Designations: M109, NGC 3992
Object Type:Barred Spiral
Constellation: Ursa Major
RA: 11 hrs 57.6 min
Dec: +53 deg 23 min
Visual
Magnitude: 9.8 SB:
13.5
Size: 7.6 min X 4.7 min
Distance: 55 million light
years
Discoverer: Pierre Mechain 1781-1782
Visual Description: M109 is a typical
barred spiral galaxy; in fact, about one-third of all known spirals are of this
nature, characterized by a prominent central bar of stars off of which flow more
delicate spiral arms. Glowing at 10th magnitude, it can be seen in 7X35
binoculars 1 degree southeast of the 2.4 magnitude star Phecda (Gamma Ursae
Majoris) in the bottom of the Big Dipper's bowl. Whenever I sweep toward M109
and its oval shape enter the field, I get a tingle as if I have encountered a
comet, as Mechain must have when he first spotted the object. But, because this
glow is so close to 2nd-magnitude phecda, I wonder for a fleeting moment whether
I am just seeing a reflection of that star. A good tap on the telescope assures
me that I am not. At low power the galaxy displays a well-defined core and a
halo muddled with irregularities. Medium power proves it to be a more satisfying
barred spiral than either M91 in Coma Berenices or M95 in Leo. the central bar
of M109 appears prominent, and the nebulous arcs and hints of spiral arms that
emanate from it do not require a strong effort. It is noteworthy, however that
neigther Jones nor Clark could detect the bar in an 8-inch telescope; this might
say something about the galaxy's appearance in less-than-pristine skies.
Seeing
Conditions: Steady Skies but average
transparancy ~60% humidity and very cold. The image was degraded by
frost!!
Telescope: Meade 10" LX200 Optical Tube
Assembly
Focal
Length: 2500 mm
Mount: Takahashi NJP 160
Camera:
Starlight XPress
MX916
Exposure:
Multiple 1200 second
exposures stacked (added)
Other: S.T.A.R 2000 Autoguider
Image Processing: 5 20-minute exposures stacked (added). The dimmest parts of the image were blurred using a gausian blur filter. The brighter areas were sharpened using the unsharp mask filter.
The Visual description of the M109 Galaxy was writen by Steven James O'Meara in the book "The Messier Objects" by Stephen James O'Meara. Page. 281. ISBN number 0-521-55332-6.
Copyright(c) 2007 Doug Sanqunetti. All rights reserved
Astro
Images