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(IAAC) Obj: M 108 - Inst: 8" f/10 SCT, 8x50



Observer: Lew Gramer
Your skills: Intermediate
Date and UT of Observation: 1997-11-29/30, 03:00 UT
Location: Miles Standish State Forest, Carver, MA, USA (41N)
Site classification: rural
Limiting magnitude: 6.6 (zenith), 6.2 (in NE)
Seeing: 2 of 10 - excellent
Moon up: no
Instrument: 8" f/10 Schmidt-Cassegrain on fork equatorial, 8x50mm finder
Magnification: 80x, 170x
Filters used: None, UHC
Object: M108
Category: Spiral galaxy [SB(s)cdsp]
Constellation: UMa
Data: mag 10.0  size 8.7'x2.2'
RA/DE: 11h12m  +55o40m
Description:
Readily swept up from bright white "bowl star" Merak (beta UMa),
by shifting one eyepiece field S then heading E 1.5o to the end
of a trail of mag 8-10 stars. Viewing this "poor sister" of the
Messier galaxies at 170x strikingly reminiscent of seeing M82
at a lower power: a disturbed inner core raying out in at least
three directions from a relatively smooth, elongated outer core,
all set amid a still more elongated but otherwise featurelessly
faint halo. No central nucleus was noted at either power on M108
tonight, although stellarings were apparent within the core and
the W extension of the halo. Using UHC tonight did NOT bring any
of these stellarings out more prominently, actually losing the
star at center (along with much of the light in the outer core,
and all the halo). This surprised me, as I had expected in spite
of the aperture to see some HII regions with the UHC tonight...
--
[By contrast, with a larger aperture the difference between these
two stellar islands can be very striking: M82 shows streamers and
fans of light raying out from a bifurcated central core. Meanwhile
M108 shows both its core and halo irregularly disturbed over much
of their length, and is barely recognizable as a spindle at all.
Has anyone else noted the similarities between these two in 8"?]