M 20 (LBN 27, NGC 6514, Lund 803) aka "The Trifid"
Bright Nebula / Reflection Nebula / Open Cluster in Sagittarius
Located at: RA 18 hours 02 minutes 25 seconds, Dec -22 degrees 59 minutes 00 seconds
Size: 17' x 12' (30') Magnitude: 9.0 Class: Emission + Reflection + Dark Lanes
North is up
West to the right
14.5" f5 Newtonian reflector
ST-8XME, self-guided, binned 1x1, temp -20c, camera control MaxIm DL 4.56
Lumicon Red filter, 590 minutes (59 x 10 minute subs), 08/10/11/12/2013; seeing 3.9-4.7 FWHM per CCDStack
CCDStack 2.74.4938.18664, Photoshop CS5.1
Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)
|Notes:||M 20 is a complex object; with a blue reflection component to the north
(around the bright star immediately above the three dark lanes), and the
southern bright nebula split by dark
lanes (B 85).
From "Star Clusters", by Brent Archinal and Steven Hynes, in the 'Notes' section, they state, in part: "The NGC and M designations apply to both the star cluster and nebulae. Messier only notes the cluster under his description of M 20, but adds under his description of M 21 that both objects were involved in nebulosity." The size of the open cluster (Lund 803) is 30 arc minutes.
From the NGC / IC Project:Contemporary Visual Observation(s) for NGC 6514
NGC 6514 = M20 = Trifid Nebula = B85 = LBN 27 = Cr 360 18 02 42 -22 58.3 V = 6.3; Size 29x27 13.1": bright, fairly large, contains three inky black dark lanes (B85) with sharp edges. Structure is visible along the dark lanes and in the center. The prominent central star is a quadruple (4th star difficult) consisting of a mag 7.6/10.4 pair at 6" and a mag 8.7/10.5 pair at 2.3". The NW lane is wider and fainter than the other two lanes. A round, bluish reflection nebula is separated, but very close north. The view improves using a UHC filter. 8": the famous rift structure is fairly prominent with a triple star at the center. The NW rift is more subdued. An easily visible reflection nebula is close N. - by Steve GottliebHistorical Research Notes / Correction for NGC 6514
NGC 6533 = M8 = H V 13. WH's position for this, reduced from the offsets published in the Scientific Papers is in a pretty empty patch of sky roughly 30 arcmin south of M8. He does give a pretty good description in his 1786 first catalogue, however. He observed it only one night, 12 July 1784: "Extensive milky nebulosity divided into 2 parts; the most northern above [larger than] 15 arcmin, the most southern followed by stars." What struck me about this was its uncanny similarity to his description of M8 given in his 1785 paper (which I unfortunately do not have a copy of), quoted by Kenneth Glyn Jones in his fine book on the Messier objects: "An extensive milky Nebulosity divided into two parts; the north being the strongest. Its extent exceeds 15 arcmin; the southern part is followed by a parcel of stars which I suppose to be the 8th of the Connaissance des Temps [i.e. M8]." WH's 1786 description reads like a simple condensation of his 1785 description. Is it therefore possible that H V 13 = N6533 is M8? WH's position doesn't encourage that interpretation. Both JH (in GC) and Dreyer (in WH's Scientific Papers which he edited in 1912) have notes about WH's problems determining the position -- as I've noted, that position is over 30 arcmin south-southeast of M8 in a barren patch of sky. But if WH was indeed looking at M8, is there any way that his offsets (4m 54s following, 38':: south of 5 Sagittarii) can be made to fit? Well, once I tracked down 5 Sgr (it is SAO 186074, not labeled as "5 Sgr" in Sky Catalogue 2000.0), it was clear that the NGC position was properly reduced (once the earlier bugs found by JH had been cleaned up. He says in GC that the offset as originally published in PT for 1786 -- 39' north -- is wrong.). Did WH observe any other nebulae that night? In particular, did he use that same comparison star? The answers are "Yes" to both questions. H V 10, H V 11, and H V 12, all = NGC 6514 = M20 = the well-known "Trifid Nebula" have a single position referred to that same star on that same night. When we reduce that position, we find that it is about 30 arcmin south-southeast of M20 in a barren patch of sky .... Yet there is no doubt that these three nebulae constitute M20 (along with IV 41); both JH and Dreyer accept that in GC and NGC. So what's going on? The short of it: WH may have misidentified his comparison star (but see also N6698, found the same night, referred to a different star). He probably used 4 Sgr = SAO 186061, rather than 5 Sgr as is printed. Once that correction is made, it's clear that NGC 6533 is, in fact, M8. WH's resultant position is about a minute of time following the brightest part of the nebula (N6523), but is more in line with the center of the entire complex as we see it on photographs. However, as Steve and I have noted before, WH's positions from these early runs of 1783 and 1784 have generally larger errors than his later positions -- he was still perfecting his observing techniques. The mystery here is this: if JH and Dreyer knew that H V 10-12 referred to the Trifid, why then did they not make the connection -- through the comparison star in common -- to the Lagoon as well? I don't see an answer to this in any of the papers I have in my collection. However, if there is any information in WH's 1785 paper that might shed some light on this, we should look at it again. M8 also encompasses several other NGC and IC objects: NGC 6523, NGC 6526, NGC 6530, IC 1271, and IC 4678, all of which see for more discussion. - Dr. Harold G. Corwin, Jr. ================================================================= NGC 6514. See NGC 6533. - Dr. Harold G. Corwin, Jr.
This description for B 85 from the on-line Edward Emerson Barnard "A Photographic Atlas of Selected Regions of The Milky Way":