Zodiacal constellation boundaries

The heliocentric ecliptic coordinate system of the Human Orrery provides an introduction to astronomical frames of reference. When we designed the exhibit, we wanted the zodiacal constellations to be indicated. However, whereas the Orrery is laid out in the ecliptic plane, constellations are defined in B1875 equatorial coordinates. Therefore for each adjacent pair of zodiacal constellations, we calculated the point at which the J2000 ecliptic intersects the boundary between the two constellations. This point is given in the table, in both B1875 equatorial and J2000 ecliptic coordinates (ecliptic longitude only, since the latitude is zero). All values are in decimal degrees. We see that the largest (in this sense) zodiacal constellation is Virgo, at 44 degrees (its boundary with Leo being at 173.851 and with Libra at 217.810).
Calculations by David Asher with a program that made use of SLALIB subroutine libraries.

B1875		J2000
RA	dec	Longitude
Pisces			numbers	plot	image
25.0	10.381	28.687
Aries			numbers	plot	image
49.25	18.181	53.417
Taurus			numbers	plot	image
88.25	23.430	90.140
Gemini			numbers	plot	image
118.25	20.903	117.988
Cancer			numbers	plot	image
138.75	15.955	138.038
Leo			numbers	plot	image
172.75	3.134	173.851
Virgo			numbers	plot	image
213.75	-13.541	217.810
Libra			numbers	plot	image
237.092	-20.0	241.047
Scorpius			numbers	plot	image
244.0	-21.289	247.638
Ophiuchus			numbers	plot	image
264.0	-23.324	266.238
Sagittarius			numbers	plot	image
300.0	-20.580	299.656
Capricornus			numbers	plot	image
328.0	-12.941	327.488
Aquarius			numbers	plot	image
350.723	-4.0	351.650
Pisces			numbers	plot	image

Strasbourg: constellation boundaries
Jim Kaler: constellations

Last Revised: 2015 February 27th