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NGC 6946 is a marvellously handsome-looking galaxy, with its attractive ‘pinwheel’ spiral construction set in a star-sparkling area for these imagers searching for the prettiest of images. But, it’s additionally of supreme curiosity to science-seeking amateurs {and professional} astronomers alike, with its extraordinary propensity to yield exploding stars. This has led to its very apt nickname of ‘The Fireworks Galaxy’!
The best way to observe
NGC 6946, additionally catalogued as Caldwell 12, is an intermediate spiral galaxy (it has the classification SAB(rs)cd, beneath the Hubble/de Vaucouleurs system) straddling the boundary between the constellations of Cygnus and Cepheus. On August nights it’s splendidly positioned for remark throughout the UK, mendacity nearly on the zenith at midnight BST mid-month, from London.
It’s not a straightforward galaxy to search out as its speedy locale will not be brimming with shiny stars. Attempt ranging from magnitude +2.5 Alderamin (alpha [α] Cephei) after which find eta (η, magnitude +3.4) Cephei 4 levels to the south-west; NGC 6946 lies an extra two levels in the identical route. NGC 6946 is likely one of the closest ‘large’ spiral galaxies past our Native Group (it lies about 22 million gentle years away), so it has a fairly shiny catalogued magnitude of +8.9. Nonetheless, being a spiral galaxy that’s oriented face-on to our perspective, it’s bothered by a notoriously low floor brightness throughout its substantial 11 × 10 arcminute kind, which makes it a troublesome goal for smaller-aperture telescopes.
Deep novice photographs routinely present glittering H-II areas and younger star clusters, testomony to a excessive stage of ongoing star formation. This can be one purpose why NGC 6946 is very prolific at producing supernovae; ten (designated 1917A, 1939C, 1948B, 1968D, 1969P, 1980K, 2002hh, 2004et, 2008S and 2017eaw) have been noticed over the previous 100 years or so!
NGC 6946 ought to be captured visually via a 150mm (six-inch) telescope on a positive evening at a dark-sky location, however don’t count on to see greater than a uniformly-lit diffuse and faint halo. A 400mm (16-inch) aperture could reveal among the H-II areas that liberally dot the galaxy’s a number of spiral arms.
When you’ve had your fill of the galaxy, there’s a pleasant bonus awaiting because the welcoming open cluster NGC 6939 lies simply over half a level away to the north-west. It’s a a lot simpler visible proposition and a positive sight via any telescope. Shining with an built-in magnitude of +7.8 on account of the mixed gentle of maybe 120-140 stars crammed into an obvious diameter of 8’, NGC 6939 is seen in finderscopes on a superb evening. NGC 6946 and NGC 6939 pair make an amazing goal for wide-field imagers.
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