Object of the Week February 1, 2015 IC 3568, The Lemon Slice Nebula

Object of the Week February 1, 2015 IC 3568, The Lemon Slice Nebula -or- the Baby Eskimo Nebula
IC 3568, PK 123+34.01, UGC 7731, PN G123.6+34.5, ARO 56

Planetary Nebula - Camelopardalis

R.A.: 12h33m06.8s
Dec.: +82°33'50" (2000)

Size: 18"

Mag: 11.1 V
Mag: 11.4 B

IC 3568 is a tiny but bright planetary nebula only about 8 degrees from Polaris, so it is available most of the year to those of us in the mid latitudes of the northern hemisphere. Apparently Jay McNeil gave it the 'Baby Eskimo' nickname, but a look at the Hubble photo clearly illustrates why most folks now use its more familiar handle, the 'Lemon Slice' nebula. As per Balick et al, 'morphologically it is one of the simplest planetary nebulae in the sky.' http://adsabs.harvard.edu/full/1987AJ.....94..948B

Attachment 1516

Interestingly, Megastar shows a galaxy, UGC 7731, as being co-located at this position, and Simbad additionally shows this PN to have a LEDA designation, so at some point in the past it must have been assumed to be a galaxy. The NGC/IC Project does not have data on this fellow.

My own best observation of this guy was made during the Oregon Star Party in 2001, where I enjoyed the finest star party skies ever! SkyTools indicates a diameter of 18 arc-seconds, but a viewed under great skies with a 20" f5 Obsession it didn't seem to be that large, it appeared to be perhaps 12 or so arc-seconds across. The central star, listed at mag 13.4, was glimpsed only at fairly high power, about 400X or so, largely because the high surface brightness of this planetary tends to mask it. The disk itself showed only a slight bit of color, essentially gray but maybe with a bluish or greenish tinge. Whatever the tint, it was very subtle. I observed no structure within the nebula whatsoever, the perfectly round disk simply faded away to a fuzzy and vague outer edge. An OIII filter increased the contrast but did not help to reveal any structure.

Attachment 1515

There is a mag 14 star in the field, about 12 arc-seconds mostly west and just a little south (PA 263). Together they almost look like a double star with one member being quite fuzzy.

As always, give it a go and let us know!

The Balick paper that Paul links has another quote -- "If IC 3568 did not exist, it might have been created by theoreticians" (referring to its circular symmetry).

That led to a third nickname -- the "Theoretician's Planetary"

Also saw this PN in Camelopardalis in 2006 with a 20"f5: "Bright disk with a little faintness around the edges. Filter did not enhance it, white color."

Al

My last observation is from 2009 with my 28 inch:

"Two concentric rings with the center being irregularly dark but with a fairly distinct boundary with the fainter outer ring. The slight blue tint (seen) at low power disappears at 253x and up. The sketch was drawn using 654x and no filters. 21.15 SQM."

Attachment 1517 Attachment 1518

I'll add that I'd observed IC 3568 a few night before but the seeing wasn't nearly as steady as on this particular night (January 20, 2009) so I didn't see nearly as much.

Here are my sketched notes under good but not perfect transparency and seeing

27", 837x, no filter, Seeing III, NELM 6m5+
Attachment 1519

I like this one. Observing from Cherry Springs with my 16" f/4.5, I recorded: "“Theoretician’s Planetary”. Bluish. Faint star 1 diameter to the W. Center brighter, nonstellar, edge diffuse." Mere 225x was used, really a passing observation. Some great ones in this thread.

Here's another observation with my 18-inch:

18" (11/7/07): at 450x unfiltered a very bright, high surface brightness disc 6"-8" in diameter is surrounded by a much fainter 15"-18" halo. With direct vision, the difficult mag 13.5 central star is sometimes visible within the very high surface brightness glow. The outer envelope is round, though with a uneven or fuzzy edge. A mag 13.5-14 star is close off the west edge just 15" from the center and a mag 11.5 star lies 1.6' SSW.

I just noticed that I observed this object in April 2006 with my 6" telescope. My notes roughly translate as written below. The star I refer to probably is m=11.4 TYC 04633-1711 1.

This planetary nebula already is visible at 32x together with a star of about the same brightness. At 170x it is clearly visible that the nebula isn't a point source, but a small ball. The nebula responds very well to blinking with an OIII filter. No other details are visible except for a fuzzy ball with no central star.


Clear skies,

Wouter van Reeven