Arp 263

Arp 263 2016 Apr 6

Object:     ARP 263    (NGC 3239) Date:               2016 April 6
Peculiarity:    Irregular clumps.
Constellation:           Leo Time & altitude:  22.15 UT        54º
Catalogue data: Seeing (5 high):                               4/5
            R.A:                10h 25m Transparency (5 high):                   4/5
            Dec:                +17º 10 Telescope:     0.5m f4.1 Dob.
            Magnitude:    11.4 Eyepiece:      8mm Ethos      x260
            Galaxy size (mins):  5 x 3 Filters:            None


 Taken with Arp 7 seen an hour earlier, these two galaxies demonstrate how surface brightness affects visibility. Arp 7 is 14.5m and tiny while Arp 263 is 11.4m but large. Arp 7 was easy and obvious despite being low in the sky while Arp 263 needs AV to see much at all, even though better placed. A 9th magnitude star is superimposed on it and is a distraction. It is hard to trace the halo’s extent and edges. It is irregular and seems to wrap around the star.  A brighter knot could be made out to the N of the star and another smaller knot, which may be double, lies to the E.