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109, NGC 3992, Spiral Galaxy
M109, NGC 3992, in Ursa Major, is approximately 46 million ly distant. Its light
is equivalent to about 19 billion suns but because of its distance, it is quite
dim and a very long exposure — over 6 hours total — was needed. Its size —
about 100,000 ly — is in the same range as our Milky Way galaxy. The shape is
that of a barred spiral galaxy, so-called because of the distinct bar across the
diameter from the nucleus to the beginning of the spiral arms. it was originally
discovered by Mechain around 1781-2. The apparent size is 7.6 x 4.3 arcmin,
which puts it in the range of the 2858 mm focal length f/9 Ritchey-Chretien
telescope used for the image. North is up in this image.
scope at f/9 with ST-10XME CCD camera at -15 °C
A-P 1200 GTO mount.
Guided with internal guide chip. SBIG CFW-8 filter wheel.
18 - 5 min exposures
R, G, B at 2x2 binning and 22 - 5 min exposures through the clear
filter for the
luminance image at 1x1
binning. Total 380 minutes.
Raw frames calibrated in MaxIm 3.09. Master
L, R, G, and B frames were then created in MaxIm.
gradient was removed from the red master by means of Wodaski's
DDP processing was carried out on each of the master frames. The RGB color
combine was then carried out in
MaxIm with a weighting of 1.2, 1.0, and 1.2, for RGB, respectively.
luminance image was then registered with the RGB image in RegiStar. The
were imported into
Photoshop and combined with the L image as Luminosity at 100%
The RGB and luminosity layers were
then separately adjusted with Levels and Curves before flattening
converting to a jpg file.
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