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Old 25-02-2009, 02:11 PM
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gary is offline
Join Date: Apr 2005
Location: Mt. Kuring-Gai
Posts: 5,437
Arrow To check SETUP AZ, move in Az

Originally Posted by nightstalker View Post
I'll check the pole sweep again .. I'm going from a point alittle east of canopus and sweeping down to the east through altitude motion .?.
Hi Graham,

For checking the SETUP AZ STEPS sign, avoid that part of the sky.

Why is that?

From your latitude there in Victoria, stars between approx. Canopus and the
SCP are all circumpolar. What this means is that if you sweep easterly
from stars north of the SCP, RA will increase, but for those between the
SCP and the southern horizon, RA will decrease.

So there is room for uncertainty in those polar regions when performing a check.

Better to sweep along near the Celestial Equator. This time of year, think
Orion's Belt, think Rigel, think Betelgeuse and even Sirius and Procyon
as the starting points.

The purpose of this check is to ascertain the encoder direction sign
for the Az encoder. You have already determined the sense of the
sign for the Alt encoder using the FIX ALT REF +90, MODE ENCODER
procedure. Though from your latitude you can't move the Dob along the
Celestial Equator without moving it in both Az and Alt *, the primary purpose of this
step is to ensure motion in the Az axis, because that is the axis you are

Whereas you use MODE ENCODER to check the Alt sign you are using
an alignment followed by a check of the left-hand display in MODE RA DEC
to check the Az sign.

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

* If you were standing at the geographic South Pole, you could move
the scope in Az only long the celestial equator, which in that case would
be pointing on the horizon. As a side-effect of physically moving your Dob
to the geographic South Pole, it will transform itself into an equatorial mount.
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