A rare astronomical event it’s about to happen in the night between September 17th and 18th: the second of four consecutive full moons “supermoons” (the first was on August 19), known as “Harvest Moon”will in fact be accompanied by apartial eclipse of MoonThe partial eclipse will have its maximum around 4:44 on the morning of September 18, when approximately 9% of the lunar disk will be obscured by the shadow cast by the Earth. The coincidence of the eclipse with the “Supermoon”, a journalistic term coined to indicate a full Moon that occurs when it is within 90% of the perigee, makes the astronomical event particularly rare and not to be missedsince our satellite will be larger (up to 10%) and brighter (up to 30%) than a normal full Moon. The eclipse will be visible to the naked eyealthough the small fraction of the obscured lunar disk leads to recommend using binoculars to fully appreciate the event. It is also not necessary to move from inhabited centers given the high brightness of the Moon and its position of approximately 25 degrees above the southwest horizon at the moment of maximum eclipse. The Moon will not be alone in the sky, but will be accompanied by Saturn which will escort her throughout the night, preceding her on her path across the celestial vault.
What is a partial lunar eclipse?
The lunar eclipse occur when the Earth comes between the Sun and the Moon, preventing sunlight from reaching a part of the lunar surface, which is then in shadow. The geometry of the Sun-Earth-Moon system ensures that the lunar eclipses may happen only during the full moon phasethat is when the face of our satellite turned towards us appears completely visible to us. They do not occur every month since the floor where lies theThe Moon’s orbit is slightly tilted (about 5°) from the plane of the Earth’s orbit, so the Moon is often full when it is outside the shadow cast by the Earth.
The lunar eclipses (but also solar ones) can be totalthat is, when the entire celestial body is within the shadow cone cast by the Earth, or partialthat is, when only a part of the celestial body is covered by the Earth’s shadow. The event of September 18th it will be a partial eclipseso only a part of the lunar disk will be in shadow, the8.7% to be precise.
When will the partial lunar eclipse occur?
The astronomical event will take place in night between Tuesday 17th and Wednesday 18th SeptemberThe exact moment when the Moon will be in its full Moon phase at its closest approach to the Earth, defined “Supermoon”it’s at 4:35 in the morning on September 18, about 10 minutes before the maximum of the partial eclipse.
The entire eclipse phase begins at 2:40 in the morningwhen the Moon, at 35 degrees above the south-southwest horizon, enters the penumbra generated by the Earth. This is the so-called phase of penumbral eclipseless spectacular and clearly visible only 20-30 minutes after 2:40. The partial eclipse real and proper start only at 4:12 with the Moon entering the shadow cone cast by the Earth. The beginning of the partial eclipse occurs when the Moon is approximately 28 degrees above the south-west horizon, while the maximum of partial eclipse occurs when the Moon is about 23 degrees above the horizon at 4:44 in the morning. The lunar disk will be obscured by the shadow cast by the Earth for only 8.7% of its entirety in the north-eastern limb of our satellite. The event ends first with theMoon’s exit from the shadow cone of the Earth to 5:16and subsequently with thealso exited from the penumbra cone to the 6:47when the moon has already set below the horizon.
How and where to observe the partial lunar eclipse in Italy
The concomitant event of “Supermoon” and partial lunar eclipse can be observed with the naked eyeThe high lunar brightness in the full Moon phase, increased by the proximity to the perigee, and the height above the horizon (about 25% in the maximum phase of the eclipse) also mean that the event can be appreciated even from the city skies. Despite this, we feel we can advise you to equip yourself with binocularsThe reason lies in the small fraction of lunar disk covered by the shadow cast by the Earth, only the 9%. Unless you have excellent eyesight, it will be difficult to spot with the naked eye the small crescent Moon obscured by the Earth’s shadow in the Northeast edge of our satellite, while using binoculars makes everything much simpler and more enjoyable.
What is the “Harvest Moon”
“Supermoon” is a journalistic term – therefore it is not part of the technical astronomical jargon – coined in 1979 by the astrologer Richard Nolle to indicate a full Moon that occurs when our satellite is within 90% of its maximum approach to the Earth (the so-called “perigee”). They are therefore the largest (up to 10%) and brightest (up to 30%) full moons of the year.
This particular “Supermoon” is called “Harvest Moon”as it is the full Moon closest to the autumn equinox. The first known written use of this name is from 1706, and is related to the fact that during the autumn harvest season, farmers sometimes had to work late into the night under the moonlight. Since moonrise does not coincide exactly with sunset, around harvest moon days, the difference in minutes between moonrise and sunset is minimal, allowing farmers to continue working under the moonlight.
