Post by Centaur on Nov 13, 2016 10:31:28 GMT -6
Popular science publications such as Space.com get hyperbolic regarding so-called Super Moons, i.e. Full Moons near perigee which recur every 14 synodic months. So they’re making a big deal out of the one occurring tonight (Nov 13-14). In reality Super Moons’ angular diameters are not noticeably much larger than most Full Moons to casual observers.
However the particular point I want to make this time is that writers are calling this the biggest and brightest Full Moon for many years. It may be the biggest (greatest angular diameter) but not the brightest. The Full Moons of September and October were actually brighter. This was due to their being closer to the ecliptic and experiencing more of the oppositional flash effect. Another factor for brightness is nearness to the Sun. November’s Full Moon beats the earlier ones regarding this factor, but the ecliptic factor trumps that.
Below is a link to my Moon webpage where you will find data I compiled for Super Moons during the years 2015-2034 inclusive. I’ve listed both the ten Full Moons with the greatest geocentric angular diameters and the ten Full Moons with the greatest geocentric brightness ratios. Notice that only four in the diameters list also appear in the brightness list. In the cases of eclipses, the Moon has been shifted just outside of the penumbra.
The 1.0 standard for Full Moon brightness is that when:
1) the Moon is at its mean distance from Earth
2) the Sun is at its mean distance from Earth
3) the Moon is on the ecliptic
Of course that would be at the time of a total lunar eclipse. The standard assumes that the Earth is invisible. As noted, in the case of a lunar eclipse I adjust to give the brightness when the Moon is positioned just outside the penumbra.
Link to Moon webpage: www.CurtRenz.com/moon.html
However the particular point I want to make this time is that writers are calling this the biggest and brightest Full Moon for many years. It may be the biggest (greatest angular diameter) but not the brightest. The Full Moons of September and October were actually brighter. This was due to their being closer to the ecliptic and experiencing more of the oppositional flash effect. Another factor for brightness is nearness to the Sun. November’s Full Moon beats the earlier ones regarding this factor, but the ecliptic factor trumps that.
Below is a link to my Moon webpage where you will find data I compiled for Super Moons during the years 2015-2034 inclusive. I’ve listed both the ten Full Moons with the greatest geocentric angular diameters and the ten Full Moons with the greatest geocentric brightness ratios. Notice that only four in the diameters list also appear in the brightness list. In the cases of eclipses, the Moon has been shifted just outside of the penumbra.
The 1.0 standard for Full Moon brightness is that when:
1) the Moon is at its mean distance from Earth
2) the Sun is at its mean distance from Earth
3) the Moon is on the ecliptic
Of course that would be at the time of a total lunar eclipse. The standard assumes that the Earth is invisible. As noted, in the case of a lunar eclipse I adjust to give the brightness when the Moon is positioned just outside the penumbra.
Link to Moon webpage: www.CurtRenz.com/moon.html