M33 (Pinwheel Galaxy)

All Images Copyright Steve Cannistra

Please click here or on image for a higher resolution view.

Magnitude:  7.0
Size: 73' x 45'
Distance: 3 million light years
RA: 01h 33m 47s
Dec: 30 degrees 39' 21"

M33 is a beautiful, large, and yet relatively faint spiral galaxy member of our local group.   Although its magnitude is 7.0, it has low surface brightness due to its large extent (over 1 degree).  The most conspicuous characteristic of M33 is the large number of HII star forming regions it contains, seen as red regions of Ha emission within the spiral arms.  One of these HII regions, known as NGC 604, is seen at about 7 o'clock in the above image and extends for over 1,500 light years.  More information about M33 may be found here.

Photographic Details:

Date:  November 3, 2004
Takahashi Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy Mount.
Autoguider:  SBIG STV with e-finder.
Camera:  SXV-H9
Astronomik Ha filter (13 nm bandpass); Type II R, G, B, plus clear filter set.
Exposures:  L:(HaR:G:B).  18 x 4' for Luminance (clear filter) (72 minutes total, unbinned); 7 x 5' each for Ha (35 minutes total, unbinned); 5 x 4' each for R, G, and B (20 minutes total for each color), all unbinned.
Conditions:  Temperature 36 degrees F; above average transparency; average seeing; a bit breezy.
No darks, flats, or bias frames used.  Alignment done in ImagesPlus.  Sigma combined using RC Sigma Reject Plug-in for MaximDL.  DDP was performed in ImagesPlus (IP).  Subsequent levels and curves adjustments in Photoshop CS (16 bit format).  The red channel was comprised of an Ha:R mix (100% opacity for R using lighten mode) in order to highlight the HII regions in the final image.

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