Ring of Fire Eclipse

These photos of the Oct 14, 2023 Ring of Fire (annular) eclipse were captured by long-time friend and astronomy colleague Roger Serrato. He’s actually had an asteroid named after him (25743 Serrato) for his work at Lowell Observatory in Flagstaff, AZ. Currently residing in Montrose, Colorado, he drove 100 miles to get to the path of annularity. The event only lasted a few minutes, as you can see from the time-stamps on the photo, after which it became a common partial eclipse. Here’s his camera info:

Canon 50D ISO 100 manual exp @ 1/30 sec., f6.3 16-200 lens @ 200mm
Camera and eyes protected by a Thousand Oaks Mylar® solar filter

His location for the photo was the red dot on the map below, about 20 miles south of Cortez, CO on the Ute Reservation off US Hwy 491. Had he traveled another 30 miles he would have been on the exact eclipse mid-line and the “ring of fire” would have been precisely centered around the black silhouette of the Moon. That shows you how sensitive these eclipses are to observer position.

Personally, I like a little asymmetry in photos like this … reminds one how fleeting these events really are. Check out my best shot of a Ring of Fire eclipse here:


For that photo I was around 40 miles from the exact mid-line, unable to find a good road to get closer — this was in rural New Mexico where there are sprawling ranches with fencing and gates. As the moment of annularity approached, we pulled over on the shoulder of a back-country road and set up our camera. We got lucky, as the overcast sky provided the necessary attenuation and we didn’t need our optical filter. That bought us some precious setup time.

This next map shows the full path of the 2023 eclipse over land in the Americas:

Given that 71% of the Earth’s surface is ocean, this was a remarkable eclipse in terms of how many people were favorably positioned to observe it. Of course, some areas were clouded out, but the American Southwest enjoyed clear skies.

It’s worth noting just why these types of eclipses happen, as compared to total solar eclipses. The Sun and Moon appear nearly the same size in the sky, with an average angular diameter of 0.5°. The Sun stays fairly constant in size, but the Moon’s size fluctuates. Depending on its distance from Earth (which varies along its elliptical orbit) the Moon’s size can range from 0.492° to 0.560° — a variation of nearly 14%. The angular diameter of the Sun ranges from 0.527° to 0.545° over the course of a year as Earth moves along its elliptical orbit, but that’s a variation of only 3.4%.

Here’s a video from my post: https://sky-lights.org/2012/11/12/how-the-moon-changes/. It shows several cycles of the Moon’s monthly variations. It’s a time-lapse recorded by NASA’s Lunar Reconnaissance Orbiter (LRO) over the full year of 2011:

Now you see why eclipses are sometimes total and sometimes annular. It just comes down to how far the Moon is from Earth when it passes in front of the Sun. The Moon is larger than the Sun most of the time, so when things do line up, most of the eclipses are total. Annular eclipses can only happen when the Moon is at or near its farthest point from Earth (apogee), so they are more uncommon.

Next Week in Sky Lights ⇒ Sidereal vs. Synodic Periods

Inferior and Superior Conjunctions
Sidereal vs. Synodic Periods