The Whirlpool (M51)
Face-on spiral galaxy
aka M 51, NGC 5194, Arp 85, PGC 47404, MCG 8-25-12, UGC 8493
RA: 13h29m52.4s, Dec: +47°11'41" (2000) in Canes Venatici
Galactic lon: +104°51', Galactic lat: +68°34'
Magnitude: 8.90
Size: 9.8'x 6.8'
Mean Surface Br. 22.1 Mag/arc-secē

Minimum requirements to detect: binoculars under dark skies


The Whirlpool galaxy is one of the most photographed and recognizable objects in the sky. It is also a good target for visual observation in any size telescope. This pair of interacting galaxies lie about 20 million light years distant.

In 6-inch or smaller scopes M51 appears as a large, round, hazy spot with a large, slightly brighter center. A much smaller hazy spot lies nearby, nearly touching. This is the companion galaxy, NGC 5195.

Larger aperture telescopes (> 8") will reveal the famous winding spiral arms and connecting bar between the two galaxies on excellent, dark nights. One night in March 2000 I observed M51 in my 18-inch Dob when the sky was very dark. The contrast was excellent and the galaxy beared magnification well. In my 4.8mm Nagler (430x) the main galaxy filled the field of view. The arms were obvious, offset by distinct dark regions between them that were so wide you could drive the proverbial truck through!


The view in an 6-inch at 50x.

This image from the DSS has been processed to approximate the view in a 12-inch or larger telescope on a very dark night. North is down and east is to the right.
Millennium Star Atlas Vol II Chart 589
Sky Atlas 2000 Chart 7
Uranometria 2000 Vol I Chart 76
Uranometria 2nd Ed. Chart 37
Herald-Bobroff Astroatlas B-09 C-11

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