Quote:
Originally Posted by MattT
All done! Gone steampunk with encoder brackets....now to learn haow to use it.
I have read every post here and I'm not sure how exact the GEM exact align is. Is 1º of the pole exact enough? or is that rough align territory? On page 16 Clive seems to be the only GEM AN user.
Here is my mount with AN fitted.
|
Hi Matt,
Absolutely wonderful implementation and I loved how you kept it looking antique.
What we recommend these days is to consider using the GEM EXACT ALIGN setting in conjunction with what we call
a short TPAS run. TPAS stands for Telescope Pointing Analysis System, which is an in-built feature of Argo Navis that
appears under the SETUP MNT ERROR functionality.
To use this technique, set the GEM EXACT ALIGN setting in SETUP MOUNT and set your latitude and longitude accurately in SETUP LOCATION.
Also set your time accurately either from SETUP DATE/TIME or better still via your PC running an NTPS client and using Argonaut Version 2
(see page 188 of the Edition 11 of the Argo Navis User's Manual).
Align on one star and then use TPAS to sample the position of at least four stars (see pp 122-149 for a description of how to use TPAS
in the section of SETUP MNT ERRORS).
With the press of a few buttons, one then fits a mount error model that includes the polar misalignment terms in azimuth and elevation and
and what are called the index error terms for the RA and Dec axes. The polar misalignment terms are abbreviated as MA & ME.
The Index Error terms are abbreviated as ID & IH.
In practice this takes probably less than five minutes. It then typically results in excellent pointing performance because Argo Navis
is mopping up any residual polar misalignment in its pointing model. Dropping the mount down within a degree of the pole,
using the GEM EXACT ALIGN setting and combining it with a short TPAS sampling run will typically ensure everything lands
in the FOV without having to do a FIX ALT REF step.
What is also good about this approach is that it is extensible. All mounts have a certain amount of geometric and gravitational
flexure errors that can be a detriment to their overall pointing performance.
The TPAS system allows you to analyze and potentially compensate for many of the common geometric and flexure errors
within the mount/OTA. For example, you might devote one night, perhaps when the Moon is out. to sample say 20 to 50
stars and to use the in-built TPAS to analyze the data for any likely persistent mount errors. You can then store these
parameters in the unit as a mount error model. On a subsequent observing night you can re-synchronise this model by sampling
as few as four stars and your pointing performance will typically return to as good as the night you did the long sampling run.
So you can think of TPAS a "super N-star alignment" but really it is much more than that because of its complex modelling.
Otherwise there is a little bit to take in here and I don't want to make your eyes glaze over with it all at once, but I cannot over emphasise
how quick and convenient it is to use the EXACT align setting in conjunction with a short TPAS run is in practice.
The link to a case study of an Argo Navis Telescope Pointing Analysis System (TPAS) sampling run on a G11 mount will be of interest -
http://www.wildcard-innovations.com.au/group_post_5573/
Should you have additional questions or require clarification on any of the above, please do not hesitate to contact me.
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