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(IAAC) OBJ: m16, m17 (emission) INST: 18" f/4.2 Dob-newt Twilight



Observer:  Todd Gross
Your skill:  Intermediate - Many years
Date and UT of observation: 3/27/99 09:35 GMT
Location & latitude: 22 mi. West of Boston, Ma. 42.3N
Site classification: Suburban
Limiting magnitude (visual): approx. 4.7 zenith,about 4.1 vicinity objects
Seeing (1 to 10 - worst-best): 6+
Moon up (phase?): No
Weather: Clear, twilight just started
Instrument: 18" f/4.2 fl=1925mm Newt 
Magnifications: 82x
Filters used: OIII Lumicon filter
Object: M16 M17
Constellation: ser
Object data: Galaxies
Size(s):  M16-35'  M17-46', but only middle seen here
Position:18:20RA 13:47south, and 16:11south-M17
Magnitude: 6 (both)
Personal "rating" (at this aperture, and sky condition): B/B+(m16)/A-(m17)
It was risky, due to heavy light pollution and twilight already in place. 
However, the OIII filter gave me a fine view of M17's central area, and I
could
make out nebulosity in M16 amidst the cluster. 
M16 appears as a medium sized elongated, snaking, cluster of 
bright stars, fairly close together, but still somewhat "loose". 
Roughly the same brightness on most of them. This is on top of a nebulous
background that is very large, extending beyond the 8/10 of a degree 
field of view, even though it is listed as smaller. Did not make detail out
in the nebulosity.
In contrast.. M17 took on it's classic form as a swan swimming from right to 
left. A foreground star on the nose of the swan, and a nebulous "cap" right 
above the swan shape. Again, this was a horizontal bar of nebulosity, with one
on top on one end.. resembling a head, and thus creating what looks like a
duck
or  "swan".. with another little dash of nebulosity above that.. looking like 
a hovering cap. Remaining surrounding nebulosity seen in photos not detected 
in this sky condition... so what I saw was just a fraction of the listed
size..
it was perhaps 20 arc minutes long. 
I tried M16 w/o the filter, could not see the nebulosity, but the cluster 
was prettier that way. M17 I did not even attempt w/o the filter in this
sky condition.
thanks! 
-Todd
Boston Meteorologist Todd Gross
toddg@weatherman.com
http://www.weatherman.com
(617)725-0777
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