Editing Julian Day

Semimajor and semiminor axes

The '''Semimajor axis''' of an orbit is defined as one-half of the long axis of an ellipse or an elliptical orbit, a measure of the size of the orbit.

In an elliptical orbit, the major axis passes through both foci, the central body being at or near one foci. There is nothing at the other foci. The distance between the highest point along the orbit to the barycenter is the apoapsis, the low point is the periapsis. The semimajor axis is one half the sum of the apoapsis and the periapsis.
@@ Line 1: / Line 1: @@
-'''Julian day''' is a count of days since the beginning of the Julian period, used  to calculating days between any two events.
+Semimajor and semiminor axes
-The calendar, with twelve months of the year, each with varying number of days, and February with 28 or twenty nine days in leap years, makes it difficult and complicated to calculate the time between any two events. Joseph Scaliger proposed that a Julian Period be used to time events, beginning at a time sufficiently far in the past as to precede dates in recorded history. The Julian period begins Monday, 1 January 4713 B.C. and is 86400 seconds of time. The Julian Year is 365.25 days and the Julian century is 36525 days.
+The '''Semimajor axis''' of an orbit is defined as one-half of the long axis of an ellipse or an elliptical orbit, a measure of the size of the orbit.
-'''Julian Day''' counts the number of days from the beginning of the Julian period allowing the calculating of event times. '''Julian Day Number''' is an integer number assigned to any one day, the JD beginning at noon. The '''Julian Date''' is an instant given as a decimal part of the day since the previous noon.
+In an elliptical orbit, the major axis passes through both foci, the central body being at or near one foci. There is nothing at the other foci. The distance between the highest point along the orbit to the barycenter is the apoapsis, the low point is the periapsis. The semimajor axis is one half the sum of the apoapsis and the periapsis.
-The '''Modified Julian Date''' is the number of days (and fractional days) elapsed since midnight GMT on 17 November 1858. This is 2400000.5 smaller than the standard Julian Date.
-In Orbiter it is used to define the current time in scenario files; it is also displayed in the [[heads up display|HUD]].
-== Calculations ==
-'''To convert a Gregorian calendar date to Julian Day Number, used for dates on or after 15 October 1582 for Catholic countries, other countries changed on other dates):'''
-JDN = (1461 × (Y + 4800 + (M − 14)/12))/4 +(367 × (M − 2 − 12 × ((M − 14)/12)))/12 − (3 × ((Y + 4900 + (M - 14)/12)/100))/4 + D − 32075<ref name="WikiJD">[[w:Julian Day|Julian Day at Wikipedia]]</ref>
-where
-*Y = year
-*M = month (1-12)
-*D = day of month (1-31)
-'''To convert a Julian calendar date to Julian Day Number, used for dates on or before 4 October 1582 for Catholic countries, other countries changed on other dates):'''
-JDN = 367 × Y − (7 × (Y + 5001 + (M − 9)/7))/4 + (275 × M)/9 + D + 1729777<ref name="WikiJD"/>
-where
-*Y = year
-*M = month (1-12)
-*D = day of month (1-31)
-'''To convert Julian Day Number to Julian Date, given time of day:'''
-JD = JDN + (h - 12)/24 + m/1440 + s/86400<ref name="WikiJD"/>
-where
-*h = hour
-*m = minute
-*s = second
-'''To convert Julian Date to Modified Julian Date as used by Orbiter:'''
-MJD is used since the beginning of the space program, eliminates the initial '24' from the number and begins the Date at midnight.
-MJD = JD - 2400000.5<ref name="WikiJD"/>
-== references ==
-<references/>
-[[Category: Articles]]
-[[Category: Glossary]]