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Comment by higgins | Hacker News Reader

> On 12 December 2023 Leona will occult Betelgeuse as seen from southern Europe.

> On 12 December 2023 at about 01:09–01:27 UT, Leona will occult Betelgeuse as seen from southern Europe, Turkey, Greece and Sicily.[14] The 14th magnitude asteroid will occult Betelgeuse (block or reduce the light) for about 12 seconds. Betelgeuse is expected to dim by about 3 magnitudes.[16] Light curve studies of the event may help understand the distribution of brightness over the disk of Betelgeuse.

Betelgeuse is the 10th brightest star. It's dimming by a factor of ~16, but will still be visible, which surprises me. Does anyone know whether this is because (a) Betelgeuse's diffuse disc is wider than the asteroid's, (b) Betelgeuse will refract around the asteroid, or (c) something else? I'm guessing (b) but don't know much about this.

Per wikipedia, dimming by 3 magnitudes means Betelgeuse will still be at +3-+4.6, which is probably too dim to be seen in a city, but still plenty bright.

The primary source of the 3 magnitude dimming is this data: https://www.asteroidoccultation.com/2023_12/1212_319_82912_S...

It seems to be based on a very crude estimation, see the data near the bottom. It estimates Betelgeuse to have an angular diameter of 48.10 milli-arcseconds, and the astroid's angular diameter to 46.0 milli-arcseconds, which works out to a 11.7 dimming factor.

But the summary there says this?:

> In the case of an occultation, the combined light of the asteroid and the star will drop by 13.72 mag to 14.22 mag (the magnitude of the asteroid) for at most 11.620 seconds.

Which suggest complete blockage of the star's light.

> This section needs expansion with: details about the unusual occultation. You can help by adding to it. (May 2022)

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