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(IAAC) Obj: M4, ngc6144, Cr302, B42, VdB302, Sh2-9 - Inst: 5" f/5 refractor



Observer: Lew Gramer
Your skills: Intermediate
Date and UT of Observation: 1997-07-4/5, 04:40 UT
Location: Savoy, MA, USA (42N, elev 700m)
Site classification: rural
Limiting magnitude: 7.2 (zenith)
Seeing: 5 of 10 - mediocre
Moon up: no
Instrument: 5" f/5 Jaegers refractor on altaz mount
Magnification: 18x (3.7o field), 25x (2o field)
Filters used: None
Object: M4, ngc6144, Cr302, B42 (VdB302 and Sh2-9 NOT seen)
Category: Globulars (amid large Open Cluster and Dark Nebula)
Constellation: Sco
Data: mags 5.4, 9.1, 1.0   size 35', 9.3', 8o
RA/DE: 16h25m  -26o
Description:
M4 was a magnificent sight in a rich-field scope under these
tar-pool black skies! Visibly elongated N-S and 20' long by
about 15' wide, M4 was relatively homogeneous in brightness
across its hazy face, and stunning even at this low power.
Unlike in nastier urban skies, the globular shows definite
signs of resolution, especially on it's N and S extensions,
and is far more intriguing and complex than the mere "spot"
which I'm used to seeing in Boston! n6144 can be seen in
the same spectacular, star-studded 2o eyepiece field, as a
fairly faint "dot", looking in fact very much like M4 does
under worse skies! With 18x, the addition of mag. 1 alpha
(Antares), mag. 3 sigma Sco, and the many field stars near
the center of huge open cluster "Collinder 302" (which takes
up much of the constellation Sco!), make this a field of view
nearly unsurpassed as far as RFTs on dark Summer nights go!
One interesting thing I noted at the time was that many of
the field stars seemed concentrated toward the M4 (S) end
of the 18x Panoptic field. Later chart examination shows in
fact a large dark nebula (Barnard 42) interposed onto this
area from Ophiuchus to the NE. Finally and not surprisingly,
no hint of the reflection nebulosities Van der Bergh 107 or
Sharpless 2-9 (around alpha Sco and sigma Sco respectively)
could be seen at either power, using any vision trick!