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Designations: M101, NGC5457, Pinwheel Galaxy
Visual
Magnitude: 7.9
Size: 28.8 min X 26.9 min
Distance: 17.5 light
years
Discoverer: Pierre Mechain,
1781
Visual Description: M101's numerous,
far flung arms and distinct asymmetry make it readily identifiable in
photographs. Visually, its pale 9th-magnitude glow is diffuse and difficult to
make out, yet it has much to offer if you are patient. It is easy to locate,
because you can star-hop to it from the famous visual double star Alcor and
Mizar in the handle of the Big Dipper. Southeast of this pair is a path of four
5th-magnitude stars (81, 83, 84 and 86 Ursae Majoris) that leads in the
direction of M101, which lies 1 1/2 degrees east-northeast of 86 Ursae at the
end of the trail. The galaxy is visible in binoculars, so try them first before
taking to the telescope. Telescopically, at 23 X the galaxy's core is compact
but slightly elliptical. Knots in phantom spirals emerge from the galactic
mists, but moderate power is much more effective in coaxing them out. Low power
is best saved for determining the full extent of the far-flung arms. High power
on the other hand, is your best bet for examining the inner region which shows a
sharp nucleus inside a pentagon-shaped core. Only two arms are very definite;
beyond that everything fades out of view. You may have to alternate between
moderate and low power to preserve your sanity as you try to keep track of their
directions.
Seeing Conditions:
Not Recorded
Telescope: TMB
152 f8 APO refractor
Focal Length:
1200 mm
Mount: Takahashi
NJP 160
Camera: SBIG
ST10XME
Exposure:
15 12-minute exposures for luminance and 4 15-minute exposures for each
color (R,G,B). Total exposure time is 6-hours.
Other:
SBIG
ST402ME
Autoguider
Image Processing: Images were combined in CCDStack and processed in Photoshop CS2
The Visual description of the M101 Galaxy was writen by Steven James O'Meara in the book "The Messier Objects" by Stephen James O'Meara. Page. 265. ISBN number 0-521-55332-6.
Copyright(c) 2007 Doug Sanqunetti. All rights reserved
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