I read that some rare eclipses are hybrid, where it can be annular near the beginning and/or end of its journey over the Earth's surface, and total in between. That begs the question, if a person is in the right place, can they witness both? Since the duration of a total/annular never exceeds a few minutes, I guess even if it's possible, the transition between 2 states will be very short.

Has anyone in the world ever seen both states in 1 outing? Are there photos of the event? Theoretically, can we calculate the typical area of the strip of land where both can happen? Is it possible to find out about that in our normal media coverage (i.e. the internet for non-experts) of eclipse?


1 Answer 1


I'm going to say "not possible". Hybrid eclipses do occur as the curved surface of the Earth isn't a fixed distance from the moon, and so the distance from the point on the Earth's surface to the moon isn't constant. But the moon's transverse motion is much greater. To achieve an annular->total eclipse in one location, the "back" limb of the moon would have to be moving in the opposite direction to the front limb (relative to the sun). This would be possible if the moon was rapidly approaching us. In that case the increase in apparent size of the moon would be so large that one edge of the moon would appear to move east, while the other appears to move west.

But this doesn't happen. Both limbs of the moon move east, relative to the sun, perhaps with one limb moving very very slightly faster than the other due to the radial motion of the moon. As both limbs are moving in the same direction, they can't go from being both within the solar disc to both outside the solar disc. And so there is no fixed location that could experience an annular eclipse becoming total.

You could only see both an annular and a total eclipse if you move your location during the eclipse, in an aeroplane, for example.

At the point of transition, you may see a complete set of Bailey's beads, as the sun shines through valleys on the moon's limb.

enter image description here
Sourced from http://www.naasbeginners.co.uk/News/SolarEclipseMarch2015.htm

That is about as close as you can get to being "both annular and total" (but it counts as "annular", if anyone is keeping track).

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    $\begingroup$ I think one case to consider is an observer viewing an eclipse at sunrise/sunset. At the equator, that person would be moving about 1000Mph towards or away from the moon. I think it's conceivable an observer could move from a distance of annularity to totality. I doubt there's an eclipse where this actually happens though. $\endgroup$ Jan 7, 2023 at 16:50
  • $\begingroup$ But even then the moon is moving transversely at over 2000 mph, I think the transverse motion always "wins" $\endgroup$
    – James K
    Jan 7, 2023 at 17:08
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    $\begingroup$ Here's my napkin calc. Assuming a long totality of 2mins, that translates to 50km of 'gain' for a person at the equator looking at sunrise/set. That corresponds to ~0.13% change in angle in apparent diameter. So at best, a totality will change to/from just a few tiny Bailey beads. Yet it could mean a 50-fold change in brightness! $\endgroup$
    – longtry
    Jan 8, 2023 at 8:43

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