NGC 2371/2372 = PK 189+19.1 = PN G189.1+19.8
RA: 07h 25m 33.8s
DEC: +29° 29' 18"
Type: Planetary Nebula (bipolar)
Size: 74"x54"
Mag: V ≈ 11.2

William Herschel discovered this unusual planetary in 1785 with his 18.7-inch speculum reflector and reported a double nebula, resulting in two NGC designations. On March 12th 1785 (his 385th sweep) he described "Two [nebulae]. Faint, of an equal size. Both small within a minute of each other; each has a seeming nucleus, and their apparent atmospheres run into each other. 240x showed the same position from south-preceding to north-preceding." He published a sketch in an 1811 paper as an illustration of "double Nebulae with joined Nebulosity."

In February 1827 John Herschel called NGC 2371 "the south-preceding of a curious bright double neb or an elongated bicentral neb; nuclei approaching to stars 45° nf or sp - distance of centre 60"." In December 1848 Lord Rosse made a sketch using his 72" and found a "bright star between, tails and curved filaments, perhaps an annulus round the two nebulae."

Based on a Crossley photograph, Heber Curtis (1918) described NGC 2371-2 as follows: "Brightest portion consists of two lobes which together form an irregular and patchy oval. The brightest part of these lobes are 35" apart in pa 65°; the toal diameter in this direction is 54". Two very faint, curved outliers are each 60" distant in the prolongation of the major axis in pa 126-306°. A narrow vacant lane runs between the lobes, nearly in the major axis, and widens to include the central star."

NGC 2371/72 is an excellent example of a bipolar planetary, with two symmetric lobes straddling a hot central star. In fact, it's a bit surprising this excellent planetary hasn't been featured before in an OOTW!

NGC 2371.jpg

A 4-inch scope reveals a small, hazy patch 3° southwest of Castor while an 8-inch will resolve Herschel's twin bubbles. In my 18-inch, the bright lobes slant southwest to northeast and both span 15" to 20" in diameter. At 380x unfiltered, the southwest lobe appears brighter and the faint 14.9-magnitude central star is visible at the midpoint. A weak bridge of nebulosity connects the two lobes giving a "dog bone" appearance and a halo encases the structure.

Through my 24-inch, two detached ghostly "polar caps" or ansae can be glimpsed 1' northwest and southeast of the central star, on a line perpendicular to the major axis of the two primary lobes. In excellent conditions the outer wings are barely visible through an 18-inch scope, though the northwest wing is a bit brighter and may be the only one seen.

Back in April 2011 I was wowed by the view through Jimi's 48-inch. Here are my notes --

There was so much intricate detail in NGC 2371/72 it had little resemblance to previous views through my 17.5" and 18" scopes. The most prominent feature was two, irregularly round, very bright nodules on the southwest and northeast side of the boxy, elongated central region. Each nodule was distinctive and varied in surface brightness and shape with the southwest lobe brighter. Filamentary streamers or a "hairy tail" extended from the northeast node towards the northwest and similar wisps extended mainly southeast from the southwest node, creating a sense of rotation around the fairly bright central star. The interior and sides were filled with much fainter nebulosity. A very faint filament connected the main lobes on the northwest edge. Detached from the main 1' structure were two amazing outer wings, symmetrically hanging 1' NW and 1' SE from the central star. These wings or "polar caps" were easily visible without a filter at 488x and both extended ~40"x10" in a SW-NE orientation, increasing the total diameter of the planetary to 2'. A mag 13.5 star lies 1.5' NW and a mag 16 star is 50" NE of center.

This HST image reveals interior details and jets in the main lobes (the elongated pink knots), which were ejected symmetrically from the central star. The brighter one may be visible as a brighter spot in the main southwest lobe.

NGC 2371_HST.jpg

Give it a go and let us know!