JSCalc

Unless you forget that the sky spins, right ascension feels backwards. Latitude and longitude are our measurements on the planet; up there, they use its … Read More

There is a spot in the sky with some light on it. It is a fuzzy smudge. What’s that? Oh yeah, you want to look … Read More

We live with a coincidence: The Moon and the Sun are about the same apparent size in our sky. They are not actualy the same … Read More

Orbital mechanics determine size of umbra, and that, in turn, tells us how large a shadow will be. That means you can use the umbra … Read More

The big moment arrives, it’s a full moon, you look up and ask yourself: How long will this eclipse be? You set alarms for the … Read More

That’s the particular sort of dashed hope that eclipses bring: you drive to your appointed spot and discover it wasn’t enough; the sky turned black … Read More

Publicity surrounds eclipses, but even veteran eclipse watchers may get confused by their numbers. Maybe there’s a prediction stating that it’ll have a magnitude of … Read More

Sometimes the moon seems bigger then other times. Yes, it does! But you aren’t crazy; sometimes the moon is closer to us (and so appears … Read More

There is something satisfying about watching the moon go through its changes. It’s a slow process which means that on any one night you’re unlikely … Read More