M51 and NGC5195

Owl Nebula
All Images
Copyright Steve Cannistra

Magnitude:  8.4
Size: about 11' x 7'
Distance: 37 million light years
RA (J2000): 13h 29m 54s
Dec (J2000): 47 degrees 12' 17"
Position Angle (Pinpoint):  +87 degrees 26'

Note:  This is the second light image for my VC200L scope (FL 1800mm, f9).  The FWHM in the 16 best subs was in the range of 3", and the star shapes are not yet perfect, indicating the need for a few more tweaks of collimation when the weather is warmer.   I'm not happy with it and feel that I can get better resolution on a night of good seeing and after perfect collimation.  I also need to get a better feel for the use of decon, and how much is too much, etc.  Finally, the image does not have enough depth in my view- lots of fainter stars are just at or below the level of sensitivity of my system.  This can be corrected by longer cumulative exposure, but I also intend to purchase a non-NIR blocked clear filter (instead of the NIR blocked luminance filter that I currently use) to catch as many photons as possible at f9.

The famous face-on spiral galaxy M51 (NGC 5194) is located in the constellation Canes Venatici (Hunting Dogs).   
It was originally discovered by Charles Messier in 1773, although its true spiral structure was first realized by Lord Rosse in 1845.  The galaxy has a characteristic shape, in the form of an inverted question mark, due to its association with another galaxy located well behind M51 in the above photograph, known as NGC 5195.  Note that this smaller galaxy is seen edge on and is partly obscured by a long, thin, prominent dust lane extending from M51.   Interaction between M51 and NGC5195 is thought to trigger new star formation in M51 itself, as represented by clusters of young, blue stars within the spiral arms.  M51 is a good target for visual observation through small aperture telescopes in dark skies, although it can be a challenging to discern its spiral structure in more light polluted skies.  More information about M51 may be found here.

Photographic Details:
Date:  March 30, 2008
Scope:  Vixen VC200L at f9 on the Takahashi NJP Mount.
Autoguider:  SBIG ST-402 with Sky90 at f4.5.
Camera:  Apogee U32 -20C.

Astronomik Luminance filter.
Exposures:  16 x 10' Total exposure 2.7 hours.
Conditions:  Temperature was approximately 35 degrees F; a little breezy.
Post-processing:  Calibrated, aligned, and Sigma Clip combined in Maxim, followed by deconvolution using Bob Vanderbei's Fat Tail Deconvolution script.  DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).

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