NavList:

Hello Lars,

Thanks for your comment.

I know that the outcome of arccos C can be positive or negative.
But Frank teaches that it depends on the Zn of the clestial object.
In the morning AM the Zn is East then you must use positive sign.
In the afternoon PM the Zn is West you must use negative sign.
On the PDF I have written the sign rules in small text on the end of the line.

But I should have written it in different order.

Now I have followed the procedure that I have learned.
The standard rules are:
If Longitude >360° subtract 360°
If longitude <0° add 360°
This does not give me the proper solution with a value >180°.

Therefore it think I need only one other additional rule if the longitude value outcome is > 180°
If 180°<Longitude value<360° then Subtract longitude value from 360° the value is then

the East longitude.

Then Longitude 1= 173,76° E Longitude 2= 176,04° E

I want to know if this additional rule solves al the problems that can occur
with the general longitude sight.

Does Frank approve this?

Regards

HermanD