NGC 6888

NGC 6888 = Crescent Nebula = LBN 203 = Sh 2-105
20 12 06.5 +38 21 17
Size 20x10

18" (8/23/03): Using a 6-inch off-axis mask with a 31 Nagler (73x) and an OIII 
filter, a faint curving arc is visible which begins SW of the mag 7.2 star on 
the north edge and curves around to the mag 8.2 star on the NE side, extending 
nearly 90? of along the annulus of the Crescent Nebula.  No other nebulosity was 
visible.

17.5" (6/29/00): Stunning view at 100x (20mm Nagler) using an OIII filter.  The 
outline appears as a huge, irregular cosmic egg, ~18'x11', floating in a very 
rich Cygnus star field.  The complete annulus is easily visible.  The brightest 
section is along the north side and passes through a mag 7.2 star at the north 
edge.  This piece displays much structure with several knots and wispy tendrils.  
An isolated bright knot is within the weakly glowing interior which has an 
irregular surface brightness and is on a line with the mag 7.2 star and the mag 
7.4 central star.  There are interior wispy striations which appear to radiate 
from the central star towards the NW rim at the end of the bright arc.  The rim 
is widest on the SW end with more nebulosity filling in towards the center.  The 
fine texture and structure of the nebulosity creates a 3-dimensional feel and an 
"electric" effect.

17.5": the "Crescent Nebula" is one of my favorite large nebulosities at 100x 
with a OIII filter (excellent contrast gain).  Appears as a bright, 16'x11' oval 
or egg-shaped annulus elongated SW-NE.  The rim is virtually complete except for 
a small piece of the east side and exhibits a great deal of turbulent, wispy 
structure.  Brightest just SW of mag 7.2 SAO 69597 (unequal pair 7.2/10.5 at 
14") which is embedded in the rim at the north end.  The nebula also passes 
through mag 8.2 SAO 69611 on the NE side.  Just north of center in the interior 
is the mag 7.4 Wolf-Rayet star HD 192163 = WR 136, whose strong stellar wind 
created this shocked ring-type nebula.  This is beautiful nebulosity set in a 
very rich milky way field.

13": bright, large, oval shell, nearly complete loop visible with UHC, striking 
unusual appearance!

8": faint, elongated arc of nebulosity connecting two mag 7.5/8.5 stars and 
extending SW of the brighter star.  Set in a very rich star field.  Only the 
brightest portion at the north end of the nebula is visible.

- by Steve Gottlieb

NGC 6888 is a large oval-shaped HII region (Sharpless 105), brightest along 
its northeastern side.  WH's place is close to the knots and streamers on that
side of the nebula, and it is clear from his description that that is the part 
he saw.  

Bigourdan puts the position closer to the center of the oval.  He descriptions
of the field on two nights (he claims to have seen the nebula on only one of
them) makes it clear that he did not see WH's object, just two stars near the 
revised place given in the IC2 notes.  It looks like purest coincidence that
this is near the center of the HII region. - Dr. Harold G. Corwin, Jr.

As with all corrections to the NGC and IC Catalogues, there is a certain margin
for error, even though the evidence supporting the correction may be strong and
compelling. It is with this in mind that we ask the user to use this information
as 'Most Probable', but never to assume the correction is 'Absolute'.  All
published corrections are based on an exhaustive 'paper chase' of the historical
record back to the original discoverer's published notes/papers, and are
therefore based upon the historical accuracy (or inaccuracy) of those particular
notes/papers. In short, Caveat Emptor! - Robert E. Erdmann, Jr.