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RA: 18h 12m 6.365s
Dec: +06° 51′ 13.01″
Ch: MSA:1272, U2:204, SA:15
Type: planetary nebula
Mag: B=9.3, V=8.4
Discovered in 1825 by Wilhelm Struve, he called it one of the "most curious objects in the heavens."
Burnham, S. W. () "Measures of planetary nebulae with the 36-inch equatorial of the Lick Observatory", Pub. Lick Obs., vol 2, p159-167. This is one of the brightest of the planetary nebulae. It is sometimes spoken of as[sigma]6, which is an unfortuante as well as an imporper method of refering to the list of nebulae observed by Struve, since the symbol [sigma] preceding a numeral has been universally used to designate double stars ..."
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part II. M.N.R.A.S., 35(8), 280.
Terzian Y (1980) Q.J. R.astr.Soc vol 21, p82-92 [09.16.1] notes that the central star of this planetary is a spectroscopic binary.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.5 mag planetary nebula.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 15" diameter; shows clean, greenish disc at 300x; 11M star 5' due E."
Houston notes that this is an easy planetary nebula in Ophiuchus, one of many that stud the summer Milky Way. He calls it "a beautiful little gem about 12 arcseconds long and half as wide. Its total light is about equivalent to a 9th mag star, while its surface brightness is a hundred times that of the Ring nebula in Lyra. The central star is not difficult, being of 11th magnitude visually. Houston notes that even though the planetary is bright, it is only 16 arcseconds across, and a power of 100x is best for picking it out from the many field stars. He adds, however, that in 15x65 binoculars it appears as a star, if one knows just where to look.
In 1978, Houston wrote: "I could distinguish the disk of this 7" diameter object with a 4-inch RFT at 20 power. . In a 6-inch at 100x it appeared as a pretty gem, slightly oval with a definite green colour. It is interesting to note that the older observers in our group all considered NGC 6572 to be green, while the younger members called it vivid blue."
Subj: Re: Interesting Popular names for Deep Sky Objects...
Date: Sun, 23 Oct 1994 08:57:36 -0500 (CDT)
One of my favorites is the "Lime Jello" nebula in Ophiuchus.
It is also called (rather mundanely) NGC6572.
It is a 9.5 mag planetary nebula that is a brilliant GREEN color to
the unfiltered eye.
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 6572 (PK 043+37.1; PN G043.1+37.7; ARO 5, VV 82) Category: planetary nebula Constellation: HER Object data: Vmag=8.8; Bmag=9.3; 20"x13"; type II+IIIb; central star of Bmag=12.5; discovered by Struve in 1827; ELCAT: [OIII, 496+501nm] = 15 x [Hbeta, 486nm]. RA/DE: 16h44.49m, +23°48.0' (2000.0) Date and UT of observation: 09-10 July 1989, ... Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.0 Transparency (1 to 5 - best to worst): 1 Seeing (1 to 5 - best to worst): ? Moon up (phase?): no Instrument: Japanese Newtonian 4.25"/114mm f/7.8 Magnification: +100x Filters used: -
Description: seen and located only from 100x and so on; at 100x, just nebulous; at 150 & 180x, nebulous star.
Observer: Yann POTHIER (France) Your skill: advanced (many years) Object: NGC 6572 (PK 043+37.1; PN G043.1+37.7; ARO 5, VV 82) Category: planetary nebula Constellation: HER Object data: Vmag=8.8; Bmag=9.3; 20"x13"; type II+IIIb; central star of Bmag=12.5; discovered by Struve in 1827; ELCAT: [OIII, 496+501nm] = 15 x [Hbeta, 486nm]. RA/DE: 16h44.49m, +23°48.0' (2000.0) Date and UT of observation: 31 July 1989, morning Location & latitude: La Clapiere Obs. (France, latN44 40 00, longE06 27 36) Site classification: rural, alt.1650m (5500ft) Limiting magnitude (visual in UMi): 6.0 Transparency (1 to 5 - best to worst): 2 Seeing (1 to 5 - best to worst): 3 Moon up (phase?): no Instrument: Meade SCT 8"/203mm f/10 Magnification: 87-312x Filters used: -
Description: at 145x, found at this power; forms a triangle with 2 stars; already nebulous at 100x (slightly); at 225x, compact nebulosity; at 310x, bluish, large and homogeneous.
Observer: Todd Gross
Your skill: Intermediate - Many years
Date and UT of observation: 3/09/99 09:00 GMT
Location & latitude: 22 mi. West of Boston, Ma. 42.3N
Site classification: Suburban
Limiting magnitude (visual): approx. 4.7 zenith
Seeing (1 to 10 - worst-best): about 3
Moon up (phase?): Yes, last 1/4 (just over)
Weather: Crystal Clear
Instrument: C9.25" SCT f/10 f.l.2350
Magnifications: 123 & 235x
Filters used: none
Object: NGC6572 & NGC6210
Constellations: Ophiuchus and Hercules
Object data: Planetaries
Size(s): 13" 6572, 17" 6210
Magnitudes: Both near 9
Personal "rating" (at this aperture, and sky condition): B/B-
These little planetaries are striking for their color. I first viewed NGC6572 through this 9.25" SCT and at lower magnification, it looked like a fuzzy blue star. At 235x, a very bright, striking blue (cyan) fuzzball brightest in the center. I then moved to 6210 and made a comparison. NGC6210 is almost identical. It is slightly larger, a bit more diffuse (slightly) and a bit less striking in surface brightness and color. However, the two could be twins! As you can tell I liked 6572 a bit more as one of the most colorful objects I have seen at this aperture.
Boston Meteorologist Todd Gross
Steve Coe, using a 13" f/5.6, notes: "Bright, large, elongated 1.5 X 1 in PA 135 using 220X. The central star is held steady in good seeing conditions. Other times the center will just brighten up somewhat. The noteworthy aspect of this gem is its' color. In every scope I have ever owned, from an 8" to an 18" this is the greenest nebula I have ever seen! This guy is as green as an Irishman's coat on St. Patrick's day. Alright, alright, it is as green as lime Jello. 13" Table Mesa 5/10 trans, 6/10 seeing- 100X--immediately obvious, Beautiful Easter Egg afloat in the Milky Way, bright and small. 220X--bright, small, little elongated PA 75, averted vision shows a dim outer haze, there is a bright center that is about 4 X 5 arcsec in size, the outer hazy section is twice that size. The central star is held steady. 330X-- outer haze in obvious. Central star held steady and looks blue-white. The nebula is still a beautiful blue-green color. UHC doesn't help."
Observing site: Little Tycho Observatory
[18h 12m 6s, 6° 51m 0s] Like a star that never focuses well. A pale blue or green planetary that looks brighter than the 8.7 Mv star 3 arc minutes west of it. It looks smaller than the size Burnham gives it, 15 x 12".
The Messier objects
The Bennett objects
The Caldwell list
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