J2000.0 - Factbites

J2000.0 - Factbites
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Topic: J2000.0

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	B1950.0 - Wikipedia, the free encyclopedia
		For comparison to modern J2000.0 positions, the old ones have to be corrected for precession and nutation.
		This standard was superseded by the succeeding epoch, which is currently in standard use, the J2000.0 epoch.
		The "B" in the prefix indicates that it is a Besselian epoch, as opposed to a Julian epoch.
	en.wikipedia.org /wiki/B1950.0 (167 words)

	J2000.0
		J2000.0 entspricht der Festlegung des Fundamentalsystems für den 1.
		Mit J2000.0 wird die derzeit gültige Standard-Epoche der Astronomie bezeichnet, auf die sich alle Himmelskoordinaten von Sternen und der meisten anderen Himmelkörper beziehen.
		Die Definition solcher "Epochen" ist notwendig, weil sich das Bezugssystem der zälestischen Koordinaten durch die Präzession und andere Effekte langsam dreht.
	www.toonorama.com /encyclopedia/J/J2000.0 (195 words)

	Year - Wikipedia, the free encyclopedia
		The draconitic year, eclipse year or ecliptic year is the time for the Sun (as seen from the Earth) to complete one revolution with respect to the same lunar node (a point where the Moon's orbit intersects the ecliptic).
		A heliacal year is the interval between the heliacal risings of a star.
		This term is sometimes also used to designate the time it takes for a complete revolution of the Moon's ascending node around the ecliptic: 18.612 815 932 years (6798.331 019 days).
	en.wikipedia.org /wiki/Year (1668 words)

	ccsystems
		B1950.0 or J2000.0, and epoch is the Besselian epoch, the Julian epoch, or the Julian date of the observation.
		J2000.0, j2000.0, 2000.0, fk5, fk5 J2000, and fk5 2000.0 all specify the mean place post-IAU 1976 or FK5 system.
		J2000.0 or 2000.0, or the equatorial mean place pre-IAU 1976 system (FK4) if equinox is a Besselian epoch, e.g.
	stsdas.stsci.edu /cgi-bin/gethelp.cgi?ccsystems.hlp (1031 words)

	Example Problems
		Compute a set of geocentric position and velocity elements referred to the standard equinox of J2000.0 given the classical elements for an earth satellite on a highly eccentric orbit.
		Compute a set of geocentric position and velocity elements referred to the standard equinox of J2000.0 given the classical elements for a space probe on a hyperbolic escape trajectory.
		Compute a set of geocentric position and velocity elements referred to the standard equinox of J2000.0 given the classical elements for a space probe having parabolic escape velocity.
	www.tamuk.edu /math/scott/stars/probs2.htm (849 words)

	ephem_Gehrels_2.4
		and dec. - j2000.0 = geocentric right ascension and declination referred to the mean equator and equinox of j2000.0.
		= variation by one hour of position of object, translated into variations in right ascension and declination, referred to the mean equator and equinox of j2000.0.
	www.fisica.edu.uy /~gonzalo/ephem_Gehrels_2.4 (487 words)

	N O V A S
		Discussion: This subroutine takes Hipparcos catalog data, which is given for epoch J1991.25, and transforms it to epoch J2000.0 for use in NOVAS subroutines such as APSTAR.
		The vectors computed by SOLSYS are in the equatorial rectangular coordinate system which is oriented to the mean equator and equinox of standard epoch J2000.0.
		The errors of the output data from this version of SOLSYS will increase gradually outside of the four-century span, centered on J2000.0, for which it was optimized.
	aa.usno.navy.mil /software/novas/novas_f/novasf.html (7047 words)

	IRS.TXT
		They are also given for equinox and epoch J2000.0 on the system of FK5 (bytes 151-159 and 172-180) after transformation of the B1950.0 values.
		The data for the 36,027 stars of the IRS were compiled on B1950.0 FK4 and then transformed to J2000.0 FK5.
		The IRS is an all-sky catalog of positions and proper motions that is based on the AGK3R in the northern hemisphere and on the newly completed SRS in the south.
	ad.usno.navy.mil /star/IRS/IRS.TXT (2018 words)

	Év - Wikipédia
		365.259635864 nap (365nap 6h 13m 52s) (J2000.0 epochára).
		365.24218967 nap (365nap 5h 48m 45s) (J2000.0 epochára).
		365.256363051 nap (365nap 6h 9m 9s) (J2000.0 epochára = 2000.
	hu.wikipedia.org /wiki/%C3%89v (344 words)

	Astrographic Catalogue Reference Stars
		The data included are catalog part, ACRS number, equatorial coordinates (equinox, equator, epoch B1950.0 and J2000.0), proper motions (B1950.0 and J2000.0), original epochs, weights for right ascension and declination, and reference data such as DM numbers (BD, CD, CPD), AGK3 and CPC2 designations, and an IAU recommended ACRS identifier (based on coordinates).
		The J2000 positions are given for equinox and epoch J2000.0 on the system of FK5 after transformation of the B1950.0 values.
		The ACRS is an all-sky catalog of positions and proper motions that is based on the AGK3 in the north and on the newly completed second Cape Photographic Catalogue (CPC2, de Vegt et al.
	www.cs.wisc.edu /niagara/data/nasa/1171.xml (602 words)

	year
		365.256363051 days (at the epoch J2000.0 = January 1 2000 12:00 TT).
		365.24218967 days (365d 5h 48m 45s) (at the epoch J2000.0).
		The sidereal year is the time for the Earth to complete one revolution of its orbit, as measured in a fixed frame of reference (such as the fixed stars, Latin sidus).
	www.yourencyclopedia.net /Year.html (1019 words)

	INTERNATIONAL CELESTIAL REFERENCE FRAME
		One can estimate that the pole at J2000.0 is shifted from the ICRS pole by 17.1 mas in the direction 12h and by 5.1 mas in the direction 18h.
		The VLBI analysis which permits to calculate radio source coordinates also provide corrections to the conventional IAU models for precession and nutation, thus leading to the accurate estimation of the shift of the mean pole at J2000.0 relative to its conventional position, to which the pole of ICRS is attached.
		Assuming that the error in the precession rate is absorbed by the proper motions of stars, the uncertainty in the FK5 pole position relative to the mean pole at J2000.0 can be estimated to ± 50 mas.
	hpiers.obspm.fr /webiers/results/icrf/Icrs.html (334 words)

	Sidereal time formulas and spreadsheet to navigation accuracy
		This formula is a very basic linear approximation that is good for 50 years either side of J2000.0 dp is the change in the ecliptic longitude of a star due to the nutation, and de is the shift in angle between the ecliptic and equator.
		Finding the days since J2000.0 ------------------------------ All the formulas connecting UT with sidereal time depend on the time elapsed from the fundamental epoch.
		GMST = 280.46061837 + 360.98564736629 * d where d = UT days since J2000.0, including parts of a day You must subtract multiples of 360 to bring the answer into the range 0 to 360 degrees.
	www2.arnes.si /~gljsentvid10/sidereal.htm (1288 words)

	telescope_system_commands2
		J2000.0, J1975, J1988.6 etc. If you omit the B or J prefix the system will assume a sensible default (see §2.1.4); however it is desirable to use this convention because it is a universally accepted means of avoiding any confusion of which epoch or coordinate system is meant.
		The transformation from B1950.0 to J2000.0 and (from J2000.0 to B1950.0) is given in "recipe" form in section B of the Astronomical Almanac and discussed in detail in:
		In this case the display variables J2000_RA and J2000_Dec may be useful; these give the tracking position of the telescope in the J2000.0 FK5 mean coordinate system at the current epoch i.e.
	msowww.anu.edu.au /observing/tcs_manual/celestial_coordinates.html (2981 words)

	Precessing positions from B1950 to J2000
		J2000.0 - the equinox and mean equator of 2000 Jan 1st 12:00 UT
		If you have an observing guide or comet ephemeris in B1950.0 coordinates, and you want to plot the positions of the object on a J2000.0 star atlas, you must correct the B1950 coordinates to J2000.0 by calculating the effects of precession.
		This page provides details of a method for precessing the coordinates of objects from the B1950.0 epoch to the now standard J2000.0 epoch, ignoring the proper motion of the stars.
	www.stargazing.net /Kepler/b1950.html (2559 words)

	Format For Optical Astrometric Observations Of Comets, Minor Planets and Natural Satellites
		For those observations reduced in the J2000.0 system this column is used to indicate how the observation was made.
		For those observations which have been converted to the J2000.0 system by rotating B1950.0 coordinates this column contains `A', to indicate that the value has been adjusted.
		The layout is identical to the old system, except that there is now the option of recording the right ascension to 0.001s, where such precision is justified.
	cfa-www.harvard.edu /iau/info/OpticalObs.html (1354 words)

	Common Amateur Astronomy Terms
		Currently the standard epoch is known as J2000.0.
		Therefore, all such coordinates are given in terms of a date epoch.
	www.pietro.org /Astro_Util_StaticDemo/CommonAstronomyTerms.htm (769 words)

	Solar Longitude to Date
		Calculate the Julian day from solar longitude referred to equinox J2000.0
		The algorithm is stable between 1900 and 2100 and its accuracy is better than 0.02 days.
	wise-obs.tau.ac.il /~eran/Wise/Util/SolLon.html (27 words)

	BSC5P - Bright Star Catalog
		The annual Declination proper motion in seconds of arc for the equinox J2000.0 in the FK5 system.
		The annual Right Ascension proper motion in seconds of arc for the equinox J2000.0 in the FK5 system.
		See the 'Par_Code' field to determine whether the parallax is dynamical or trignometric.
	heasarc.gsfc.nasa.gov /W3Browse/all/bsc5p.html (763 words)

	R. Hering, H. G. Walter: Updating of B1950 radio star positions
		By rotating the difference vector to the frame J2000.0 and adding to the vector of the calibrator, the updated radio star coordinates are obtained.
		The transformation method discussed here goes back to the difference between the position vectors of the calibrator and radio star at the observation epoch of the latter, since that of the calibrator is normally not documented.
		Comparisons with results based on one of the standard transformation methods show offsets at the level of 5-10 milliarcseconds, which is a non-negligible quantity in modern astrometry.
	www.astro.uni-bonn.de /~pbrosche/aa/acta/vol03/acta03_198.html (261 words)

	EARTH ORIENTATION IN THE INTERNATIONAL REFERENCE SYSTEMS
		As explained in Chapter 1, the mean pole at J2000.0 is slightly offset from the ICRS pole.
		An estimation of the location of the mean pole at J2000.0 is presented p.
		This means that, after calculating the total displacement of the celestial pole using the corrected precession rate and the improved nutation model, a bias in both longitude and obliquity must be added in order to refer to the ICRS pole.
	hpiers.obspm.fr /eop-pc/analysis/consistency.html (1251 words)

	XTE J0929-314: Radio Observations
		M. Rupen, V. Dhawan, and A. Mioduszewski, National Radio Astronomy Observatory, report the detection of a radio counterpart to the x-ray transient XTE J0929-314 (IAUC 7888).
		The source is visible in sky maps computed from 6-day intervals of ASM data.
		R. Remillard, Massachusetts Institute of Technology (MIT), for the RXTE ASM Team at MIT and Goddard Space Flight Center, reports the discovery of a faint x-ray transient at R.A. = 9h29m22s, Decl.
	www.aoc.nrao.edu /~mrupen/XRT/X0929-314/x0929-314.shtml (1000 words)

	b50j20.f
		Ch 3.5 Transformation to the FK5 System and Epoch J2000.0 c This program is based on a PL1 program written by Dr. C.
		I. The Transformation of Astrometric Catalog c Systems of the Equinox of J2000.0" Astron.
	ad.usno.navy.mil /soft/b50j20.f (268 words)

	koko.f
		Use the * routine sla_EQGAL if conversion from J2000.0 coordinates * is required.
		Use the * routine sla_GALEQ if conversion to J2000.0 coordinates * is required.
		"Transformation of mean star places * from FK4 B1950.0 to FK5 J2000.0 using matrices in 6-space".
	www.naic.edu /~pulsar/software/koko.f (866 words)

	PLANET X Moons
		node = longitude of ascending node wrt J2000.0 ecliptic approx.
		i = orbital inclination wrt J2000.0 ecliptic = approx.
		argperi = argument of perihelion wrt J2000.0 ecliptic = approx.
	www.cyberspaceorbit.com /pxmoons.htm (704 words)

	Introduction
		Les dernières intégrations numériques du JPL sont rapportées à un équateur moyen J2000.0 et à une origine des ascensions droites qui dépendent de la construction de chaque intégration numérique et sont différents d’une intégration à l’autre.
		L’origine des longitudes dans ce plan est l'équinoxe moyen inertiel J2000.0, c’est-à-dire le nœud ascendant de l’écliptique moyen inertiel J2000.0 sur l’équateur moyen de la même époque.
		Les théories modernes sont repérées à l’écliptique moyen inertiel J2000.0.
	lareg.ensg.ign.fr /AGRET/chapront.html (725 words)

	ipedia.com: Besselian epoch Article
		The standard epoch that was in use before the current standard epoch (J2000.0) was B1950.0, a Besselian epoch.
		The current standard epoch is J2000.0, which is a Julian epoch.
		Since 1984, Besselian epochs have been superseded by Julian epochs.
	www.ipedia.com /besselian_epoch.html (150 words)

	(meteorobs) algorithm for Solar Coordinates (including sun's true longit
		Then the time T, measured in Julian Centuries of 36525 ephemeris days from the epoch J2000.0 (2000 January 1.5 TD), which is given by: T = (JD - 2451545.0) / 36525 This quantity should be calculated with a sufficient number of decimals.
		= sin E sin S in which E is the obliquity of the ecliptic, which has the value of 23°26'21".448 = 23°.4392911 for the epoch of J2000.0 and 23°.4457889 for B1950.0.
		The method is based on a purely elliptical motion of the Earth around the Sun.
	www.meteorobs.org /maillist/msg09197.html (353 words)

	AIPS HELP file (version 31DEC06) for STARS
		For example, the equatorial coordinate system loosely described as "J2000.0" usually means "the position at epoch J2000.0 on the mean equator and equinox of J2000.0 in the IAU1976 system of coordinates".
		However, the J prefix only indicates the new convention for computing epochs, there is no formal reason to disassociate it from the old Bessel- Newcomb system.
		These are defined by the mean equator (or ecliptic) and equinox specified by the Bessel-Newcomb precession formulae for Besselian epochs, or the IAU1976 system for Julian epochs.
	www.aoc.nrao.edu /cgi-bin/aips/AIPSHELP?STARS (968 words)

	MMTO Observing Catalogs
		The epoch is typically given as B1950.0 or J2000.0
		FK5-0010 0:20:04.251 -64:52:29.25 +26.778 +116.39 4.23 F8 J2000.0
		FK5-0004 0:10:19.257 +46:04:20.21 +00.074 +000.03 5.03 F0 J2000.0
	www.mmto.org /obscats (804 words)

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