Located about 2.5 degrees east of bright star, Alpha Cassiopeiae, is emission nebula, NGC 281. This is a very large and faint nebula, with very low surface brightness. It was discovered in 1883, by E.E. Barnard.
This nebula is often called the “Pacman Nebula” due to its similarity to the video game character, however, an O-III filter is required to see this unique shape and feature. This object is in perfect position for both early to late fall observing.
What is an emission nebula? An emission nebula is an ionized-hydrogen region whose spectrum consists of emission lines by a glowing gas under low pressure. An emission nebula differs from a reflection nebula in that it produces it’s own light. A reflection nebula is a cloud of interstellar gas which is illuminated by a nearby star.
I found NGC 281 to be very challenging when using a 10-inch reflector from my moderately light polluted backyard, in the foothills of Western North Carolina. I was very surprised that it could be seen, however, very dimly, with an 8 x 50 finder. At 57x, this object appears mostly round with very little detail. When increasing the magnification to 104x, and adding an O-III filter, this nebula really came to life. The northern part is rounded, resembling that of a helmet. Just below the rounded area is an area, devoid of any nebulosity, and to the east is a section which curves toward the southeast. The nebula is much more concentrated and a bit brighter in the northeast. The southeastern curving tail is fairly difficult, even with the use of the O-lll filter, mostly due in-part to several unshielded streetlights being in relative close proximity.
In the central region is a faint triangle of four stars, however, I could only see three. This multiple star is Burnham 1, named after S.W. Burnham. This small group of of bluish-white stars really adds to the beauty of this object. The misty nebula, encapsulating the trio of stars creates a beautiful sight, but there’s even more to this object. IC 1590, a small and very faint open star cluster is also located within the nebula, but I was unable to see or recognize this cluster during any of my observations.
Sue French from New York, using a 10-inch reflector said “Nice large nebula, improved with a UHC filter, even better with an O-III. When using a 4.1-inch refractor, a faint nebula surrounding a pretty trio of stars.”
Jaakko Saloranta of Finland “bright enough to be spotted under less than good skies, using a 4.8-inch refractor with an O-lll filter.”
Gus Johnson of Maryland “found it easily with a 4 1/4-inch reflector. In the fall of 1968, using a 6-inch reflector at 148x, was able to see all four stars of Burnham 1.” Note: Gus was the founder of SN 1979C, and only the second amateur at that time to visually discover a supernova.)
Fred Rayworth of Nevada using a 16-inch reflector from Cathedral Gorge “a mostly round nebula at 102x, but when adding an O-III the “Pacman” shape was easy. Could see only three stars in Burnham 1.”
The following sketch was made by the writer, using a No. 2 pencil and a blank 5 x 8 note card. The colors were inverted using a scanner. The telescope used was a 10-inch f/4.5 reflector and with the employ of an O-III nebula filter.
The following image was made by James Dire, formerly of North Carolina, now residing in Hawaii. Dire used an Orion 190 mm Maksutov-Newtonian f/5.3 to make this beautiful image.
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