Talk:Sar (astronomy)

Proposed text for future stub article*
(*assuming I can find citations (which should come from saros (astronomy).)

"A sar is a period of 111.5 synodic months (111 synodic month plus one fortnight, or very close to 9 years 5 and a half days). It can be used to predict solar and lunar eclipses. It is exactly one half a saros. After one sar if a solar eclipse occurred a lunar eclipse will always occur and vice versa.

-- Details --

Because it is half of a saros, the sar has 119.5 anomalistic months. Because of this half anomalistic month (which tracks the moon's progression from perigee to perigee) the moon will have shifted 180° with respect to the apisides. Because the period includes one fortnight (half a synodic month) the phase of the moon will also be opposite what it was the last sar, (full instead of new and vice versa). Because it contains an even number (121) of draconic months, the eclipse will occur at the same node. Thus, assuming the earth is at its aphelion, if the moon was at its perigee, new and very close to a node at the last sar, a total eclipse of long duration will have occurred somewhere on earth. One sar later, the earth will still be at its aphelion, but the moon will be at apogee and full moon at the same node. The relative diameter of the moon now being small, this will guarantee a total lunar eclipse of long duration on the opposite side of the earth.

-- Related lunar and solar saros series --

Lunar saros that are one sar apart from a particular solar saros have the same series number minus 7. These two saros series form a pair with one event every sar alternating between the lunar and solar series. Each series will have nearly an identical number of members, and begin peak and end at the same time.