78:. The differences between these time standards are of the order of a minute, so that for minute accuracy of timings the standard used has to be stated. The HJD correction involves the heliocentric position of the Earth, which is expressed in TT. While the practical choice may be UTC, the natural choice is TT.
47:, the time the event is observed depends on the changing position of the observer in the Solar System. Before multiple observations can be combined, they must be reduced to a common, fixed, reference location. This correction also depends on the direction to the object or event being timed.
59:. Elsewhere, it is approximately an annual sine curve, and the highest amplitude occurs on the ecliptic. The maximum correction corresponds to the time in which light travels the distance from the Sun to the Earth, i.e. ±8.3 min (500 s, 0.0058 days).
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of the Solar System, the HJD correction is not actually to a fixed reference. The difference between correction to the heliocentre and to the barycentre is up to ±4 s. For second accuracy, the
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The common formulation of the HJD correction assumes that the object is at infinite distance, certainly beyond the Solar System. The resulting error for
666:
Eastman, Jason; Siverd, Robert; Gaudi, B. Scott (2010). "Achieving Better Than 1 Minute
Accuracy in the Heliocentric and Barycentric Julian Dates".
195:
104:– which is closer than the Sun – can be wrongly placed on the far side of the Sun, resulting in an error of about 15 min.
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633:{\displaystyle HJD=JD-{\frac {r}{c}}\cdot \cos(\beta )\cdot \cos(\lambda -\lambda _{\odot })}
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Julian Date (JD) corrected for differences in the Earth's position with respect to the Sun
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Sky catalogue 2000.0, volume 2, double stars, variable stars and nonstellar objects
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is the distance between Sun and observer. The same equation can be used with any
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The correction is zero (HJD = JD) for objects at the poles of the
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from the observer toward the object or event, and the speed of light
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259:{\displaystyle HJD=JD+{\frac {{\vec {r}}\cdot {\hat {n}}}{c}}}
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from the heliocentre to the observer, the unit vector
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89:(BJD) should be calculated instead of the HJD.
338:) and of the extrasolar object this becomes:
8:
716:, p. xvii. Sky Publishing Corporation (
504:{\displaystyle HJD=JD-{\frac {r}{c}}\cdot }
39:. When timing events that occur beyond the
62:JD and HJD are defined independent of the
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31:(JD) corrected for differences in the
541:the Sun is at latitude zero, so that
7:
712:A. Hirshfeld, R.W. Sinnott (1997).
745:: Online converter from UTC to BJD
724:) and Cambridge University Press (
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753:to UTC, or HJD (UTC or TT) to BJD
35:'s position with respect to the
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163:{\displaystyle {\hat {n}}}
134:{\displaystyle {\vec {r}}}
51:Magnitude and limitations
21:Heliocentric Julian Date
649:Barycentric Julian Date
311:{\displaystyle \delta }
288:{\displaystyle \alpha }
112:In terms of the vector
87:Barycentric Julian Date
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331:{\displaystyle \odot }
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98:main asteroid belt
776:Time in astronomy
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526:{\displaystyle r}
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183:{\displaystyle c}
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674:(894): 935–946.
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45:speed of light
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41:Solar System
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771:Time scales
297:declination
108:Calculation
29:Julian Date
765:Categories
660:References
83:barycentre
681:1005.4415
623:⊙
619:λ
615:−
612:λ
606:
600:⋅
594:β
588:
582:⋅
569:−
491:⊙
487:α
483:−
480:α
474:
468:⋅
460:⊙
456:δ
449:
443:⋅
437:δ
431:
417:⊙
413:δ
406:
400:⋅
394:δ
388:
379:⋅
366:−
326:⊙
306:δ
283:α
268:When the
245:^
236:⋅
230:→
155:^
126:→
27:) is the
706:54726821
643:See also
68:UTC, UT1
57:ecliptic
686:Bibcode
728:
720:
704:
513:where
749:, BJD
702:S2CID
676:arXiv
537:. In
33:Earth
726:ISBN
718:ISBN
295:and
102:Moon
19:The
755:TDB
751:TDB
747:TDB
694:doi
672:122
603:cos
585:cos
471:cos
446:cos
428:cos
403:sin
385:sin
76:TAI
74:or
37:Sun
25:HJD
767::
732:).
700:.
692:.
684:.
670:.
190::
72:TT
70:,
757:.
708:.
696::
688::
678::
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609:(
597:)
591:(
577:c
574:r
566:D
563:J
560:=
557:D
554:J
551:H
521:r
499:]
496:)
477:(
465:)
452:(
440:)
434:(
425:+
422:)
409:(
397:)
391:(
382:[
374:c
371:r
363:D
360:J
357:=
354:D
351:J
348:H
252:c
242:n
227:r
218:+
215:D
212:J
209:=
206:D
203:J
200:H
178:c
152:n
123:r
23:(
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