View Full Version : Harvest Moon

2010-Sep-21, 08:27 PM
Over the next few nights weíll be witnessing the annual Harvest Moon. Thatís whatís seen when a Full Moon occurs near the time of the Autumnal Equinox. This month geocentrically the Full Moon will appear most completely illuminated on September 23 at 09:09 UT. The Autumnal Equinox will be reached six hours earlier at 3:09 UT, which is an unusually small difference. Brilliant Jupiter will appear in the vicinity of the Harvest Moon.

The notable aspect of the Harvest Moon is that for several evenings the nearly Full Moon rises near sunset and not long after the time of the previous rising, allowing farmers extra moonlight to complete the harvest. On average the Moon rises 50.47 minutes later each day, but here in Chicagoland that will be only about 22 minutes over the next few evenings. Thatís due to the sharp inclination the ecliptic has with the eastern horizon at dusk during this time of year. The Harvest Moon occurring near apogee this year adds to the effect since that retards its daily advance in ecliptical longitude. The drawback is that that makes it appear smaller than normal.

On my website is a chart illustrating the variances among upcoming Full Moons. Click http://www.curtrenz.com/astronomical then go to the page for The Moon and click the link to Full Moons.

2010-Sep-21, 10:54 PM
Fantastic write up! I love how you pack tons of great info in such simple paragraphs.

2010-Sep-22, 02:03 AM
It looked very pretty this evening, particularly with Jupiter trailing it. I suspect in a couple of days the Moon and Jupiter will make a very nice pair in the sky.

2010-Sep-22, 09:25 PM
Come and gone. The Moon is always good to look at. I think being at apogee did it a favour because it diminished its apparent magnitude therefore making it easier to appreciate its acne.

It only serves as a reminder that it's been a whole two weeks since Eid, which means harvest time for owners of gyms in areas with a large Muslim community. An intern on our team said he always puts on weight at Ramadan (although in his case, put on weight is a relative term).

2010-Sep-23, 10:36 AM
Thank you Mr Renz!

Have a lovely Autumn too!

thoth II
2010-Oct-11, 03:57 PM
http://www.palmbeachstate.edu/faculty/sundquij/ast1002/harvest moon.bmpThat diagram shows in USA the eastern horizon, the ecliptic for harvest moon at moonrise, and the comparison ecliptic at solstice , which is at a higher angle than at equinox by 23 degrees higher

It is easy to see above features by looking at a 3-D celestial sphere if you have one. You'll see that only at equinoxes does the celestial equator intersect the ecliptic, and at 23 degrees. At the solstices, (I've pictured only the winter), the ecliptic is parallel to the celestial equator and displaced from it by 23 degrees.

I have not pictured above the other possibility for the equinox, there it would be 23 degrees above, not below, the celestial equator, but above is for moonrise at harvest moon.