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Herman,

The rules are the same as when using formula Sin Z = Cos Dec Sin t / Cos Hc

The prime vertical needs to be figured when near 90° or 270° 

Sin PV = Sin Dec / Sin Lat

The Z value is applied to 360° or 180° depending on whether Hc is larger or smaller than the prime vertical.

Greg  Rudzinski

From: Herman Dekker
Date: 2015 Sep 5, 13:26 -0700

Can some explain.

What are the rules for using the diagram determing Azimuth, when using the HavSinDoniol method.

I:The diagramscales go to 90°. So what to do for LHA:

0-90° use the scale

91-180°  ?

181-270° ?

271-360° ?

II:Then when found Z this gives value between 0 and 90°.

Some times added to 180° sometimes distrated from 180°

I have read the rule Z E/W as name of t ?????  t= LHA and is between 0 and 360° so, I do not see + or - on this.

Z N/S by observation, but what is to do, with one example from a textbook. Is there a rule for?

I think myself on something as: Declination Object  > Latitude Observer = N 0°    Declination Object < Latitude Observer = S 180°

or is that wrong?

I like written rules on the diagram, because I can difficult remember them If needed.

regards,

Herman Dekker