|Posted by: LowerCal, 8:36 PM GMT on August 20, 2010||+4|
One effect of equinoctial periods is the temporary disruption of communications satellites. For all geostationary satellites, there are a few days near the equinox when the sun goes directly behind the satellite relative to Earth (ie, within the beamwidth of the groundstation antenna) for a short period each day. The Sun's immense power and broad radiation spectrum overload the Earth station's reception circuits with noise and, depending on antenna size and other factors, temporarily disrupt or degrade the circuit. The duration of those effects varies but can range from a few minutes to an hour. (For a given frequency band, a larger antenna has a narrower beamwidth, hence experience shorter duration "Sun outage" windows).Cultural Aspects of the Equinox
In general, the moon rises about 50 minutes later each day, as it moves in orbit around Earth. All full moons rise around the time of sunset. The Harvest Moon and Hunter's Moon are special because—as seen from the northern hemisphere—the time of moonrise on successive evenings is shorter than usual. The moon rises approximately 30 minutes later, from one night to the next, as seen from about 40 degrees N. latitude, for several evenings around the full Hunter's or Harvest Moons.
Thus there is no long period of darkness between sunset and moonrise, around the time of these full moons. In times past, this feature of these autumn moons was said to help hunters tracking their prey (or, in the case of the Harvest Moon, farmers working in the fields). They could continue tracking their prey (or bringing in their crops) by moonlight even when the sun had gone down. Hence the name Hunter's (or Harvest) Moon.
The reason for the shorter-than-usual rising time between successive moonrises around the time of the Harvest and Hunter's Moon is that the orbit of the Moon makes a narrow angle with respect to the horizon in the evening in autumn, leading the Moon to higher positions in the sky each successive day.
|Updated: 7:20 PM GMT on September 21, 2010||Permalink | A A A|
Astronomy with a minimum of terminology and technology.
Tropical Weather Stickers®
APRSWXNET Woodland Hills CA US
|Dew Point:||49.0 °F|
|Wind:||5.0 mph from the SE|
|Wind Gust:||11.0 mph|
Updated: 9:03 AM PDT on May 23, 2013
At Gonzales Drive
Woodland Hills, CA
|Dew Point:||49.9 °F|
|Wind Gust:||7.0 mph|
Updated: 9:47 AM PDT on May 23, 2013