page at

Particularly interesting is a GIF that shows the ripples.  This small animation was captured over the course of about a year by multiple imagers in a sort of crowdsourcing effort… It’s amazing how amateurs can contribute to this field of science!

Capture and Processing Information - Monoceros Region

  • Object – Caldwell 49 (The Rosette Nebula)  and NGC2264 The Cone and Christmas Tree Nebula Complex.
  • Constellation – Monoceros
  • Camera – Atik 383L+ Mono
  • Exposure – 4hr 15min of 5-min subs
  • Lens – Samyang 135mm f/2 ED UMC
  • Filter – Astronomik Ha CCD
  • Mount  – Skywatcher HEQ5 with Rowan Belt Mod
  • Guidescope – Altair 60mm Finder-Guider
  • Guidecam – SX Lodestar
  • Guide Software – PHD2
  • Capture Software  – NINA
  • Stacking and Initial Processing – MaximDL
  • Post-Processing – MaximDL, StarNet2, Topaz Denoise, Photoshop 2024 and Lightroom Classic 2024.

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