Arp 26

Arp 26 2019 Feb 25

Object:   Arp 26 (M101, NGC 5457) Date:               2019 February 25
Peculiarity:  Spiral with one heavy arm.
Constellation:           Ursa Major Time & altitude:        23.50 UT     56º
Catalogue data: Seeing (5 high):                               3/5
            R.A:                14h 03m Transparency (5 high):                   4/5
            Dec:                54º 21 Telescope:     0.5m f4.1  Dob.
            Magnitude     8.3 Eyepiece       17mm Ethos              x120
            Galaxy size (mins)   29 x 27 Filters:            None


The spiral structure is not obvious as it is with e.g. Arp 85, M51. The whole thing is low surface brightness and one is picking out indistinct arcs which have little contrast to the background glow. There are no dark lanes but there are some bright knots, HII regions with their own NGC numbers.

The non-stellar nucleus is bright and round. A 12th mag. star is close by on the N side. The nucleus sits at the W end of an irregular halo. The HII region NGC 5461 is easily visible with DV. NGC 5462 is more difficult, seen on and off with AV. NGC 5447 is midway between the two in difficulty.

On the E edge of M101 the galaxy NGC 5471 14.7m 0.7×0.6 mins, was visible with DV as a round fuzz. Further out in the same direction I was not able to see NGC 5477 14.0m 1.8×1.3 mins.On the W edge is galaxy PGC 49919 14.9m 1.0×0.5 mins, seen and held with AV.

Because of the size of, and detail in, this object, exceptionally I used a Megastar chart with stars to 14.0m as a starting grid to prepare the drawing, instead of plotting all the stars from scratch.