Supermoon Total Lunar Eclipse 2015



A total lunar eclipse will take place on Sunday night from Europe and Africa, across the Atlantic to the Americas and eastern Pacific, as the moon passes through the Earth's shadow. The eclipse will also coincide with the moon's closest approach to Earth on its elliptical orbit (perigee). Coined the 'supermoon', the moon can appear up to 14% bigger and 30% brighter than its counterpart, the 'micromoon' (where the moon is at its furthest point away from the Earth on its orbit, called the apogee).

NASA explains how supermoon lunar eclipses occur

The eclipse in the U.K. will be fully visible (weather-permitting) and will occur during the early hours of Monday morning, the entirety of the event beginning at 01:11 BST in the southern sky and ending at 06:22 BST above the western horizon. The partial eclipse will commence at 02:07 BST (when the moon will begin to turn red), leading to the total eclipse from 03:11 BST to 04:23 BST (during which the moon will appear completely red, for a duration of 1 hour 12 minutes). The moon will reach maximum eclipse at 03:47 BST.

Click on image to enlarge

The above graphic highlights the key points of the eclipse, and time of occurrence, plus gives an indication of where in the night sky to be looking to catch a glimpse of the moon throughout the event. With high pressure across the British Isles, centred over the North Sea, we remain optimistic some parts of the country will see it, although it is too early to speculate where the best clear spells may be.

Supermoon lunar eclipses are quite rare - the most recent one occurred in 1982, and the next will be in 2033. The next total lunar eclipse in the U.K. will be in July 2018, but the beginning of this event will occur before moonrise.

Dan Holley  24th September 2015


Equinox: Why day and night are not actually equal

Today marks the autumn equinox, the point in which the centre of the sun is directly over the equator, and thereafter will be centred over the Southern Hemisphere. Equinox derives from latin for "equal night", and while the sun spends roughly an equal amount of time (12 hours) above and below the horizon across the Earth, the length of the local daylight is not equal to the hours of darkness.

The reason for this is because we measure sunrise to be the time at which the top of the sun becomes visible at/above the horizon, and likewise sunset is when the top of the sun vanishes at/below the horizon. The centre of the sun is still yet to reach the horizon in the case of sunrise, and equally goes below the horizon before sunset.

This added time at sunrise and sunset means the day is actually still longer than the night at the equinox, and in the case of East Anglia today's day length is approximately 12hours 10minutes. Hence, "equal day equal night" is more applicable, in terms of how we measure sunrise and sunset, a couple of days later, i.e. 25th September where day and night are roughly 12 hours apiece. Likewise in spring, it will be a couple of days before the vernal equinox.

Click on image to enlarge

Dan Holley  23rd September 2015