NGC 2403 (Caldwell 7) is a big, vivid galaxy that serves up good views for small telescopes however it’s place within the moderately obscure northern constellation of Camelopardalis has stunted its recognition. It’s a really photogenic object, with deep beginner photographs revealing a powerful likeness to Messier 33, the magnificent Native Group spiral, albeit on a less-grander scale. A small telescope can monitor it down, whereas a monster light-bucket Dobsonian telescope isn’t required to trace at its construction.
NGC 2403 is an outlying member of the M81 group of galaxies, named for the magnificent spiral galaxy in Ursa Main, which is likely one of the nearest such grouping to our personal Native Group, its centre mendacity roughly 11–12 million gentle years away. NGC 2403’s distance is round 10 million gentle years and its bodily diameter is 98,000 gentle years.
Not like M33, NGC 2403 doesn’t seem face-on to our perspective, the literature giving an inclination of simply 28 levels from edge-on; to me, nevertheless, it seems much less inclined, because the plentiful deep photographs of it out there on the Web present. What NGC 2403 does have in frequent with the third largest galaxy within the Native Group is its morphological classification (SAB(s)cd), and that it hosts greater than its fair proportion of giant star forming HII areas. These aforementioned Web photographs reveal this lovely galaxy’s spiral arms are dotted with their give-away reddish glow. In reality, the galaxy is believed to include round 100 of those monster, energised areas, with a minimum of half a dozen of that are so massive and luminous that they rival our Native Group behemoth 30 Doradus (The Tarantula Nebula), mendacity within the Giant Magellanic Clous, and NGC 604 in M33.
Traditionally, NGC 2403 has performed an necessary function in figuring out the cosmological distance scale; within the Sixties, Allan Sandage, the nice American astronomer who’s credited with the primary moderately correct willpower of the Hubble Fixed and found the primary quasar, detected the primary Cepheid variable stars in a galaxy past the Native Group, when he skilled the 200-inch Hale Telescope on the Palomar Observatory, in California, on NGC 2403. William Herschel found the galaxy in 1788.
Tips on how to observe it
NGC 2403 lies in jap Camelopardalis (Cam), near the boundary with Ursa Main. We will use one of many Nice Bear’s stars to assist us monitor down the galaxy. Ranging from magnitude +3.3 Muscida (omicron [ο] Ursae Majoris), transfer round 5 levels north-west to seek out magnitude +5.9 51 Cam and NGC 2403 lies a mere diploma to the west.
NGC 2403 has a minimum of one benefit of its location in Camelopardalis – it’s circumpolar from mid-northern latitudes, together with the UK, which implies that it’s all the time above the horizon. Within the second half of December, as quickly as true astronomical darkness descends (at about 6pm GMT) NGC 2403 sits round 37 levels up within the north-eastern sky. It peaks in altitude near the zenith within the small hours.
NGC 2403 glows fairly brightly at magnitude +8.4 and pictures present its obvious diameter extending to a considerable 22 x1 2 arcminutes. Beneath an exceptionally darkish and clear sky, you may glimpse NGC 2403’s very faint oval glow by means of 10 x 50 binoculars, however a small telescope will readily snare it. Improve to a 250mm (10-inch) telescope and you may even see some mottling throughout a ten x 3 arcminute space, depicting elusive and tenuous spiral construction.
