A rare eclipse

The moon from atop Mount John in April 2023 when the moon was just 3.1 days past new. PHOTO: IAN...
The moon from atop Mount John in April 2023 when the moon was just 3.1 days past new. PHOTO: IAN GRIFFIN
The moon is new tomorrow at 6.55am. For several hours around that time, people lucky enough to be in a narrow 200km-wide corridor crossing North, Central, and South America get to experience an annular eclipse of the sun.

Sometimes called a "ring of fire" eclipse, this event happens when the moon moves directly in front of the sun as seen from Earth. Because the moon is approaching its furthest distance from Earth, the lunar disk isn’t big enough to cover its parent star. Instead, during the maximum phase of the eclipse, the lunar disk is surrounded by a ring of light, making for one of nature’s most awe-inspiring spectacles.

Unfortunately, tomorrow’s eclipse is invisible from New Zealand; the next eclipse visible from our world is a partial one on the morning of September 21, 2025, when more than 70% of the solar surface will be covered by the moon, as seen from Dunedin.

While we won’t have a front-row seat to this particular eclipse, weather permitting, the next few evenings offer southern stargazers excellent opportunities to spot the very young moon. Tomorrow night, the moon will be pretty much invisible; its tiny crescent will be just 0.2% illuminated and sets just 30 minutes after the sun.

Prospects for seeing a young moon are much better on Monday night when the waxing lunar crescent is 2% illuminated and sets 100 minutes after sunset.

The 1.4-day-old moon will be about 15° above the western horizon at sunset and should be a remarkable sight as the sky darkens.

Hunting for young moons in the evening sky (and old moons in the morning sky) is one of my favourite astronomical challenges. I particularly love taking photographs of the moon against a backdrop of ever-changing twilight hues. That’s why I plan to take my cameras to a location with a great view of the western horizon to capture more images like the one accompanying this week’s Skywatch. The image was taken from atop Mt John in April 2023 when the moon was just 3.1 days past new.