[AZ-Observing] Astroimages from Cherry Road

Last Saturday night at Cherry Road, I put the imaging equipment through its 
paces.  This began innocently with me purchasing an equatorial mount to track a 
Pronto.  Now I am finding that it does an acceptable job of tracking both that 
scope and a piggybacked camera with 200mm lens.  

I have promised myself not to get back into imaging through a telescope, with 
all of the frustrations that effort brings.  So for last Saturday night, the 
Pronto was a glorified guidescope.  The images were taken with a Canon Rebel 
300D digital SLR.

Images here:

http://www.pbase.com/polakis/cherry200508


...and comments, in case you care.

The camera is fine out to 2 minutes, and noisy at 4 minutes.  The best way to 
do increase exposure time is to co-add a number of 2-minute exposures, but 
that's too much work for now.  The 20D has a dark-frame feature.  ISO 400 seems 
to be the best setting, but 800 is a close second.

Thanks to Frank Kraljic for lending his 20D to take the first image of the 
equipment and Big Dipper.

The 50mm lens is f/1.8, and a full stop down is not quite enough.  Notice the 
coma in this cropped image.  I think it will be fine at f/4.  I am pleased with 
the level of detail around the Large Sgr Star Cloud, including tiny Barnard 86.

The 200mm lens is actually the 70-200mm L series lens, and it's damned near 
impossible to focus.  After 8 iterations (5 second exposures magnified on the 
review screen), the focus is still not quite right in these images.  I think 
the 200mm is the upper limit for manually guiding a stock SkyView Pro mount 
such as this one, and maintaining sanity.

Two images were taken with a 20mm lens, which is a nice piece of work by Sigma. 
 That lens shows very little vignette or coma one stop down from wide open 
(f/2.0).

I love fisheye lenses.  The 8mm is again a Sigma, and one of only two choices 
for Canon, the other being a Peeleng, made in Belarus.  This one works fine 
wide open, at f/4.0.  The light dome from Phoenix has not changed much over the 
years.  Not in the frame is the very objectionable, growing light dome from 
Prescott to the west.

Having just finished Scott Kelby's excellent "Photoshop for Digital 
Photographers", I will be moving on to Jerry Lodriguss' "Photoshop for 
Astrophotographers."  Hopefully the result will be less uneven contrast and 
color balance.

Tom

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