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Old 31-07-2012, 01:17 PM
ausastronomer (John Bambury)
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Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
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TPAS it's worth pursuing

Quote:
Originally Posted by gary View Post

Beyond AUTO ADJUST ON, Argo Navis has a powerful feature called the
Telescope Pointing Analysis System (TPAS) which is described in the Manual
under the section SETUP MNT ERRORS. However, before reaching for TPAS,
which is an advanced feature, you might find AUTO ADJUST ON is all you need.
Hi all,

I just wanted to add somewhat to Gary's comments here about TPAS.

I own 3 Argo Navis units which sit on 10", 14" and 18" dobsonians, two of which also have Servocat fitted. I am about to buy a 4th Argo Navis unit to sit on my new little 10"/F5.3 SDM; which should be in the mail within the next week or two.

I use the TPAS system religiously as it is an exceptionally powerful tool and can make a poorly built scope/mount, which would otherwise have poor pointing accuracy, in to one with superb pointing accuracy. Even a scope which points pretty well without TPAS can point a whole lot better with it. For instance my 14" SDM (which isn't poorly built and points well in any case) with TPAS can put targets into the centre of the FOV of my 7mm Pentax XW (230X and 18 arc minutes) each and every time. Similarly my 10" and 18" scopes point with similar accuracy once I have run a simple TPAS model on them.

What I notice in the field and at star parties is that a large number of Argo Navis users (probably > 90%) do not take the time to run a TPAS model. They centre the target at low power then change eyepieces. Putting the eyepiece into the FOV of the eyepiece you wish to observe it in can save you an enormous amount of time, particularly with galaxies and planetaries, where the planetaries may appear stellar at lower powers and you dont know if you have it or not.

As Gary indicates it is an "advanced" feature and there is a slight learning curve in learning how to get the best out of TPAS, it isnt' hard and offers significant benefits once you get your head around it. Consequently I would encourage people to at least "dip their toes in the water" with TPAS rather than putting it in the "too hard" or "can't be bothered" basket, once they become proficient in the main features of Argo Navis.

Cheers,
John B
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