Re: [APML]: polar alignment

[Brad Wallis <wallis@pepe.jpl.nasa.gov>]

polar scopes ... when used on a well constructed mount ... are only useful
for short exposures  with most FL lenses or scopes ... the may work
OK with a 50mm lens for a 1 hr shot ... ... not sure where the cutoff
is ...

these are emant for a preliminary setup and  preliminary polar alignment ...
they may work OK with short 5-10 min CCD shots or short color shots of
5-10 min duration ...

beyond that you need to drift align ....  the advertising hype for these
things is just that ... HYPE ...   

i really urge you all to write letters about all the over hyped gadgets
that your favorite astronomy magazine pushes ... maybe a lot of 'backlash'
would clean up the advertising ... we might not get catalogs from SCT
makers that claim 'the best optics produced anywher in the US' if the
readers and users started to let the astro-rags know that they are just
plain fed up ....  

using a polar scope prior to drift aligning will save you a bunch of time 
... at least if your mount is well made and well aligned with the axis
of the polar scope ...   you wil find that using a polar scope produces
the worst results in ALTITUDE which affects horizon shooting .. this is
due to refraction effects...

Brad Wallis

there is a HINTS piece on poalr alignment at our web site :
     http://voltaire.csun.edu/wallis_provin.html