Messier 101 (Pinwheel Galaxy)

All Images Copyright Steve Cannistra

Please click here for a medium sized image (65%).
Please click here for the full scale image (100%).
Please click here for the color version of this image.

Magnitude:  Approximately 8.5
FOV: Approximately 19' x 28'
Distance: 27 million light years
RA (J2000): 14h 3m 10s
Dec (J2000): 54 degrees 21' 45"
Position Angle (Pinpoint):  plus 24 degrees

M101 is a large, beautiful spiral galaxy in Ursa Major.   The above image is a work in progress- it is not "perfect" yet and will be followed by a color version as soon as possible, but we are having a very rainy springtime.  This is a fairly deep, 4.3 hour exposure taken under moonless skies with the U32 and VC200L.  I am pleased with the detail revealed in this image after Lucy-Richardson deconvolution (resampled x 2, AIP4WIN, LR in Fast mode, PSF using about 20 stars, 20 iterations, relaxation parameter at 0.5, process high frequency components only, resample x 0.5).  I have tried a variety of deconvolution algorithms at this point and have settled on AIP4WIN's, since I feel that it gives the best results.   Check out the full scale image to see the detail present in this FOV, captured at a focal length of 1800 mm and aperture of only 8".   I am very pleased with this image since it shows that my collimation is excellent, and also shows that this very lightweight scope and camera combination has the potential that I had hoped for.  For visual observation, M101 is best seen using a low power eyepiece under dark skies.  Despite being relatively bright at magnitude 8.5, it has low surface brightest due to its large size.  There are many smaller, faint galaxies in this FOV.  More information about M101 may be found here.

Photographic Details:
Date:  April 30, 2008
Scope:  Vixen VC200L at f9 (FL = 1800 mm) on the Takahashi NJP Mount.
Autoguider:  SBIG ST-402 with Sky90 at f4.5.
Camera:  Apogee U32 -20C.

Astronomik Clear (unblocked) filter.
Exposures:  26 x 10' Total exposure 4.3 hours.
Conditions:  Transparency good; seeing (FWHM) approximately 3"; Temperature dropped to approximately 34 degrees F during the night.
Post-processing:  Calibrated, aligned, and Sigma Clip combined in Maxim.  DDP in ImagesPlus (IP).  Deconvolution in AIP4WIN as described above.  Further processing in Photoshop CS (16 bit format).

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