Moon Phases

[Madmatx]

When mushroom farming I just looked here and accounted for the day before and after the main 4 phases and have never had a problem.

*** Oh if you click on a day it shows you if it's waxing or waning crescent or gibbous.

[Clip]

I guess I'm mis-remembering it. Here are some illuminating comments from the code. It uses a public-domain bit of code I found (and can't find online anymore, the links are dead...) that "determines the fraction of the moon's disk that is illuminated at a given time", and also tells if the moon is waxing or waning, for a given Julian date. (Presumably at midnight, but I don't really know. The formula uses a bunch of hard-coded constants that only work at the date-level.) It's based on calculations by Jean Meeus, I think this book https://www.amazon.com/Astronomical-.../dp/0943396611. I honestly don't understand any of the moon math.

Using that code, my code just divvies the dates up, assigning a moon phase to each date.


// we want the "full moon" to be EXACTLY 3 days. So we find the
// most full day, and declare that day to be full, as well as the day
// before and after it.
// We do the same for the "new moon" and the two quarter-moons, also exactly 3 days.


// the dates that don't have phases yet are the "leftover" phases.
// Their length varies between 3 and 5 days depending on the month

The "leftover" phases are WaxingCrescentMoon, WaxingGibbousMoon, WaningGibbousMoon, and WaningCrescentMoon.

Is there any chance you'd consider wrapping that in a leap-year-aware date range loop and post the results for the next several years as a text file? Then we have an authoritative, simple answer, and all you have to do is never ever change any code that might affect it ever again, forever? What could go wrong?

[Daguin]

I've updated my Windows app to follow this algorithm more closely. It's still not perfect, unfortunately, by I gave my best shot.

Thanks for continuing support with new versions.

[SausageJavelins]

Thanks for continuing support with new versions.

I will update mine soon as well. Right now box timers are the focus but proper phase calculation is next.

You all can use Niph's app for phase calculation in the meantime!

[alleryn]

This has a chart of the moon phase dates for a hundred years: http://astropixels.com/ephemeris/moo...es2001gmt.html

Then it's +/- 1 day around the full/new/first q/last q, and fill inbetween. Thinking about adding this to the wiki. (Would just need to do the data entry for the dates each month and a bit of #expr (math and syntax)).

Here also is some general info on why the synodic month varies (so why a simple "Seconds elapsed since some fixed time / Period of synodic month" model isn't sufficient): http://astropixels.com/ephemeris/moo...month2001.html

Edit:
Proof of concept at
http://wiki.projectgorgon.com/wiki/U...dbox/MoonPhase
This should chart the PG moon phases for today and the next 3 days, until the next full moon on Oct. 31, 2020.