Abell 2 & Abell 3, 20 September 2009
The Deep Sky Section of the BAA is running a project to observe planetary nebulae catalogued by George Abell in 1966 . (The reference enables the full catalogue to be downloaded, including pictures and location maps.) The objects listed are generally very faint and were discovered on images taken with the 1.2 m Palomar Schmidt Camera as part of the Palomar Observatory Sky Survey (POSS). The catalogue lists 86 objects, but several are plate faults or galaxies, some are exceedingly faint, well beyond what I could hope to image, and still others are too far south to observe from Suffolk. But there remain 25–30 planetary nebulae which could potentially be observed from Suffolk, presenting a challenging project!
On 20 September 2009, I imaged Abell 2 and 3. Both are in Cassiopeia so well placed at this time of year. The images illustrate the main features of the nebulae and demonstrate how small and faint they are. The catalogue lists Abell 2 as magnitude 14.5 and just 33x20 arcseconds, i.e. smaller than the disc of Jupiter, and Abell 3 as magnitude 16.0, and clearly larger at 60x60 arcseconds.
Incidentally the star identified in the full-scale image of Abell 3 is a suspected variable and is much brighter in my image than in Guide 7.0 planetarium software. I’m trying to find out more about it...