Autumn Planetaries

- by Doug Snyder

These observations were made most recently using a 20" f/5 scope under relatively dark skies (limiting magnitude usually about 6.5), but many of the objects can be viewed with smaller instruments with good optics. Observing note applicable for anyone trying these objects (and for observing in general): Use a black shroud or towel to cover your head and the eyepiece while you are viewing. This prevents stray light from entering into your eyepiece, causing reflections and significantly reducing the contrast!

Minkowski 2-51 in Cepheus
22h 16m 05s, +57d 28m.
Size: 47"x38"; Magnitude: 13.6

Located within a moderately crowded star field, this planetary is fairly easy to locate using direct vision without the initial use of a filter. At first glance, it may appear small and circular, but definitely non-stellar. It has a surface brightness of around 12.8 magnitudes/sq. arcminute, and appears slightly oval at lower powers. At higher power and with the use of either an O-III (preferred) or UHC filter, the PN's visibility is enhanced and the extended shape becomes more obvious, with just a hint of darkening towards the center. The central star is not visible. Detecting the faint outer lobes is a real feat. High power; dark and transparent skies and very good seeing are absolutely necessary. There is a mag. 5.9 star (SAO 34256) about 16' SSE of the PN and another fainter, and smaller PN (M2-52) 36' to the east.

Abell 79 in Lacerta
22h 26m 16s, +54d 50m
Size: 59" x 49"; Magnitude:15.3

A pretty difficult object to locate in a field made up of many faint and scattered stars. Once the field is identified, use of an O-III filter from the get-go is necessary. Depending on the conditions, it might be barely visible with direct vision, but more likely you'll have to use averted vision. Its surface brightness (15.0) is almost identical with its magnitude. It will appear as a small disc, smaller than its catalog size listed above, and the central star will not be visible, although it is 'straddled' by two stars around mag. 13. Lower powers (100x to 150x) seem to work well, but the PN does not take well to high power. The biggest challenge I found was in identifying the field!

NGC 7293 in Aquarius
The Helix Nebula

22h 29m 38s, -20d 50m
Size: 880" x 720"; Magnitude: 7.6

One of the finest and largest PN's in the sky at about 15 arcminutes in diameter. Although the listed magnitude is 7.6, its surface brightness is 13.2 magnitudes/sq. arcminute, but it is still quite visible with direct vision and without any filters. At low power and using an O-III filter, this annularly shaped ancient showpiece puts on quite a display. Along with many variations in brightness both in the interior and along the rim, the mag. 13.4 central star is quite distinctive, as are many field stars that lie superimposed along the annulus. Switching to a higher power, say around 200X - 300X, it is quite a trip to follow the east and west extensions out to where they blend into the background as there are many faint filaments in these regions of the Helix.

NGC 7354 in Cepheus
22h 40m 20s, +61d 17m
Size: 28" x 20"; Magnitude: 12.2

With a surface brightness of 10.2 magnitudes/sq. arcminute, this 'pearl' resides in a nice field and is easily seen without the use of a filter, as it is compact and bright. At 212X, there seem to be few variations in the brightness of the disc, but at higher powers and with a filter, subtle variations are quick to be seen. There is some elongation of the PN disc in the north - south direction, as the outer lobes (which would make it appear more circular) are extremely faint and visually overwhelmed by the main shell. There is a mag. 15.0 central star, but its visibility is questionable.

IC 1454 (Abell 81) in Cepheus
22h 42m 24s, +80d 26m
Size: 34" x 31"; Magnitude: 14.4

This miniature ring nebula (as it appears in photographs) has a close stellar neighbor: a mag. 6.8 star only 4 arcminutes to the east. This star helps to identify the location of the PN, but is slightly distracting. The planetary will appear as a disc of about 30", and I believe that any evidence of the ring structure will be visible only with high power and on nights of excellent transparency. The PN takes high power well with a filter, with the UHC filter coming out on top as the filter of choice. With a surface brightness of 12.6, it is easier than the visual mag. of 14.4 would suggest. The mag. 18.6 central star is not visible.

NGC 7662 in Andromeda
The Blue Snowball

23h 25m 54s, +42d 37m
Size: 32" x 28"; Magnitude: 8.3

Exhibiting a pleasing bluish-green glow, this small and bright planetary will surprise many observers who go beyond admiring its color and study its appearance more closely. At high powers, which this PN takes well, one can begin to see more of the small ring structure and the brightness variations between the central core and the innermost shell. By combining an O-III filter and high power, these effects are more pronounced, and even without a filter, a second faint shell can be ascertained that also shows subtle structure and continued evidence of its softly glowing excitation. The central star, at mag. 12.7, is difficult due to the overall brightness of the PN, and can be glimpsed best at high power and without a filter.

Jones 1 in Pegasus
23h 35m 53s, +30d 28m
Size: 314"; Magnitude: 12.1

In properly oriented photographs (north up), this large and faint planetary appears as a backwards 'C'; needless to say, if you are not under dark skies, you will not 'C' it! The surface brightness for Jones 1 is 16.6 magnitudes/sq. arcminute. The brightest portions of the object are the north and south 'arcs' of the 'C'. The area between the two arcs is very dark, showing no hint of nebulosity. The region on the western side of the nebula which connects the two arcs is significantly fainter, but still visible using averted vision. The use of an O-III filter is usually required, but there are nights when portions of the arcs can be glimpsed without a filter when the exact field location is known!

Abell 84 in Cassiopeia
23h 47m 43s, +51d 24m
Size: 147" x 114"; Magnitude: 13.0

The many stars in the field make it difficult to pinpoint the exact location of this planetary, but perseverance and the O-III filter finally paved the way. This PN, being moderately large, and typically a faint Abell object, does not take high power well. I used about 100X to study the field without a filter, then progressed to 149X and the O-III to find Abell 84. With a surface brightness of 14.67, it is not terribly difficult, but the brightness variations around and in the oval-shaped object tend to make it appear more irregularly-shaped and without much structure. On most occasions, it is viewable with direct vision, but averted vision allows more of the annular shape to be seen. The brightest portion is a segment, not quite arc-shaped, on the east side, where there is also a mag. 10.7 star. As an aid in locating the field, there is a mag. 7.9 star (SAO 35757) about 13' SSW of the planetary.

IsWe2 in Cepheus
The Senile Nebula

22h 13m 23s, +65d 54
Size: 900" (15'); Magnitude: Unknown!

An ancient, huge, and faint planetary that was discovered on the original POSS plates in 1986, this is one tough observation! Its age is estimated at around 40,000 years (very old and decrepit) and its distance at roughly 847 light years. Lying in a relatively quiet neighborhood of Cepheus, the planetary is nicely framed by a trio of bright stars which fall within a one degree circle. These three stars are of magnitudes 7.1, 7.7 and 8.0, and form an almost perfect equilateral triangle, with the PN nearly centered within this triangle. The best method of attack is to use very low power (80X to 100X), an O-III filter, and a dark shroud to cover the head and the eyepiece. Any external light or reflections entering the eyepiece will most likely render an attempt fruitless.

Although the PN is oval-shaped and elongated in a NW - SE direction, the region that is first glimpsed through the eyepiece is an arc of ejected material that lies on the NE portion of the shell. During moments of excellent seeing and transparency, the fainter portion of the arc to the north may also be detected. In the field image here, the brightest star in the field is mag. 9.5 and lies at the NW edge of the nebula.This is the first known visual sighting of this planetary. (IsWe1 in Perseus at 03h 49.1m, +50d 00m remains undetected visually.)