Archive for November 19, 2021

NGC 7662 Planetary Nebula in Andromeda: November 2021 Observer’s Challenge Report #154

November 19, 2021


Compiled by:

Roger Ivester, North Carolina


Sue French, New York

November 2021

Report #154

NGC 7662 Planetary Nebula in Andromeda

Sharing Observations and Bringing Amateur Astronomers Together

Work-File: Used only for organization and editing. When all entries are received, a .pdf report will be issued by the 10th of December. And the link will be posted on this page.


The purpose of the Observer’s Challenge is to encourage the pursuit of visual observing. It’s open to everyone who’s interested, and if you’re able to contribute notes and/or drawings, we’ll be happy to include them in our monthly summary. Visual astronomy depends on what’s seen through the eyepiece. Not only does it satisfy an innate curiosity, but it allows the visual observer to discover the beauty and the wonderment of the night sky. Before photography, all observations depended on what astronomers saw in the eyepiece, and how they recorded their observations. This was done through notes and drawings, and that’s the tradition we’re stressing in the Observer’s Challenge. And for folks with an interest in astrophotography, your digital images and notes are just as welcome. The hope is that you’ll read through these reports and become inspired to take more time at the eyepiece, study each object, and look for those subtle details that you might never have noticed before.

This month’s target:

Commonly called the Blue Snowball, the planetary nebula NGC 7662 dwells in the northern reaches of Andromeda. Its nickname springs from an article by Leland S. Copeland in the February 1960 issue of Sky & Telescope magazine. Copeland describes the nebula as “looking like a light blue snowball.” 

William Herschel discovered this nebula on October 6, 1784, with this 18.7-inch reflector. His journal entry reads: A wonderful bright, round planetary pretty well defined disk, a little eliptical [sic]; perhaps 10 or 12″ diameter. Another entry from October 3, 1790, endearingly states: My planetary nebula. A very beautiful object, with a vS [very small] star following; giving one the idea of a large Planet with a vS satellite. In his impressive new book, William Herschel Discoverer of the Deep Sky, NGC/IC researcher Wolfgang Steinicke credits William Herschel with 10 observations of NGC 7662.

William Lassell made this sketch from the view through his 48-inch reflector. It was published in the Memoirs of the Royal Astronomical Society in 1866, in which he also noted the nebula’s bluish color. 

Mario Motta: Observer from Massachusetts

Using NB filters through my 32-inch scope with SBIG STL 1001E camera, cropped and enlarged x 2 as it is a very small sized object, taken with 1 hour each of H alpha, S3, and O2 filters.

Rony De Laet: Observer from Belgium

NGC 7662 (Caldwell 22) is easily recognisable as a bright and slightly bluish planetary nebula in my lowest power eyepiece. But with increased power there is hardly any structure to be seen. Nor is the central star visible. The nebula appears bright but amorphous. I don’t see any improvement with an OIII filter. I move over to my 3mm eyepiece. But even at 600x there is no trace of the CS. Although the limiting magnitude is near 15.2 in that part of the sky, the seeing is not cooperating. Back at 400x things start to look a little better. There is a hint of an central ring or better two opposite arcs: one brighter to the north-east and one dimmer to the south-west. While the arcs seem to connect to the south-east, the north-west side remains open. The core of the nebula appears off-centre due to a slightly darker patch near the open end of the arcs. There is a variety of light intensities within the central part of the nebula. It takes a lot of time to tease out any detail. Now back to the edges of this planetary. They too seem to harbour subtle arcs of light. I switch to 200x and put in the OIII filter. The planetary is embedded a weak elliptical halo, which is twice the size of the planetary.

Site : Bekkevoort, Belgium (51° N)

Date : November 10, 2021
Time : around 20:30 UT

Telescope : Taurus 16”
EP: Morpheus 9mm 76°, 200x / 6.5mm 76°, 280x / 4.5mm 76°, 400x / Omegon 3mm 55°, 600x
Filter : OIII or none
Seeing : 2/5
Sky brightness : 19.7 magnitudes per square arc second near zenith (SQM reading).
Sketch Orientation: N up, W right.
Digital sketch made with Corel Paint Shop Pro X2, based on a raw pencil sketch.

Uwe Glahn: Observer from Germany

Item: NGC 7662 – “Blue Snowball”

Telescope: 20 “f / 4.3 Newton

Magnification: 620x

Filter: /

Conditions: fst 6m5 +

Seeing: II-III

Roger Ivester: Observer from North Carolina

NGC 7662: Planetary Nebula in Andromeda 

Date:  December 25, 1997

Telescope:  10-inch f/4.5 reflector and equatorially mounted

Sketch Magnification:  200x

Field-of-View:  0.25º

Small and bright blue disc, with a brighter more concentrated interior, and with a very faint outer halo.  Very soft edges.  No central star or void could be seen.  This description is very consistent with ten other observations, using the same scope and location, over the past 30 years. No filter was used.  

James Dire: Observer from Illinois

NGC 7662, also known as Caldwell 22 and the Blue Snowball Nebula, is a magnitude 8.2 planetary nebula in the constellation Andromeda.  The nebula lies 14.3 degrees west of the famous Andromeda Galaxy, M31.  The nebula also lies 4.3 degrees east of the star Omicron Andromedae (mag. 3.64) and 2.3 degrees west-southwest of the star Iota Andromedae (mag. 4.28).  The nebula is about 32 x 28 arcseconds in size, making it a challenge to image in small telescopes. But its great surface brightness is splendid for visual observation.

Like most planetary nebula, NGC 7662 formed when the central star began throwing off its outer layers as the star reached the end of its life on the main sequence.  The nebula’s distance is estimated to be around 1800 light years away. Making the nebula about 1.6 light years in diameter.

In small telescopes the nebula may appear star-like at low powers with a slight blue color. Larger apertures at high magnification bring out its planetary nebula nature and its blue color is more striking.  The largest amateur telescopes are able to resolve the central star.

My image of NGC 7662 was taken with a 132mm f/7 apo using an SBIG ST-2000XCM CCD camera. The exposure was 20 minutes. In the image, north is up and east to the left. The brightest star in the image, lying left of the nebula is SAO53026, a magnitude 8.21, yellow-white F star. The next brightest star, to the upper left of the nebula is SAO53017, a magnitude 8.81 red dwarf.  The red dwarf appears brighter than the F star because the CCD camera is more sensitive to red light.  The faintest stars in the image are magnitude 15.

The inset on the upper right of the image is a zoomed in view of the nebula from the original image. This view shows some of the lobe structure within the nebula. I was unable to resolve the central star with this small telescope.