NavList:

Steve,

That's right. When you do any type of sight reduction, you are solving for the alitude and azimuth of a body using an assumed position. Any sight planning or sky mapping tool is doing the same thing, except with multiple bodies at once. The claculated azimuths of the bodies at the assumed position directly determines the orientation of the resulting LOPs. The calculated altitudes, when compared with the observed altitudes, determines the distance of the LOPs from the assumed position. So, if you choose two bodies from a sight planner which are 45° apart in azimuth, the resulting LOPs will cross at 45°. Likewise, two bodies whose azimuths are 90° apart will yield LOPs which cross at 90°. The LOPs will always be perpendicular to the azimuths.

The only "special case" is when using a body that is near the zenith. When doing so, it may be necessary to use a table of offsets to produce a 'curve of position'. If the body is very near the zenith, you can even use a compass to draw a circle of position. However, in either case, the position curves or circles should still intersect at an angle close to the difference in azimuths. But this is one reason that using a body near the zenith is generally not recommended.

Regards,

Sean C.