California Nebula
The California Nebula derives its name
from its characteristic shape on long
exposure photographs.  This gas cloud is
located 2000 light years away in the
constellation Perseus.  It has a total mass
of 240 suns, and is illuminated by the
bright star to its right in this photo.  
Visually, this nebula is hard to observe even
with large telescopes, because its dim light
is spread over an area 4 times the size of
the moon.

The image on the left was acquired in the
light polluted skies of the northeast, using a
Hydrogen-alpha narrowband filter for
luminance, with an ST10-XME camera and
a 300mm Nikon f4.5 lens.  Exposure times
were 120 min H-alpha luminance, 15 min
R, 20 min G, and 21 min B.  The pure
H-alpha image is shown at the bottom of
the page.

For another comparison, I captured the
photograph below with a Pentax 300mm
f4.5 telephoto lens, Kodak 1000 speed
professional film, and a 20 minute exposure
in the clear skies of Cloudcroft New
Music:  California Dreamin'