Cocoon Galaxy (NGC 4490 & NGC 4485) -- Galaxies in Canes Venatici
Halton Arp published an “Atlas of Peculiar Galaxies” in 1966. Most of the 338 galaxies in the
Atlas belong to the realm of big Dobsonian Telescopes under dark skies. But not all.
The Arp objects numbered from 269 to 327 are double galaxies, many of which are currently
interacting with each other. A prime example of one that is within reach of modest-sized
amateur telescopes, under suburban skies, is the Cocoon Galaxy (Arp number 269).
You will get no argument from me that familiarity with the Cocoon Galaxy, as gleamed from
observing with my 18-inch Dobsonian away from the city, provided me with what details to
look for, when attempting to draw these two galaxies using my 6-inch refractor from the
backyard. At magnitudes 9.8 & 11.9 and separated by 3.5 arcminutes the pair needs a
good transparent night to tackle in the refractor. The early morning on Valentine’s Day, after
the moon had set, was perfect.
The brighter and larger of the galaxy-pair, NGC 4490, stood out well at 109x magnification;
showing a distinct nucleus in the elongated spiral-galaxy. The smaller and dimmer NGC 4485
was also not difficult but took a little bit more effort to see (a magnitude 12 galaxy is really
pushing the limits in the refractor from the backyard). The real challenge was to make out the
Tidal Warp in NGC 4490 that is directed towards NGC 4485. I was surprised that it also could
be seen using the refractor – but having said that -- it was not without some effort and time at the