Celestial Navigation with RFB / TMO mods?

[Sean C]

Originally Posted by Rockin Robbins

The phase of the moon is directly related to its rise and set times.

No, it isn't. The phase of the Moon is a function of its apparent angular separation from the Sun. The percent of illumination can be calculated as the haversine¹ of the separation angle in degrees.

The apparent angular separation can be calculated using the following formula:

θ = acos(sin(Dec1)⋅sin(Dec2)+cos(Dec1)⋅cos(Dec2)⋅cos(G HA2-GHA1)) (Not sure why there's a space inserted into "GHA2". I can't remove it.)

If the Moon was only 10 degrees from the Sun, it should be a crescent. A very thin sliver at 0.7% illumination, but a crescent nonetheless.

¹Haversine = (1-cos)/2