- #1
fizzy
- 193
- 17
JD is a count of days since an arbitrary zero datum, in order to have a non variable timescale for astronomical calculations and ephemeris software.
Since these are real noon-to-noon days they must actually be variable in length due to variations in LOD over time. WonkyPedia tells us that it has changed around 70s in the last century.
So , how long is a JD? Does it vary with time? How do I compare or convert to some other observable time period like sidereal or tropical year?
Thanks.
Since these are real noon-to-noon days they must actually be variable in length due to variations in LOD over time. WonkyPedia tells us that it has changed around 70s in the last century.
So , how long is a JD? Does it vary with time? How do I compare or convert to some other observable time period like sidereal or tropical year?
Thanks.