Clocks, Calendars, Coordinates, Orbits (2024). 4 Classes.
Reduced tuition of $50/$60(non-members)
Wednesdays, 7 PM. June 12, 19, 26; July 10 (new date)
The measurements of time by clocks and calendars has roots in astronomy. Historically, calendar dates were complex to fix in all cultures because the Earth, moon, and sun have revolution rates that are not simple multiples of one another. Objects in the sky and in space are assigned coordinates using different systems. These coordinates are vital to determining and specifying the exact positions, motions, and orbits of space objects. It takes six parameters to specify an orbit. We explore these themes.
June 12- Measuring time
Solar vs. sidereal day. Defining 1 second. Modern timekeeping. Leap seconds. Time zones. Sundials, analemma.
June 19- Calendars
Constraints of rotation and revolution. Solar, sidereal, lunar, lunisolar calendars. Ancient Roman, Julian, Gregorian calendars. Rules for leap years. Passover and Easter. Julian Dates. Review of moon phases essential to lunar calendars. Jewish, Muslim, Chinese, Mayan calendars. Non-astronomical calendars. Colonial American documents had two dates on them because following England we couldn’t decide which system to go with.
June 26- Coordinate systems and mapping the heavens
Local coordinates: altitude, azimuth. Review of latitude & longitude on Earth. Celestial coordinates: declination, right ascension. Algorithms for converting, ALTI/AZIMUTH ––>DEC/RA. Many variables, spherical trigonometry, exact UTC time.
Correcting for precession, by 50-year EPOCHS in star maps and by hourly computer updates in professional telescopes.
2-D map issues, sky projections. Ecliptic and Galactic coordinates.
Review of celestial sphere and constellations. 88 official list, hundreds of asterisms. Rey diagrams. Circumpolar and Zodiac constellations. Usefulness for mapping, locating objects, star guides.
Naming stars: proper, Bayer, Flamsteed. Star maps, star globes, star catalogs.
July 10 (new date) – Orbital parameters
Kepler’s laws. Ellipses. The six key orbital parameters. What must be measured to define an orbit, and how frequently? Newton’s geometric procedures. Liebnizt and Euler procedures. Modern procedures- “MIT telegram”, high speed computers. Technical printout of parameters. Converting back to DEC/RA and Alti/Azimuth coordinates. Overview of the math and software needed for defining orbits.
INSTRUCTOR- David Kiefer. Astronomy teacher, Brooklyn College. Chairman of the AAA Classes Committee, and Board member.
