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diff --git a/noao/astutil/asttools/astvr.x b/noao/astutil/asttools/astvr.x
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+include	<math.h>
+
+# AST_VR -- Project a velocity vector in radial velocity along line of sight.
+
+procedure ast_vr (ra1, dec1, v1, ra2, dec2, v2) 
+
+double	ra1		# Right ascension of velocity vector (hours)
+double	dec1		# Declination of velocity vector (degrees)
+double	v1		# Magnitude of velocity vector
+double	ra2		# Right ascension of observation (hours)
+double	dec2		# Declination of observation (degrees)
+double	v2		# Radial velocity along direction of observation
+
+double	vx, vy, vz, cc, cs, s
+
+begin
+	# Cartisian velocity components of the velocity vector.
+	vx = v1 * cos (DEGTORAD (15. * ra1)) * cos (DEGTORAD (dec1))
+	vy = v1 * sin (DEGTORAD (15. * ra1)) * cos (DEGTORAD (dec1))
+	vz = v1 * sin (DEGTORAD (dec1))
+
+	# Direction cosines along the direction of observation.
+	cc = cos (DEGTORAD (dec2)) * cos (DEGTORAD (15. * ra2))
+	cs = cos (DEGTORAD (dec2)) * sin (DEGTORAD (15. * ra2))
+	s  = sin (DEGTORAD (dec2))
+
+	# Project velocity vector along the direction of observation.
+	v2 = (vx * cc + vy * cs + vz * s)
+end