Deep-Sky Tour

See the clus­ters and nedu­lae that fill the sky around Orion’s belt

Sky at Night Magazine - - CONTENTS -

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

NGC 2024, NGC 2023 and B33, the Horse­head Ne­bula, form a line run­ning un­der bright Al­ni­tak

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