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Dear Stephen,

You shouldn't bother with multiple APs using Pub. 249 for plotting. You have several alternatives:

1. Clone yourself and your instruments and take all your sights at exactly the same instant. This way all sights will have the same LHA Aries and thus the same AP longitude could be used.

2. Separate your sights exactly by 4 minutes. Since four minutes of time equals one degree of arc (hour angle), all your LHAs will have the same fractional part: a single AP could serve for all.

3. For irregular timing of the sights, you can compensate the intercept for time differences. Use the Motion of Body (MoB) tables for the compensation. If you're flying fast, you may need the Motion of Observer (MoO) table too :-D, but for now ignore it. (Or alternatively, more sophisticated tools like the Polhemus computer, but for a stationary or slow-moving observer such a computer won’t give too much advantage.)

Obviously, Option 1 is a bit difficult to perform, so I recommend starting with Option 2. When you have enough experience and confidence with it, you may move towards Option 3.

Read the manual at the beginning of Pub. 249, Vol. I. The latest Celestaire edition writes:

"In more complicated plots with more LOPs than this simple two-body case, the presence of multiple AP
positions can become confusing. Two procedures are available to simplify plotting and use a single AP position
for all sights:
Timed sights. By taking individual star sights at intervals of four minutes as nearly as possible, usually timed
by an assistant or with an audible alarm, the same AP longitude will emerge for each sight since the minutes of
GHA Aries cycle through one whole degree in almost exactly four minutes.
MOB Adjustment. Sights taken over a period of up to 30 minutes can be synchronized to one common time
using the Motion of Body calculation (details below). The UT of the first or last sight in a set is treated as the
common time for all sights, and the observed altitudes are shifted up or down to account for the rotation of the
Earth during the intervals between sights. Reduced to a common time, all sights then have the same GHA Aries and
thus the same AP longitude and LHA Aries." Examples and methods are described in later paragraphs.

Please note that earlier editions (epoch 2020, for example) had a different introduction. They may be worth reading too in the section titled “Special Techniques.”

Three sights should be enough for one plot. Because observations are spread in time, they introduce some error: the more the sights, the wider the time span, the larger the introduced error. More sights may not compensate for it or may even make things worse, and the delay from observation to fix is extended.

Best regards,
Tibor