[AZ-Observing] Re: Sunday not too hot either....

Thad,

Here's the scoop on NGC 6882/6885.  These are Dr. Harold Corwin's notes on
the object(s).

==========================================================
NGC 6882 is probably a duplicate observation of NGC 6885.  Both clusters
were
found by WH on subsequent nights (9 and 10 Sept 1784; N6882 is from 10
Sept),
were refered to the same star, and have almost identical descriptions ("A
cluster of coarsely scattered stars."  For NGC 6885, he adds, "... not
rich").

There is nothing striking near the position of N6882, but that for N6885 is
in
the middle of a large scattered cluster also observed by JH.  Over the
years,
there has been considerable speculation about what WH saw.  Some observers
have made the clusters identical, while others (notably Reinmuth) have
pointed
at the wide group of three bright (m = 6) stars about 20 arcmin north of
N6885.  Brent Archinal believes that the clump of nine stars at 20 09 51,
+26 35.1, including HD xxxxxx (the southernmost of Reinmuth's three stars),
is
N6882.  This is unlikely as the clump is only two arcmin across.  Had WH
seen
this, he would most likely have put it into his 7th class; it certainly is
not
"coarsely scattered."

Neither of these matches WH's description, so I'm more inclined to the
identity of the two NGC objects.  This would imply an error of 15 arcmin in
WH's declination; the RA's are 12 seconds different, but both are still well
within the central part of the cluster (which is over 20 arcmin across).

Adding to my conviction that N6882 = N6885 is the fact that, of the seven
objects found by WH on 10 Sept 1784, four have significant offsets in WH's
positions (the three besides N6882 are:  N6800, -1 minute off in RA; N7720,
+40 seconds off in RA; and N7741, +4 arcmin off in Dec).  WH was clearly not
up to snuff that night, and the +15 arcmin error in the declination of N6882
fits right in with the other problems.
=======================================================

Hope this helps,

/Bob


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