Minor Lunar Standstill
Halfway between one Major Lunar Standstill and the next (every 18.6 years), the moon reaches Minor Lunar Standstill where the monthly range of moonrise/set to the north and south is at a minimum, and does not reach the range that the sun reaches at solstices. During Major Lunar Standstill eclipses occur near Equinoxes. The next Minor Lunar Standstill will occur in 2034.
Possible Major Sites for Initial Documentation:
Newgrange (intervisibility with Knowth and Dowth)
Parc y Meirw (along the stone row in the direction of setting)
The last Minor Lunar Standstill was in 2015 and the next is in 2034, but there is no need to wait for 18.6 years to make real-time observations at sites with suspected/proposed minor lunar standstill alignments. Because the minor standstill positions are within the range of the sun each year, there are two opportunities to use the sun as a proxy for minor lunar standstill positions every year as the sun moves between solstice maximums/minimums. On these dates the rising and setting sun will match the position of the rising and setting moon during minor lunar standstill. Using the sun as a proxy for the position of the moon during minor lunar standstill can occur twice each year for northern and southern positions by calculating solar declination values that match lunar declination values for a given latitude by adjusting for lunar parallax. Below is a PDF document with these calculations for different periods of time for a range of latitudes (and a sample screenshot for 3000 BC values). These dates should apply to any year within about 1 day. Making observations for a few days on either side can be very useful for comparison or to help pinpoint the best date and corresponding declination which can be matched to a date range.
Possible Major Sites for Initial Documentation:
Newgrange (intervisibility with Knowth and Dowth)
Parc y Meirw (along the stone row in the direction of setting)
The last Minor Lunar Standstill was in 2015 and the next is in 2034, but there is no need to wait for 18.6 years to make real-time observations at sites with suspected/proposed minor lunar standstill alignments. Because the minor standstill positions are within the range of the sun each year, there are two opportunities to use the sun as a proxy for minor lunar standstill positions every year as the sun moves between solstice maximums/minimums. On these dates the rising and setting sun will match the position of the rising and setting moon during minor lunar standstill. Using the sun as a proxy for the position of the moon during minor lunar standstill can occur twice each year for northern and southern positions by calculating solar declination values that match lunar declination values for a given latitude by adjusting for lunar parallax. Below is a PDF document with these calculations for different periods of time for a range of latitudes (and a sample screenshot for 3000 BC values). These dates should apply to any year within about 1 day. Making observations for a few days on either side can be very useful for comparison or to help pinpoint the best date and corresponding declination which can be matched to a date range.
| solar_proxies_for_minor_lunar_standstills.pdf |
