Telescope Reviews: Binocular Icon 5 : M51, the Whirlpool Galaxy

During this time of the year, Ursa Major and Canes Venatici rise high in the sky. It's a perfect time to take a look at M51 (which belongs to Canes Venatici).

When Charles Messier chanced upon the Whirlpool Galaxy in the night of 13 October 1773, he only saw the core of NGC 5194. It was Pierre Méchain who first made note of the companion galaxy NGC 5195 in 1781. Since then M51 is called a double object. M51 is also the first galaxy in the history of the astronomy that showed a spiral structure. It was Lord Rosse who resolved the nebula of M51 into a spiral system, at Birr Castle in Ireland with the giant 72” reflector in 1845. Famous are Lord Rosse’s sketches of this fabulous galaxy.

At a distance of 27 million l-y, M51 shines at magnitude 8.4. This whirlpool of stars has some challenges to offer for any kind of scope, even for small binoculars!

M51 is easily found, at 3.5° SW of Alkaid (Eta Ursa Majoris). The galaxy forms the fourth corner of a little trapezium together with three faint stars. Try to keep Alkaid at the border of the field of view, and M51 should be visible near the center of the binocular field. At first only a fuzzy patch is apparent. A closer look reveals that the patch is really elongated in a roughly N-S direction. With time and patience, I could detect the cores of NGC 5194 and NGC 5195. It was as if two tiny eyes were looking at me from outer space. Here is where the sweet spot of the retina plays a major role. I’m still experimenting with it. The use of both eyes is a new exercise for me. And the sweet spots do not merge with each other! The core of NGC 5194 was brighter, while the other was difficult to see. The core of NGC 5195 could be compared with a star of mag 9.5, which is also the limiting magnitude I can reach with the 8x56. I had the impression that the area between the two cores appeared slightly brighter, compared to the rest of the galaxy. While this observation was a surprising exercise with a mounted pair of binoculars, I can imagine that a fair amount of details would be missed when holding the binoculars free-handed. The bright star at the left border of the sketch is Alkaid, Eta Ursa Majoris.

Observing data:
Date : April 11, 2008
Time : around 21.30UT
Binoculars : Bresser 8x56
FOV: 5.9°
Filter : none
Mount : Trico Machine Sky Window
Seeing : 3/5
Transp. : 2.5/5
Nelm : 5.0
Sketch Orientation : N up, W right.
Digital sketch made with PhotoPaint, based on a raw pencil sketch.

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Rony

My Astronomical Sketches

My Binocular Sketches

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Edited by rodelaet (04/15/08 04:35 PM)