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Old 03-11-2010, 10:19 AM
gary
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Join Date: Apr 2005
Location: Mt. Kuring-Gai
Posts: 5,914
Argo Navis encoder direction sense signs on A Dob

Quote:
Originally Posted by nightstalker View Post
Hi Gary

Ok , so I power up and fix the alt ref as always no problems
go to aligna stars, warp factor both come up as zero as I recollect they always do ?...Move on to find object and its nowhere near the right bit of sky .

Start over .. fix alt ref.. move on to check encoders
as far as I can tell through all movements things appear normal
and alt movement is always parking back at 90 or very close .
After alignment I check the encoders and alt can be reading maybe 110 or more.
Hi Graham,

It could simply be that one of your encoder direction sense signs is reversed.

The encoder direction sense signs are the +/- signs in front of the
encoder step counts in SETUP ALT STEPS and SETUP AZ STEPS.

It may well be your Az sign, but here is a procedure to check both.

To determine the Alt sign, power the unit ON and push the Dob
to its vertical stop. When the MODE FIX ALT REF menu appears,
press ENTER and dial up a value of ALT REF=+90 AUTO ADJUST OFF.
Press ENTER to establish the point.

Now EXIT out of that menu and dial up MODE ENCODER and press ENTER.

Observe the right-hand displayed value.
Initially, it should be +90. As you move the OTA down in Alt
only toward the horizon, it should decrease, +89, +88, ... +1, +0.
If it increases, i.e. +91, +92, then reverse the SETUP ALT STEPS sign and
repeat the procedure.

To determine the Az sign, dial up MODE ENCODER and rotate the scope
clockwise in Az from the perspective of looking down at the scope from above.
The left hand Az value in MODE ENCODER should increase, if not reverse
the SETUP AZ STEPS signs and repeat the tests.

Once the signs have been determined, enter a value of +090.00 into
the MODE SETUP, SETUP ALT REF menu. Then next time you perform the
MODE FIX ALT REF step, use a value of +090.00 AUTO ADJUST ON.

Since the AUTO ADJUST ON setting adjusts your ALT REF point based on
your two star alignment, if the alignment is wrong, for whatever reason, the
ALT REF point will not be correctly determined. In the absence of any mechanical
problem such as a slippage, a misidentified star or an incorrect encoder direction
sense sign combined with AUTO ADJUST ON would best account for why your
ALT REF point changed so much after the alignment.

Please don't hesitate to email or phone should you require further assistance.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Phone +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

Last edited by gary; 03-11-2010 at 09:07 PM.
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