NGC/IC Objects

Abell 31: Planetary Nebula (Cancer) RA: 08h 54.2m / DEC: +08° 54'.0
Instrument: 18-inch Obsession

I'm not sure who coined the phrase, but it's been said of the Abell planetaries that they are, "an exquisite form of retinal torture." When it comes to Abell 31, truer words have never been spoken. It's large, about 16'.2 across, and faint, having a photographic magnitude of 12.2. Those numbers give this planetary a surface brightness of 26.9 magnitudes (P) per square arcsecond. Some observers walk away from a bout with Abell 31 claiming nothing more than a sighting of the 15.5 magnitude central star. I didn't get the central star--I don't think I did, anyway--but was able to get the nebula.

My sketch records a 109X view through an OIII filter in the 18-inch Obsession. Abell 31 covers a 14'x9'.5 oval area. This is the central portion of the planetary, which is brighter than the remainder. Images reveal a circular 16' diameter nebulosity that extends just beyond the 9.9 magnitude star west of the planetary's edge in my sketch. This 9.9 mag. star forms a parallelogram asterism along with a 10.1 mag. star (10'.5 to the north), a 10.2 mag. star (15'.3 to the northeast) and the 10.1 mag. star at the center of the planetary in my sketch. Another 46 stars dot the field. You'll find this challenging object about halfway between 4.6 magnitude Alpha (65) Cancri and 3.4 magnitude Epsilon (11) Hydrae.

Abell 30 Abell 33


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Revised: March 13, 2005 [WDF]