Thanks for the posts.
The most important function of any telescope pointing device is
to assist the user in achieving their own stated pointed
performance goal.
For example, for many visual observers, the pointing goal might
be articulated to be to drop the object within the FOV of the
eyepiece of choice across the whole sky. For imagers, the goal
might be to blind point the scope so as to deliver the object
onto a small CCD array.
When going from the cataloged co-ordinates of some object, such
as a star or galaxy, to where the telescope computer 'thinks' it
is, requires a complex series of transformations. For example, the
effects of precession and nutation of the Earth, atmospheric
refraction and so on result in the apparent place of an object
being different to its cataloged position. Another potential
source of error is the various geometric, gravitational flexure
and eccentric bearing errors within the mount/OTA. Devices such
as mechanical setting circles and Digital Setting Circles (DSC)
do not take effects such as precession, nutation and refraction
into account and any geometric error within the mount compounds
the problem so that the pointing error residual might become
significant enough that the system does not achieve the
end-user's pointing goal.
Argo Navis is a Digital Telescope Computer (DTC) rather than a
DSC. This is an important technical distinction rather than a
marketing one.
Unlike a DSC, the Argo Navis DTC takes into account effects such
as precession, nutation and refraction and through its
Telescope Pointing Analysis System (TPAS) can assist the user in
helping to diagnose and potentially compensate for some of the
more common systematic errors that occur within a mount/OTA.
All mounts, even the Kecks and Gemini telescopes, have geometric
fabrication errors to some extent. For many amateur enthusiasts, the
errors are sufficiently small on their telescopes that they achieve their
pointing goals without needing TPAS. Therefore, like a cure for
some ailment, TPAS is certainly does not need to be prescribed
to everyone. However, for those with chronic systematic pointing
problems, TPAS can often be a great benefit.
Over the coming weeks I will attempt to make some posts walking
one through the various steps of TPAS.
Also be sure to attend my talk at the forthcoming South Pacific
Star Party where you can learn more about telescope pointing.
Best Regards
Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au