stellar_phenomena: Julian day for star's appearance or disappearance
In Susarro/arqastwb: Archaeoastronomy algorithms

Description Usage Arguments Value Examples

Julian day for star's appearance or disappearance

stellar_phenomena(from, to, star_name, geographic_latitude,
  geographic_longitude, geographic_altitude, horizontal_coordinate,
  horizontal_star_time, coordinate_threshold,
  visibility_type = "appearance", silent = FALSE)

`from`	Initial value of the interval to be searched
`to`	Final value of the interval to be searched
`star_name`	Name of the star
`geographic_latitude`	Geographical latitude in degrees
`geographic_longitude`	Geographical longitude in degrees
`geographic_altitude`	Geographical altitude in meters
`horizontal_coordinate`	Horizontal coordinate (azimuth or elevation) to compare to a reference coordinate value or threshold
`horizontal_star_time`	"setting" or "rising". Only required if horizontal_coordinate=="elevation"
`coordinate_threshold`	Horizontal coordinate value used as a reference or threshold for the specified horizonal coordinate of the star during its setting or rising
`visibility_type`	"appearance" (visual magnitude of the sky increasing as days go by) or "disappearance" (visual magnitude of the sky decreasing as days go by)
`silent`	If false a text progress bar is shown

Time of the star's appearance or disappearance during its setting or rising at twilight time

years<--2000:-1999
from<-str2jd(paste(years[1],"01","01",sep="-"))
to<-str2jd(paste(years[length(years)],"01","01",sep="-"))
star_name<-"epsilon orionis"
stellar_phenomena(from=from,to=to, star_name=star_name,
                  geographic_latitude=str2degrees("42\u00b036'25\u0022N"),
                  geographic_longitude=str2degrees("5\u00b033'58\u0022W"),
                  geographic_altitude=782,
                  horizontal_coordinate="elevation", horizontal_star_time="setting",
                  coordinate_threshold=2, visibility_type="disappearance", silent=FALSE)