M35 is a fantastic open cluster located in the constellation of Gemini. At magnitude +5.2, it's visible to the naked eye under good conditions. Curiously, despite being a naked eye object, it wasn't discovered until 1745-46 by Philippe Loys de Chéseaux and then independently "re-discovered" by John Bevis sometime before 1750. Since the cluster is reasonable close at 2,800 light-years it presents a large apparent diameter of some 28 arc minutes - almost exactly the same as that of the full Moon. Without a doubt, M35 is a magnificent sight in all types of optical instruments.
The constellation Gemini covers a reasonable 514 sq. degrees and is partially located in the rich star fields of the Milky Way. During the winter months, it's positioned high in the sky for Northern Hemisphere observers although less well placed for those located further south. Surprisingly, despite such a prime Milky Way location, M35 is the only Messier object in Gemini. It's located at the western edge of the constellation in a corner of the sky close to the Taurus, Orion and Auriga borders. Finding M35 is quite easy as it's 3.5 degrees northwest of mag. +2.9 star, Mu (μ) Gem.
To the naked eye, M35 appears as a misty patch that's easier to spot with averted vision. Through 10x50 binoculars, the brightest dozen or so stars are resolvable. The grouping appears tight, surrounded with haze and shaped like an oblong. With larger 20x80 binoculars, M35 appears spectacular with much of the mist seen in smaller binoculars now resolved into stars. An 80mm (3.1 inch) telescope reveals many bright and some faint stars spread evenly across the entire cluster face. Through a 150mm (6-inch) to 200mm (8-inch) telescope at low magnifications, M35 displays a field full of stars with many arranged in chains and lines. A brighter orange star lies towards the centre. In total, it contains a couple of hundred stars of which at least 120 are brighter than 13th magnitude.
There is another fainter open cluster that's located only about 15 arc minutes southwest of M35. This cluster is named NGC 2158 and shines at mag. +8.6. However, it can be spotted in 10x50 binoculars under dark skies. It appears more compact than M35 and is a nice sight when viewed through telescopes. The two clusters are intrinsically similar and the only reason NGC 2158 appears fainter and smaller, is simply because it's five times more distant.
M35 is a wonderful open cluster that can be seen with the naked eye under dark skies. Covering an area of almost half a degree it's a must see object, which is a superb site in all types of optical instruments.
M35 Data Table
|Object Type||Open cluster|
|RA (J2000)||06h 08m 56s|
|DEC (J2000)||+24d 21m 28s|
|Apparent Size (arc mins)||28 x 28|
|Age (years)||100 Million|
|Number of Stars||200|
|Other Name||Collinder 82|