CharlesE wrote:What is the distance to the Super Moon tomorrow, at closest approach? What I'm really asking is for the distance variation between a micro moon (or from the average moon distance) and the Super Moon tomorrow.
: “The semi-major axis (average distance) is 384,403 km (238,857 miles). At its closest point (known as perigee) the Moon is only 363,104 km (225,622 miles) away. And at its most distant point (called apogee) the Moon gets to a distance of 406,696 km (252,088 miles).”
: “Perigee varies from 356,400–370,400 km (221,457–230,156 mi). Apogee varies from 404,000–406,700 km (251,034–252,712 mi).”
: “14 nov 06:20 EST - 356,509 km (221,524 mi)”
The Super Moon numbers are interesting in detail, though mostly academic. The variation in the geocentric distance of the full moon is more complicated than a constant orbital ellipse. The distance also depends on the it's position wrt the ecliptic, and where the earth is wrt the sun in its elliptical orbit (e.g. perihelion vs. aphelion). The sun and earth continually perturb the moon's orbit - the primary reason why the perigee has ~14,000 km variation in the Wiki article.
I used an Horizons-based ephemeris to tabulate all full-moon geocentric distances over 6000 years (-2999 to +3000).
=> The average full-moon distance = 381103 km
This is ~3000 km less than the Universe Today article which is significant compared to the 180-km difference between tomorrow's full moon the closest one over the 6-millenia of full moons.
Tomorrow's Super Moon has a geocentric distance of 356519 km (at the official full-moon time, ~2.5 hours after closest distance = 356508 km)
=> Tomorrow's Super Moon will be ~2.3 arcminutes bigger than the average, 6000-yr full-moon
=> Over 6 millennia, tomorrow's Super Moon is in the top 346 Super Moons
=> Wrt the largest Super Moon (at 356337 km), tomorrow's is smaller by only 1 arcsec!
=> Wrt the APOD 2012 Super Moon, tomorrow's will be bigger by only 2.5 arcsec
As a note, the 1948 Super Moon was in the top 249, and a still better one in 1930 was in the top 58. The next better one in 2034 is in the top 133. The next Super Moon closest to tomorrow's will be on Jan 2, 2018. It will be in the top 727 and be only ~1/2 arcsec smaller.
So don't feel too bad you missed the biggest Super Moon, tomorrow will be about as spectacular as they get - Not very different