Octagon Moonrise.Org

F.A.Q. Focus


Why aren't we celebrating the northernmost rising of the moon on the precise date of this singular astronomical event?


In each lunar month, the moon goes through a cycle that includes monthly maximum northern and maximum southern moonrises and corresponding monthly maximum northern and southern moonsets.  In some months, the angle separating those maximal points is only 49 degrees.  This angle defines the absolute minimum northern and minimum southern moonrises.  During months when the angle reaches 77 degrees, the moon is seen to rise at its maximum northern and maximum southern positions.  These are the maximum azimuth points for that month, but they also represent the absolute maximum azimuths for the entire cycle.  The actual absolute maximum northern azimuth is reached only once in the 18.6-year cycle, but in the monthly cycles before and after that event the monthly maximum northern moonrise approaches the azimuth of the absolute maximum northern moonrise.


The actual (singular) event when the moon rises at its northernmost azimuth, which occurs once every 18.6 years, will occur on 15 September 2006 at 12:08 AM.  Unfortunately, on that date it will be less than a quarter moon and will, therefore, not be an impressive visual display.  Also, Thursday is a school night and the timing is such that many young children may be unable stay up for the event.


The November 2005 alignment will be within two degrees of the maximum northern moonrise, and it will be slightly more than 90% full.  The October alignment will be nearly 70% full, even closer to the northernmost alignment, and will take place at 10:13 on a Saturday evening.  The September moonrise also will occur on a Saturday night, but it will be just a quarter moon.  Since the 2005 moonrises will occur earlier in the evening on weekends, they will be accessible to a wider and more diverse audience, including children who will not have to get up early for school the next day.  Because the November, October, and September 2005 events will be more visually impressive and more accessible to a wider audience, and because these moonrises will be virtually indistinguishable from the actual northernmost rising of the moon to most observers, these have been selected as our observance dates for a celebration of the northernmost rising of the moon at Octagon Earthworks, Newark Earthworks State Memorial.


The celebration need not be limited to these three days.  In fact, the likelihood that Ohio’s skies will be clear on any given day in Ohio's autumn is unfortunately low.  Dr. Michael Mickelson provided the following list of alternative dates using data from NASA’s Jet Propulsion Laboratory Web Ephemeris Generator (http://ssd.jpl.nasa.gov/cgi-bin/ehp).  The list includes six dates in 2005 and 2006 when the rising of the moon most closely approaches the absolute maximum northern azimuth.   There is a special significance to the event on September 14th, 2006, but each of the dates is an opportunity to celebrate the achievements of Ohio's ancient Native American peoples. 



Newark Octagon  Latitude 40 03’ 10”              Longitude 82 26’ 50”

Table prepared using the JPL Horizons Ephemeris Generator at http://ssd.jpl.nasa.gov/horizons.html and compared with output from Naval Observatory’s Multiyear Interactive Computer Almanac, MICA 2.0-beta.

Year Month Day Time$ Azimuth Illumination
2005 September 24 Saturday   11:29 PM EDT 51.54 50.9%
2005 October     22 Saturday 10:13 PM EDT 51.79 68.0%
2005 November 18 Friday   7:00 PM EST 51.63 90.3%
2006 September 15 Friday* 12:08 AM EDT 51.25 42.2%
2006 October      11 Wednesday   9:59 PM EDT 51.52 69.3%
2006 November   8 Wednesday   7:43 PM EST 51.68 84.1%

$ Note that Eastern Daylight Savings Time is denoted by EDT = EST+1 hour.
Note that this time is 8 minutes after the midnight of Thursday evening September 14th , thus occurring  early in the morning of September 15th at 12:08 AM.



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