Messier 81

81 final

Object:   M81 (NGC 3031) Date:               2019 March 29
Type:              Spiral galaxy
Constellation:           Ursa Major Time & altitude:          21.30 UT   72º
Catalogue data: Seeing (5 high):                               4/5
            R.A:                9h 56m Transparency (5 high):                   3/5
            Dec:                69º 04 Telescope:     0.5m f4.1  Dob.
            Magnitude     6.8 Eyepiece       17mm & 8mm Ethos                                    x120 & x260
            Size (mins)    26 x 14 Filters:            Lumicon Deep Sky


Spent more than an hour inspecting M81 in average conditions. Naked eye limiting magnitude is about 5.0m. There is some ground mist aggravating light pollution.

I could not detect any sign of the spiral structure. There is a bright, smooth, oval core embedded in a grainy inner halo. Beyond this, is the faint outer halo. The size of the outer halo is difficult to quantify as it fades out to the sky background. Measuring from the sketch indicates I have traced the halo for 17 – 18 arcmins. The better view of the outer halo was with the 17mm eyepiece at x120. Using the Lumicon filter improved the view of the outer halo at x260, making it comparable to the unfiltered view at x120. In addition I was able to pick out a faint star close in on the NE side of the core.