Need help on moon times

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veritta

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Hello everyone! I'm new to the message board. I just signed up for astronomy in university, I think its fascinating but I have no background so I need help with really simple questions. <br /><br />Could you please explain to me how you would figure out the following problem? (i'm in Hamilton, close to Toronto)<br /><br />At what local time of day or night is the Moon "overhead" (that is, as high in the sky as it will get, when it transits) 10-11 days after it was "new"? Give your time to the nearest full hour, and use "military" time so that you need not specify "am" or "pm"; thus if the answer is 5 pm you enter 1700.<br /><br />When does the Moon of the previous question set? Again, give your answer in military time, so a time such as "7 am" is written as 700.<br /><br />I'm not even sure of how to approach this...
 
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Saiph

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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>
 
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Saiph

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oops, forgot to post a useful picture: <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>
 
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Saiph

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well...that wasn't as big as I thought...<br /><br />lets try this one: <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>
 
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veritta

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Hmm okay so let's see if I get this straight. 11 days after the new moon, we would have a waxing gibbous. This means that its diagnoal left from the earth on the diagram with the rays coming in from the right. If we think of noon as a parallel with new on the same line is full, waking gibbous is above full so it would be at its highest point at 9 p.m. according to the diagram... so at 9 on the diagram it is directly overhead. So in order to figure out when it sets, wehave to think of 9 as the midway between a 12 hour ranfge, so it would set at 3 in the morning....<br /><br />does that make sense? or am i going insane?
 
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Saiph

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looks good to me <img src="/images/icons/smile.gif" /><br /><br />and I used to be TA for such a class. <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>
 
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