#21 V_LG

[Dmitry Makarov]

We have to migrate to another apex when calculating correction for centroid of Local Group. We use old correction from Yahil et al. (1977). NED uses apex derived by Karachentsev&Makarov AJ 111, 794, 1996. So, it is a little bit strange that they use my apex but we not :-)

The apex from Heliocentric to Local Group are L_apex=93 deg, B_apex=-4 deg, V_apex=316 km/sec.
The formula is
Vcorrected = V_heliocentric + V_apex * ( sin(B)*sin(B_apex) + cos(B)*cos(B_apex)*cos(L-L_apex) )
where L,B, L_apex,B_apex are in Galactic coordinates

also see
http://nedwww.ipac.caltech.edu/help/velc_help.html