rodelaet
(Post Laureate)
04/22/08 05:43 PM
Attachment
Binocular Icon 7 : M101, a tenuous face-on galaxy.

The first sighting of M101, a large face-on spiral galaxy, was reported by Pierre Méchain in 1781. Charles Messier described M101 as a large, faint nebula without a star. He noted that the galaxy disappeared when he illuminated the crosshairs of his scope.
While M101 is easy to locate, it is a difficult test object for small binoculars. You can star hop from Mizar, following a chain of four 5th and 6th magnitude stars to the southeast. Now put the 4th star in the southwest corner of the field of view. M101 should appear near the centre of the binocular field of view. I find M101 hard to see under a mag 5 sky. Averted vision is needed to glimpse the faint glow of this galaxy. It is my impression that the glow is slightly oval. The listed magnitude of 7.9 has deceived many observers who attempted to find the galaxy with small scopes. The surface brightness of M101 is 14.8. Dark skies are mandatory to enjoy the view of this face-on galaxy in a small scope or a pair of binoculars.


Observing data:
Date : April 11, 2008
Time : around 23.30UT
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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