Object of the Week September 3, 2017 – IC 5217
Object of the Week September 3, 2017 – IC 5217
IC 5217, PK 100-5.1
Type: Planetary Nebula
Constellation: Lacerta
RA: 22h 23m 55.7s
DEC: +50° 58’ 00”
Magnitude: 11.3
Size: 7”
Magnitude (central star): 15.5
The Labor Day holiday this weekend in the United States serves as the demarcation between the Summer and Fall seasons. Although Fall doesn’t officially arrive here in the Northern Hemisphere until the Autumnal Equinox on September 22. Yet the last vestiges of Summer are upon us. The good news is that for some of us that means more observing – by taking advantage of longer nights, less humidity, better transparency, and fewer bugs, especially the annoying mosquitoes here in the Midwest. For me the true harbinger of the approaching change in seasons is the sight of Orion rising on its side from the Southeastern skies shortly before the sunrise.
This week’s Object of the Week serves as a challenging warm-up for any observer and instrument that might have sat idle throughout the dog days of Summer. Our OOTW target is IC 5217, a planetary nebula in the constellation of Lacerta. Philip Harrington, in Cosmic Challenge: The Ultimate Observing List for Amateurs, sets the stage by aptly describing IC 5217 as the “taxing planetary in an equally taxing constellation.” Don’t be embarrassed if you are thinking…so exactly where is Lacerta? The constellation lies between Andromeda and Cygnus. The brightest stars in Lacerta are only of fourth magnitude and none of them have proper names. There are no myths associated with the constellation. There are no Messier objects in Lacerta. By the way its name means “the lizard” in Latin. The few deep sky objects in the constellation are primarily small open clusters with two notable exceptions: an active galactic nucleus, BL Lacertae, and our OOTW this week, IC 5217.
IC 5217 was discovered in 1904 by Williamina Fleming of Harvard College Observatory. It was nearly 100 years later before planetary’s bipolar structure was confirmed: it has a very bright equatorial ring and open bipolar lobes.
Despite Harrington’s dire warning, tracking down this planetary nebula can be easier than one might expect due to its high surface brightness and its excellent response to an O-III filter. IC 5217 is located pretty much on a straight line mid-way between the stars 4 and Beta Lacertae. At low power, it has a stellar appearance, like any other bright 11th magnitude star, however a slight green tinge might be detectable. Moderate power reveals a small blurry disk, which is even and round in appearance, and the green cast may seem to increase. Apply an O-III filter and it becomes apparent that this is not a star.
Not everyone sees the planetary as green. Steve Gottlieb, Deep Sky Forum/Object of the Week contributor and Sky & Telescope Contributing Editor, logged an observation in July 2008 with an 18” scope noting the color at 174x as pale blue and at 435x the disc as blue.
IC 5217 requires large apertures and high power, as well as steady seeing, to pull out any detail from the planetary nebula. Greg Crinklaw, author of SkyTools 3, logged this observation with an 18” scope, “The best view came at 860x, where it took on the appearance of a little saturn nebula (at least as seen in some photographs). It appeared distinctly oval and left the impression of little "handles" sticking out of either end. This planetary blinks dramatically with any eye movement at this magnification.” Greg also states to be sure to note (at low power) the nearby star chain slightly northwest of the planetary.
The central star at a magnitude of 15.5 is difficult, if not impossible to observe visually, due to the high surface brightness of the planetary nebula overwhelming the faint central star.
• What do you see at low and medium powers? With and without an O-III filter?
• What color(s) do you see? With and without an O-III filter?
• What detail do you see at high powers? With and without an O-III filter?
• Are you able to detect the central star? With what aperture and power?
Give it a go and let us know.
