Lunar eclipse to start year
January 16, 2018
The main event in our sky this month is a total lunar eclipse on the night of January 31st/February 1st.
It will be visible throughout New Zealand and there's a fair chance of seeing a "blood moon". This happens when light from the Sun gets refracted through Earth's atmosphere, turning it red before it hits the Moon. Blood moons depend on atmospheric conditions on Earth and are therefore unpredictable. The Moon might turn fiery red, it might only achieve a dull shade of red or brown, or it could be a complete dud. We'll have to wait and see.
Unfortunately the eclipse begins near midnight, you won't see much until 1 am (1st Feb) and you'll need to wait until at least 1:45 am to see the full effect. The total part of the eclipse lasts from 1:51 am to 3:08 am.
There are different types of lunar eclipse but all of them happen when Earth passes between the Sun and the Moon, casting a shadow on the Moon.
Partial eclipses, when the Moon is only partly in Earth's shadow, happen every year and are moderately interesting. Total eclipses, when the Moon is completely within Earth's shadow, are less common and more fun.
The January eclipse is even more rare as it happens to be a total eclipse, blue moon and supermoon all at the same time. This doesn't really affect what you'll see but it's an interesting coincidence.
The term "blue moon" usually refers to the second full moon in a single calendar month, something that happens once every two or three years. It doesn't affect the Moon's appearance at all.
A "supermoon" is when a full moon occurs at the same time that the Moon's orbit brings it closest to Earth, causing the Moon to appear a little bit larger. There are several supermoons per year.
There is another lunar eclipse in July but don't get excited about that one. Weather permitting, January 2018 will be the best eclipse until May 2021. Put it in your diary now.