The Moon in the Sky

.....In response to a couple of questions, I've tried to come up with a device that would help one work out when the Moon will rise and set, and what part of the sky it will be in for any given time of day. This is my result. First, start with the base of this ("Lunalabe"? ""? I need a better name for it), a wheel that another, smaller wheel will move in.

.....Once that is done, find a way to attach this smaller wheel so that the two wheels have a

common center. The way that I first did this was to use a paper clip; an alternative would be to go to a craft/scrapbooking store and buy a specialty brad which can attach through the center. Perhaps it would be better to use an eyelet, or something that has less of a chance of ripping - we're really at the end of my know-how on this subject, but you can check out my crude attempt in the photograph below.

.....Here is how this works, if you know the phase of the Moon, or when the new and/or full moon is that month (you can find these on many calendars, plus, I will now begin posting that information at the beginning of each month. For August, 2010:

Last Quarter: August 2

New Moon: August 9
First Quarter: August 16

Full Moon: August 24

The lunar month is 29.5 days long. This means that the time between phases is roughly one week, which we can use to find the Moon between these dates. Consider this Friday, August 20th. This is midway between First Quarter and the Full Moon, so we start by looking on the wheel between the First Quarter and the Full Moon. The Moon between the New Moon and the Full Moon is waxing (increasing), and the Moon between First Quarter and Last Quarter is gibbous, so the phase of the Moon on Friday will be "waxing gibbous". This has a "+9" by it, which means that the Moon (all else being equal) will rise, set, everything, nine hours after the Sun does. If we take as an average that the Sun rises at 6 AM, gets as high in the sky as it is going to get (transits) at noon, and sets at 6 PM, this indicates that on Friday, we should expect the Moon to rise at 3 PM, transit at 9 PM, and set at 3 AM.

.....This is where we also have to look at the outer wheel. Line up the lines representing the direction of the Sun (the wheel works because as far as the Earth and the Moon are concerned, the Sun is so far away that it is not a point to examine in perspective, but a direction) is coming from "August". (This also shows that in late August the Sun is in front of the stars of the constellation of Leo.) Imagining a line from the center of the wheel out to the constellation ring, the Moon on August 20th should be in front of the stars of Sagittarius. Sagittarius has a "-2" next to it, because Sagittarius is far to the south, and so this constellation is not above the horizon as long as the others. (The Sun is in Sagittarius in December and January, and the Sun is not above the horizon as long as it is in later months.) The "-2" means that in this constellation there will be two hours less time above the horizon at rising and setting, so we expect to Moon on Friday to rise at 5 PM, transit at 9 PM (this does not change), and set at 1 AM. If we compare this to the actual times, the Moon will rise at 6:01 PM, transit at 10:30, and set at 3:03. This seems wrong, if you don't take that hated Daylight Savings Time into account.

.....Tell you what, during DST, just shift your predition forward one hour, so our expected times are Moon rise at 6 PM (pretty close), transit at 10 PM (close-ish, I make no promises to be exact), and Moon set at 2 AM (admittedly sketchy - I might need more work on the hour modifiers on the outer wheel). Still though, this first version does provide a decent rough time, and it identifies where the Moon will be in the sky well. You can use this to help learn the constellations along the path of the Sun and Moonin the sky (the zodiac), as long as the Moon is not too bright.

.....On the other hand, if you see the Moon in the sky and you recognize its phase,this can be used to find rise/set times from that as well. This (I certainly hope) will help you find the Moon in the sky, and this will tell you what constellation it is in.

.....Please let me know if there is a feature that you would like the wheel to do that you do not think that it does, or if there is a feature that is too distracting. If you would like to try this, I have the images as two pages in a PowerPoint presentation at this site.

.....SPECIAL NOTE FOR TEACHERS. I use this device in class to try to illustrate the relationship between the Earth, Moon and Sun defines the appearance of the Moon. If you would be interested in something like this, please let me know, and we can compare notes.