M42 The Orion Nebula

The Hunter Becomes The Hunted

Continuing our tour of the Orion Constellation in our series “The Hunter Becomes The Hunted”, we come to the Great Nebula in Orion, or Messier 42.

Messier 42, or NGC 1976, or The Great Nebula in Orion

M42 is one that needs very little introduction to astronomers and astrophotographers. Located south of the three bright stars of the asterism Orion’s Belt (Alnitak, Alnilam and Mintaka) it is visible to the naked eye in most locations, although it looks much like a fainter star itself. It’s not until you grab a pair of binoculars that you can start to see some of its nebulosity, showing as a fuzzy patch around a brighter core.

Along with the Pleiades and the Andromeda Galaxy, it is perhaps the most photographed of deep space objects. It is also a tricky one to get right when processing. The bright core of the Trapezium is easy to blow out and lose any details. And yet wanting to capture the surrounding nebula means having to get a decent amount of exposure time. High ISO or gain will get you the latter with ease, but that will blow that core out.

History

There is speculation that the Mayans used the Orion Nebula within their “Three Hearthstones” creation story. If they did then it would certainly appear to correspond to Rigel and Saph at the bottom, with Alnitak at the top, and the smudge being Orion’s Sword (including the nebula) in the centre of an almost equilateral triangle.

I love the ancient stories around the deep space objects. The Mayans, the Egyptians, Romans, Greeks, Native Americans, all have their own ones, some of which are quite similar. Why is that? Why do our elders, who often lived on completely different continents, have so many similar stories about the night sky?

Previous Attempts

I’ve had so many attempts at this one in the years I’ve been an astrophotographer, that I’ve lost count, each one marginally better than the previous as my capture and processing methods have slowly but steadily improved.

My first serious attempt at M42 was at an eye-watering ISO 5000 on a stock Nikon D5300 at 220mm. For a first go, it was actually not bad

I find it’s sometimes easy to become a little complacent with this one. Because it’s so easy to image due to its brightness, we can get away with not putting as much time into it as it deserves. Less than an hour will get you a decent amount of nebulosity and a touch of the darker surrounding dust cloud.

This is a mere 45 mins at ISO 800 with the 72ED and stock 60D

Personally I quite like the slightly wider field of view with my setup using a DSLR as you can also capture both M43 and the Running Man Nebula. Although using the ZWO ASI178MC brings the nebula much closer, I find it to be not quite so striking. I do rather like the colours with the 178 though.

50 mins with the ZWO ASI178MC at 270 gain brings the nebula closer, and you can capture some detail around the Trapezium and also nearby M43 (lower right)

Shooting with the modded 450D can also yield some reasonable results as well. Its higher sensitivity to the red part of the spectrum means being able to better capture that hydrogen within the nebula, again at quite modest settings, and with the 72ED maintaining the wider field of view, and closer to the similar colouring of the 178MC.

Almost 80 mins with the modded 450D and 72ED at ISO 800. Perhaps a little softer in appearance, it highlights my need for an IR filter to better manage the inherent star bloat typical of a modded DSLR.

Whatever I’ve imaged it with though, I’ve found that keeping the exposure times quite short (30 seconds) will help in keeping the core, or the Trapezium, “tamed” so as not to blow it out and lose too much detail. The downside is that you need more time if you REALLY want to go for the detail in the nebula and surrounding area. I have yet to put more than just over an hour into it, mainly in part because of my own complacency I mention above. Let’s face it, there is literally so much space to photograph, when do we decide to stop on an image?

My final(?) attempt for late winter 2022 (February) had me stacking, editing, restacking, re-editing so many times that I lost count. Although it was only 105 minutes, the background dust surrounding M42 was coming through quite nicely, even if the stretching of the data was quite aggressive. Unfortunately I didn’t shoot flat frames for this so a lot of my post processing time wastaken up with sensor blemish removal.

105mins at ISO 400 using the modded 450D at 250mm f/5.6 This is cropped quite closely

The Orion Nebula is a popular destination for astrophotographers, and because of its ease, is one we return to time and time again, often many times in a season. What this means is that you can expect to see me imaging this one plenty more times, and each time will add more and more overall data. So keep your eyes open!

Update 27 Feb 2022

Well I managed to get another run at it before the end of the season thanks to some clear skies that I wasn’t expecting. I’m now a lot happier with this although I can’t wait to add even more to it to bring out that dust around the nebula itself.