Percy
FIND @name TRANSIT
(3:3){ OF @body
| ACROSS @body
| FROM @body }
(0:1){ WITHIN @name }
STEP SIZE @number(0:)
The FIND TRANSIT command locates intervals during which the transit OF a
target body ACROSS a second body is visible FROM an observing body.
The left endpoint of each interval represents the beginning of a particular transit; the right endpoint represents the end of the same transit. (Of course, if the search interval begins or ends during a transit, the first or last interval will not contain a complete event.)
Both the transiting and transited bodies are represented by spheres, with radii equal to the longest equatorial radii of the tri-axial ellipsoids used to model the respective bodies.
A transit is defined to begin when the observer would see the limbs of the transiting and transited spheres first touch. The transit ends when the limbs of the two spheres would be observed to end their contact.
In the following example, the FIND TRANSIT command is used to locate
intervals when Io is in transit across Jupiter as seen from Earth. The search
interval is restricted to intervals (determined previously) when Jupiter is
more than 50 degrees from the Sun.
IMPORT JUPITER_50_DEGREES.WIN AS JUP_CLEAR;
FIND IO_TRN TRANSIT OF IO
ACROSS JUPITER
FROM EARTH
WITHIN JUP_CLEAR
STEP SIZE 20 MINUTES;