J2000 to B1950 coordinate converstion

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Description

Precession from J1950 to B2000

Usage

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j2b(ra = "17:30:30", dec = "-28:47")

Arguments

ra

J2000 Right ascention (string)

dec

J2000 Declination (string)

Details

Enter positions as text strings with fields separated by characters d, h, m, s, a colon, or a comma, e.g. '17, 42, 28', '-28h43m03s', or '- 28 :43 : 3'. Spaces are removed in input conversion. Trailing missing values are taken as zero. The code uses an approximate formula for precession; spot checks give results accurate within a few tenths of an arcsecond.

Value

List with strings in:

ra1950

B1950 Right ascension

dec1950

B1950 Declination

Note

Values based on power-law expansion of more exact calculation.

Author(s)

Andrew Harris

References

Explanatory supplement to the Astronomical Almanac, Seidelmann (ed.), c.~1992, chapter 3.213

See Also

b2j. See dms2rad, hms2rad for input conversions.

Examples

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j2b()
j2b(ra='17h43m', dec='-28d47m30s')
tmp <- j2b(ra='17, 43', dec=' -  28,  47, 30')
str(tmp)
tmp