# The Moon's apogee (manda) and the anomalistic month — its varying distance
model.geocentric
reset
show.bodies
show.moon
show.moonApsides
show.orbitRing
now
overlay.show The Moon's orbit is not a circle about the Earth — its distance changes through the month
overlay.show Nearest is perigee, furthest apogee; the line joining them is the line of apsides
wait.next Run it through several months

overlay.clear
speed.set 10
repeat 6
  play.until.perigee
  overlay.clear
  overlay.show {date} · {moon.apsis} · apparent size {moon.size}
  wait 1.2
end
pause
overlay.clear
overlay.show Perigee to perigee is the anomalistic month — about 27.55 days
overlay.show It is longer than the sidereal month because the apsidal line is itself creeping forward
wait.next So what did Āryabhaṭa do with it?

overlay.clear
overlay.show This varying distance is what the manda correction accounts for
overlay.show It is also why eclipse magnitude differs: the same shadow meets a Moon of changing apparent size
wait.next Done

overlay.clear