Deep-Sky Tour
See the clusters and nedulae that fill the sky around Orion’s belt
Tick the box when you’ve seen each one
1 NGC 2112
NGC 2112 is a 9th-magnitude open cluster in Orion. It’s positioned behind one section of the gigantic, faint ring of nebulosity known as Barnard’s Loop. The cluster is estimated to be 3,064 lightyears away, around twice the farthest distance estimate of the loop. NGC 2112 lies 4° northeast of mag. +1.9 Alnitak (Zeta
Orionis). It’s fairly rich, containing around 100 stars, many of which are around 12-13th magnitude. This is a rich area of sky, which makes it easy to lose NGC 2112 against the background. Using a low power, a 6-inch scope shows a granulated glowing patch approximately 6 arcminutes across. A 10-inch scope resolves about 35 members against a haze around 10 arcminutes across. SEEN IT
NGC 2071
Head 1.7° west from NGC 2112 and you’ll arrive at NGC 2071. This is an 8th-magnitude reflection nebula located 0.25º northeast of our third target, M78. There is often confusion here as M78 is also a reflection nebula. NGC 2071 is visible in a small telescope as a faint hazy glow. A good strategy when using smaller apertures is to use averted vision, looking slightly to the side of the nebula to place its delicate light on a more sensitive part of your retina. NGC 2071’s glow appears about the same as that of a 10th-magnitude star. Larger apertures show it off-centre with respect to the star, most of the nebulosity appearing to the south. SEEN IT
3 M78
M78 is an easy find from NGC 2017, sitting just 0.25º farther southwest. This reflection nebula is a lovely sight in a small telescope. Listed at mag. +8.3, it appears as a misty glow with two embedded stars of similar brightness. The overall appearance is like that of a car with its headlights on at night, approaching through fog. A 6-inch scope shows an oval shape with a longest dimension of 6 arcminutes. Careful scrutiny reveals a non-uniform brightness, portions of the nebula to the north shining slightly brighter than the rest. When viewed through larger apertures M78 appears to widen towards the southeast, showing a sharp edge to the northwest. SEEN IT
4 NGC 2024
NGC 2024 is enigmatically named the Flame Nebula. It’s large and very detailed, but suffers from close proximity to the bright star Alnitak at the eastern end of Orion’s Belt. The centre of the nebula is 17 arcminutes eastnortheast of the star. A 6-inch scope shows a glowing region bifurcated by a dark line. The easiest way to see detail is to use a low power and place Alnitak out of the field of view. An 8-inch instrument begins to show dark tributaries branching off the central, 3-arcminute-wide dark lane, giving an appearance similar to a glowing leaf. The larger the scope, the more of these dark tributaries can be seen. SEEN IT
5 NGC 2023
There’s another bright reflection nebula close to Alnitak but this one looks completely different to the Flame Nebula. NGC 2023 is 21 arcminutes east-southeast of Alnitak and is relatively easy to see through a 6-inch scope. It surrounds 8th-magnitude star HD 37903, around which it gives the appearance of a mottled glowing cocoon, fading in brightness from the centre out. At around 10 arcminutes across, NGC 2023 is much smaller than the 30-arcminute-diameter Flame Nebula and being circular means it can disguise itself like a star at low magnifications. NGC 2023 is estimated to be four lightyears across, making it one of the largest-known examples of a reflection nebula. SEEN IT
6 THE HORSEHEAD NEBULA
Our final target is the Horsehead Nebula, Barnard 33, and it can be found 28 arcminutes south of Alnitak. This is a finger of dark nebulosity protruding across a brighter curtain formed by emission nebula IC 434. A dark, clear sky and dark-adapted eyes are essential here. The first step in locating the Horsehead is to identify the background curtain of IC 434. Using a low power of around 50x, look for the dark intrusion along its eastern edge between mag. +7.5 HD 37805 and mag. +10.9 TYC 4771-0896-1. A UHC or hydrogen-beta filter will make seeing the dark intrusion easier but don’t be disheartened if you can’t see it – Barnard 33 can be quite challenging. SEEN IT