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Moon in the East Calculations

Viewing Conditions

The Moon has to meet three conditions so someone in Kansas City can see it in the eastern, daytime, morning sky.

Eastern Sky: Only times before Moon transit count because after that, the Moon is west. Note: Moon transit is a concept similar to "Sun noon" or "local noon". It's the time of that the Moon is at its highest point above an observer's horizon.

Daytime: Only times after sunrise count because we're defining daytime as "after sunrise".

Morning: Only times also before sun transit (noon) count because after that, it isn't morning any more.

Procedure

The times (MoonTime) the Moon will be visible, then, is MoonTime = UpperTime - LowerTime, where we pick the upper and lower times so they satisfy the viewing conditions.

That means the LowerTime has to be greater or equal to the time of sunrise so the Moon is visible in the daylight. It also has to be greater or equal to the Moon rise so the Moon will be up.

The UpperTime is a little more tricky. The UpperTime must be less than or equal to12 so the Moon is visible in the morning. The UpperTime must also be less than or equal to the Moon transit time so the Moon will be in the East sky. Also Moon transit time must be greater than or equal to sunrise so the Moon is in the East during the daytime.

We go to the US Naval Observatory website to get data for Kansas City during June 2001--corrected to Daylight Saving Time. We examine the sunrises, Moon rises, and Moon transit times and pick out those days that satisfy the viewing conditions for at least a few minutes during the day. We end up with the 15 days from the 12^th through the 26^th as feasible days.

For days 12 - 20, Moon transit occurs before noon so its morning and, to keep the Moon in the East, we use UpperTime = MoonTransit. Also Moon rise always occurs before sunrise. So, to make sure we see the Moon during the day, we set LowerTime = SunRise. That makes, MoonTime = MoonTransit - SunRise.

For days 21 - 26, Moon transit occurs after noon. So, to keep the times in the morning, we set UpperTime = 12. Also, the Moon rises after sunrise. So, to only include times when the Moon is up, we set LowerTime = MoonRise. That makes MoonTime = 12 - MoonRise.

We end up with the following table of times (Central Daylight Time):

Discussion

We have determined that we can theoretically see the Moon in Kansas City in the morning, daytime, Eastern sky for the days and the times (Moon times) given in the table above.

Now, let's consider when it's practical to see the Moon. What days should we throw out? The New Moon occurs on the 21^st and that's when you can't see the dark Moon at all, or at least it's extremely difficult to see it. So throw out a couple of days around each side of the 21^st, when daytime viewing is difficult to impossible. We eliminate days: 19^th, 20^th, 21^st, 22^nd, and 23^rd. Now we have only 10 viewing days.

We use this table to arrive at the short viewing times. On the 12^th and 26^th we can see the Moon in the morning, Eastern, daylight sky of Kansas City for only 30 and 16 minutes. Driving to work, you probably wouldn't spot the Moon with such small windows of opportunity. So we'll throw those days out, too. That leaves eight days when you can see the Moon in the eastern sky for at least an hour in the morning: 13^th through 18^th and the 24^th and 25^th.

Between the 14^th and the 18^th probably are your best chances. The 14^th is the Third Quarter Moon so you're looking for a big half Moon, which is visible in the morning eastern sky for about three hours.

In the morning from the 15^th on, the waning Moon hangs in the east for increasing times until the 18^th when you can see the sliver, crescent Moon for almost five hours. You can see the Moon for increasing times from the 15^th to 18^th because sunrise stays the same (5:52 a.m.) but the time when the Moon "stops being in the east" (i.e., the transit time) gets later and later as the Moon moves through its orbit, rising farther and farther North each day.

These approximate times apply just to Kansas City, a central U.S. city. The method of calculation is similar and the general trends should be valid, though, in most mid-latitude locations with possibly some corrections for longitude.