ATM Alt/Az/FR Piggyback Autoguider a Success

[Al Kelly <akelly@ghg.net>]

Hi Folks,

        After much designing, building, and tweaking, the piggyback
Alt/Az/FR (focal rotation) autoguider system on our Danciger 32" f4 Newt is
finally working as conceived...:).  The system uses an ST4 as the
autoguiding camera and an 80mm f15 refractor as the guidescope.  The
piggyback system is built around an axis of rotation which is driven at the
same rate (and by the same signals) as the field rotator of the main scope
drive.  This has been a while coming and now allows much longer individual
subexposures to be made.  
        Last night, Ed Grafton and I made the final system tweaks and made
WCMY subexposures with my CB245 of NGC 6907 with the 32 in autoguide mode.
We used 2-minute subexposures, but could have easily gone longer had we not
wanted to avoid blooming of a bright field star.  Previously, the longest
usable subexposure time with the unguided 32 had been about 30 seconds.  We
made ten W (IR-blocked), 6 C, 5 M, and 4 Y subexposures.  All 25 2-minutes
images were well tracked and were used to composite the final true color
WCMY image of this rather innocuous but very esthetic 4-arcminute galaxy,
which can be seen at http://www.ghg.net/akelly/6907larg.jpg .
        Chuck Shaw, Ed Grafton, and I (with design encouragement and inputs
from Andy Saulietis) have been thinking about and working on this for many
months.  Chuck has been the primary contributor, doing a *great* job of
basic design and construction of the piggyback assembly!  See a webpage on
this effort on Chuck's website at http://www.ghg.net/cshaw/guiderot.htm .  
        We believe doing something like this is THE way to finally turn all
the current era's amateur alt/az behemoths into true imaging systems!

Regards,

Al K.
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Al Kelly .... e-mail: akelly@ghg.net 
         .... web site: http://www.ghg.net/akelly/

"Before criticizing a man I walk a mile in his shoes. 
 That way, if he gets mad, he is a mile away and barefoot."
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