While at Lake Sonoma on Wednesday evening, I spent most of my time poking
around the Fornax galaxy cluster, but I also took a look at a challenging
ancient planetary, Abell 7 in Lepus and the surrounding area. With listed
dimensions of 871"x670", this is one of the largest of the Abell planetaries,
a result of being situated relatively nearby and an advanced age. As
expected, the surface brightness is quite low, so this is not an easy target
unless conditions are excellent. Here's what I recorded in this area on
Wednesday night with my 18-inch Starmaster:
Abell 7 = PK 215-30.1 = PN G215.5-30.8
05 03 08.0 -15 36 13
Size 871"x670"
18": at 73x and OIII filter, this ancient planetary appears as an extremely
large, ghostly glow, perhaps 6' in diameter. Although the surface brightness
is very low, it was visible as an irregularly-shaped, hazy patch involved
with 5 or 6 stars on the south side. The edge of the planetary is better
defined on the southern periphery and appears to fade out on the N side, so I
was probably viewing only a portion of the object. Once identified, though,
it was not difficult with averted vision.
Coincidentally, there's a very faint galaxy, MCG -03-13-058, just outside the
edge of the halo, 10' NW of center! This required some hunting, though, as
it's also a difficult object. And of course, the OIII filter had to go.
MCG -03-13-058
05 02 29.2 -15 32 43
V = 14.1; Size 1.5x0.7; SB = 14.0; PA = 75d
18": extremely faint, fairly small, round, very low even surface brightness,
0.7' diameter, elongation not noticed (probably just viewed the core).
Located ~10' NW of the center of the giant planetary Abell 7 and 5' SW mag
9.9 SAO 150096.
As a bonus, there's a Hickson Compact Group (HCG 32) with brightest member
MCG -03-13-053 just 12' NW of this galaxy! A quick look only netted one
member, but a steadier night might bring out some of the fainter companions.
HCG 32a = MCG -03-13-053
05 01 45.2 -15 26 56
V = 13.4; Size 0.3x0.3
18": extremely faint, round, 15" diameter. Located close following a mag
13.5 star. Visible only half the time with averted vision.
If anyone is interested in going after these toughies, the field of Abell 7
is just 70' SE of Hind's Crimson Star (R Leporis), a great place to start
your visit.
Steve Gottlieb