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Topic: Besselian epoch

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Julian epoch

Year

Julian date

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	Glossary of astronomical terms
		Either of the two points (vernal, autumnal) on the celestial sphere where the ecliptic (which is the apparent path of the sun on the sky) intersects the celestial equator.
		See separate definitions for Besselian year and Julian year.) The differences in an object's position when given in equinoxes 1950.0 and 2000.0 amounts to several arc minutes.
		The diminishing of light from astronomical objects due to the earth's atmosphere, in which molecules (air, dust, etc.) of the atmosphere absorb, reflect, and refract light before it reaches the ground.
	cfa-www.harvard.edu /icq/ICQGlossary.html (3582 words)

	[No title]
		Epoch is a Besselian epoch, a Julian epoch, or a Julian
		equinox is a Julian or Besselian epoch e.g.
		Epoch is a Besselian epoch, a Julian epoch, or a
	obswww.unige.ch /~segransa/optique_adaptative/aobprocs/ccmap.html (4656 words)

	ccsetwcs
		Julian equinoxes are prefixed by a J or j, Besselian equinoxes by a B or b.
		Epoch is the epoch of the observation and may be a Julian epoch, a Besselian epoch, or a Julian date.
		Julian epochs are prefixed by a J or j, Besselian epochs by a B or b.
	stsdas.stsci.edu /cgi-bin/gethelp.cgi?ccsetwcs (2744 words)

	Epoch (astronomy) (Site not responding. Last check: )
		The prefix "J" indicates that it is a Julian epoch.
		The previous standard epoch was B1950.0, with the prefix "B" indicating it was a Besselian epoch.
		Besselian epochs were used before 1984, however Julian epochs are now used.
	www.abacci.com /wikipedia/topic.aspx?cur_title=Epoch_(astronomy) (208 words)

	Reference.com/Encyclopedia/Epoch (astronomy)
		The prefix "J" indicates that it is a Julian epoch.
		The previous standard epoch was B1950.0, with the prefix "B" indicating it was a Besselian epoch.
		The "B" in the prefix indicates that it is a Besselian epoch, as opposed to a Julian epoch.
	www.reference.com /browse/wiki/Epoch_(astronomy) (887 words)

	Besselian epoch (Site not responding. Last check: )
		A Besselian epoch, named after the German mathematician and astronomer Friedrich Bessel (1784 - 1846), is an epoch that is based on a Besselian year, which is a tropical year measured at the point where the Sun's longitude is exactly 280°.
		The current standard epoch is J2000.0, which is a Julian epoch.
		Besselian epochs are calculated according to: :B = 1900.0 + (Julian date − 2415020.31352) / 365.242198781 The standard epoch that was in use before the current standard epoch (J2000.0) was B1950.0, a Besselian epoch.
	besselian-epoch.borgfind.com (115 words)

	News \| Gainesville.com \| The Gainesville Sun \| Gainesville, Fla. (Site not responding. Last check: )
		A Besselian epoch, named after the German mathematician and astronomer Friedrich Bessel (1784 – 1846), is an epoch that is based on a Besselian year of 365.242198781 days, which is a tropical year measured at the point where the Sun's longitude is exactly 280°.
		Since 1984, Julian epochs are used in preference to the earlier Besselian epochs.
		The "J" in the prefix indicates that it is a Julian epoch rather than a Besselian epoch.
	www.gainesville.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Besselian_epoch (843 words)

	Epoch Phage (Site not responding. Last check: )
		Besselian epoch - A Besselian epoch, named after the German mathematician and astronomer Friedrich Bessel (1784 - 1846), is an epoch that is based on a Besselian year, which is a tropical year measured at the point where the Sun's longitude is exactly 280Â°.
		Epoch (Chrono Trigger) - Epoch (Silvard in Japan) is the name of the flying time machine the characters of Chrono Trigger use at some point into the game to cross time and space, making their travels easier.
		Epoch is for Chrono Trigger what the airship is for the Final Fantasy game series: a fast and efficient method of transport introduced late into the game to make the few remaining quests easier.
	vi86.maptohealthandwealth.com /epochphage.html (800 words)

	COORDINATES IN THE ASTROPHYSICS DATA SYSTEM
		We don't get into trouble until we insist on referencing time to a year or "epoch" since a year is not an integral number of days (or seconds come to that).
		Thus the Besselian epoch is always somewhat out of sync with the wall calendar (B1950.0 occured at 1950 Jan 0.923).
		Either epoch measure is only a convenient approximation to our civil calendar and the Julian epoch corresponds as accurately to the wall calendar as the Besselian for the first hundred years or so ("standard epochs" are typically updated every 50 years).
	www.ida.liu.se /~TDDB28/mtrl/lab/astro_coord.html (1705 words)

	Julian epoch
		It is often convenient to used the standard epoch, J2000.0, for example, in star catalogs.
		The prefix "J" is added to distinguish this epoch from the more complicated Besselian epoch (see Besselian year) used before 1984.
		The standard epoch is defined as J2000.0 = 2000 January 1.5 = 2000 January 1 12h TDB.
	www.daviddarling.info /encyclopedia/J/Julian_epoch.html (168 words)

	Besselian year concept from the Astronomy knowledge base (Site not responding. Last check: )
		The beginning of a Besselian year, traditionally used as as standard epoch, is denoted by the suffix ".0".
		Since 1984 standard epochs have been defined by the Julian year rather that the Besselian year.
		For distinction, the beginning of the Besselian year is now identified by the prefix B (e.g., B1950.0).
	www.site.uottawa.ca:4321 /astronomy/Besselianyear.html (103 words)

	Besselian epoch Encyclopedia (Site not responding. Last check: )
		position of both receivers at each epoch can be recovered with an accuracy...
		This is done for every epoch until a new GPS satellite is observed...
		DD observation model for a certain epoch (expressed in cycles and containing...
	www.hallencyclopedia.com /topic/Besselian_epoch.html (63 words)

	Year
		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).
		The Besselian year is a tropical year that starts when the mean Sun reaches the ecliptic longitude of 280°.
		An approximate formula to compute the current time in Besselian years from the Julian day is:
	www.starrepublic.org /encyclopedia/wikipedia/y/ye/year.html (969 words)

	[No title] (Site not responding. Last check: )
		Epoch is the epoch of the observation (FK4 system only) and may be a Julian epoch, a Besselian epoch, or a Julian date.
		Users are strongly urged to use the EQUINOX keyword in preference to the EPOCH keyword is they must enter their own values of the the equinox into the image header.
		The Besselian epoch of the observation is 1987.25.
	www-cr.scphys.kyoto-u.ac.jp /member/sakano/manual/man/skyctran (2446 words)

	[No title]
		The epoch is a date needed because RA and declination are measured relative to the Earth's pole and orbit, both of which shift with time.
		The "J" indicates a Julian epoch, as distinguished from the older "B" or Besselian epoch.
		Julian epochs measure the year as 365.25 days exactly, the length of a year in the old Julian calendar; Besselian epochs have 365.2421988 days, matching a "real" (tropical) year.
	www.projectpluto.com /gloss/help_11.htm (0 words)

	imcat: wcscon.c Source File (Site not responding. Last check: )
		Conversions involving 00125 other epochs will require use of the appropriate precession, 00126 proper motion, and e-terms routines before and/or after 00127 fk524 is called.
		at epoch 2000, 00143 and measuring on the sky rather than in terms of dra, the 00144 errors resulting from this simplification are less than 00145 1 milliarcsecond in position and 1 milliarcsecond per 00146 century in proper motion.
		At epoch 2000, 00396 and measuring on the sky rather than in terms of dra, the 00397 errors resulting from this simplification are less than 00398 1 milliarcsecond in position and 1 milliarcsecond per 00399 century in proper motion.
	pan-starrs.ifa.hawaii.edu /project/people/kaiser/imcat_doxygen/wcscon_8c-source.html (761 words)

	Specifying a Co-ordinate Frame
		The epoch may be preceded by a single character, B or J, indicating if the epoch is a Besselian epoch (B) or a Julian epoch (J).
		If a Julian epoch is used to specify the reference equinox for an equatorial co-ordinate system, then the equatorial co-ordinates are assumed to be in the IAU 1976, FK5, Fricke system.
		This epoch is required because some celestial co-ordinate systems are non-inertial and rotate slowly with respect to other celestial co-ordinate systems, introducing fictitious proper motions.
	www.strw.leidenuniv.nl /docs/starlink/sun95.htx/node120.html (603 words)

	Year - TvWiki, 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.
		The Besselian year is a tropical year that starts when the fictitious mean Sun reaches an ecliptic longitude of 280°.
	www.tvwiki.tv /wiki/Year (1674 words)

	slalink.4
		The epoch BEPOCH is strictly speaking Besselian, but if a Julian epoch is supplied the result will be affected only to a negligible extent.
		At epoch 2000, and measuring on the sky rather than in terms of dRA, the errors resulting from this simplification are less than 1 milliarcsecond in position and 1 milliarcsecond per century in proper motion.
		Conversions involving other epochs will require use of the appropriate precession routines before and after this routine is called.
	www.astro.uni-bonn.de /~webstw/cm/lfa_html/starbase/slalink.4.html (0 words)

	AIPS HELP file (version 31DEC07) for REGRD
		Specifying a Besselian epoch to REGRD implies that the coordinates are referenced to the old Bessel-Newcomb/FK4 system.
		An epoch prefix of 'B' indicates the convention that the coordinates include the effect of the E-terms, whereas 'b' indicates that they have already been removed.
		The prefix defaults to B if the epoch is 1950.0, otherwise to J, BPARM.......Coordinate frame and geometry of the output map 1) coordinate frame 1: equatorial (mean of epoch) 2: galactic 3: ecliptic (mean of epoch) anything else defaults to the input map value.
	www.aoc.nrao.edu /cgi-bin/aips/ZXHLP2.PL?REGRD (687 words)

	PICTRANS - Transform a graphics position from one picture co-ordinate Frame to another
		This is the epoch at which the supplied sky position was determined.
		Such values are interpreted as a Besselian epoch if less than 1984.0 and as a Julian epoch otherwise.
		This is the epoch at which the transformed sky position is required.
	www.strw.leidenuniv.nl /docs/starlink/sun95.htx/node352.html (755 words)

	ccfind
		The Internaltion Celestial Refernce System (ICRS) where equinox is a Julian or Besselian epoch e.g.
		The epoch field for the icrs, fk5, galactic, and supergalactic coordinate systems is only used if the input coordinates are in the equatorial fk4, noefk4, fk5, or icrs systems and proper motions are supplied.
		Use ccfind to predict the pixel coordinate in the last example by turning off the object centering, and mark the predicted coordinates on the image display with red dots.
	stsdas.stsci.edu /cgi-bin/gethelp.cgi?ccfind (2531 words)

	Appendix A The Input File
		A Besselian epoch implies the pre IAU 1976 system (as used in the FK4 catalog) and a Julian epoch implies the post IAU 1976 system (as used in the FK5 catalog).
		A Besselian or Julian epoch: a single number resembling years AD, optionally preceded by ‘B’ (for Besselian) or ‘J’(for Julian).
		In the absence of a prefix, epochs before 1984.0 are assumed to be in the Besselian timescale, and epochs from 1984.0 onwards are assumed to be in the Julian timescale.
	www.bisque.com /help/CCDSoft/AfxCore/Appendix_A_The_Input_File.htm (976 words)

	Times
		For approximate purposes, the result of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.
		For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.
		For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 1950.5 is approximately 1 July 1950.
	www.star.bristol.ac.uk /~mbt/topcat/sun253/Times.html (559 words)

	Besselian Epoch to Julian Epoch :: Blocks (Aerospace Blockset)
		The first input is a 3-by-1 vector containing the position in Standard Besselian Epoch (B1950).
		The second input is a 3-by-1 vector containing the velocity in Standard Besselian Epoch (B1950).
		The second output is a 3-by-1 vector containing the velocity in Standard Julian Epoch (J2000).
	www.mathworks.com /access/helpdesk/help/toolbox/aeroblks/besselianepochtojulianepoch.html (0 words)

	Besselian epoch - Definition, explanation
		A Besselian epoch, named after the German mathematician and astronomer Friedrich Bessel (1784 - 1846), is an epoch that is based on a Besselian year, which is a tropical year measured at the point where the Sun's longitude is exactly 280°.
		The current standard epoch is J2000.0, which is a Julian epoch.
		The standard epoch that was in use before the current standard epoch (J2000.0) was B1950.0, a Besselian epoch.
	www.calsky.com /lexikon/en/txt/b/be/besselian_epoch.php (0 words)

	IRAF Help page for "skyctran" (V2.10.4p2)
		EQUINOX or EPOCH contain the epoch of the mean place and equinox for the FK4, FK4-NO-E, FK5, and ICRS systems, e.g 1950.0 or 2000.0.
		The equinox value is interpreted as a Besselian epoch for the FK4 and FK4-NO-E systems and as a Julian epoch for the FK5 and ICRS systems.
		Users are strongly urged to use the EQUINOX keyword in preference to the EPOCH keyword if they must enter their own values of the the equinox into the image header.
	ecf.hq.eso.org /scripts/irafhelp?skyctran (2779 words)

	SLA_PREBN - Precession Matrix (FK4) (Site not responding. Last check: )
		Generate the matrix of precession between two epochs, using the old, pre IAU 1976, Bessel-Newcomb model, in Andoyer's formulation.
		is the star vector relative to the mean equator and equinox of epoch BEP1, M is the
		is the star vector relative to the mean equator and equinox of epoch BEP0.
	www.ing.iac.es:8080 /~docs/external/starlink/sun67/node149.html (50 words)

	Julian Epoch to Besselian Epoch :: Blocks (Aerospace Blockset)
		The second input is a 3-by-1 vector containing the velocity in Standard Julian Epoch (J2000).
		The first output is a 3-by-1 vector containing the position in Standard Besselian Epoch (B1950).
		The second output is a 3-by-1 vector containing the velocity in Standard Besselian Epoch (B1950).
	www.mathworks.com /access/helpdesk/help/toolbox/aeroblks/julianepochtobesselianepoch.html (0 words)

	Times
		For approximate purposes, the result of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.
		For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.
		For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 1950.5 is approximately 1 July 1950.
	www.star.bris.ac.uk /~mbt/stilts/sun256/uk.ac.starlink.ttools.func.Times.html (676 words)

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