start with what you know:<br /><br />You're starting point is the "new" moon.<br /><br />What time of day is the "new" moon directly overhead (or "as high as it gets")?<br /><br />To figure that out, think of where the moon is in relation to the earth, and the sun. On the new moon, we see only the shadowed side of the moon, meaning that it must be between us an the sun (or very close). A full moon is when the moon is on the opposite side of the earth from the sun.<br /><br />So, when is the sun straight overhead? Noon, and so is the new moon.<br /><br />Now, how much earlier, or later, does the moon rise each day? (you look that up). Add (or subtract) 10x that many hours from noon to find when that phase of the moon is "overhead".<br /><br />To figure out when that phase rises or sets, think of this: The moon is up a total of 12 hours. When it is straight overhead, it's halfway through it's trip. So how long until it sets? how long ago did it rise? That will tell you how many hours to add or subtract from the "straight overhead" time. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>