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 
Mexico.
        
        Music:  California Dreamin'