Sir, – According to The Irish Times, "the blood moon is a rare celestial event in which Earth appears in a straight line between the moon and the sun" (News, July 25th).
What is being described is a total lunar eclipse – a relatively common occurrence with the next one visible from Ireland within six months.
The term “blood moon” entered the mainstream in 2014 via two Christian ministers who delivered an apocalyptic prediction relating to four consecutive total eclipses.
Aside from its dubious origin, blood is a poor descriptor, as the colour of a total lunar eclipse can range from dark grey to rust-red to bright orange, depending on a multitude of factors. Indeed there is a measure, called the Danjon scale, to record such variations. – Yours, etc,
DANIEL LYNCH,
Dublin 6.