# Estimating the tangential and cross component of the galaxy's shear using Gnomonic projection

I would like to know how I can estimate the tangential and cross component of the galaxy's shear using Gnomonic projection of the right ascension and declination the galaxies relate to the center of galaxy cluster and estimate ?

-
Please elaborate what you mean by shear? When I read the title I thought about the shear in the galactic velocity fields and Oort's constants ... –  Walter Sep 5 '14 at 9:59
@Walter shear is the second order moment of galaxy's surface brightness. You can find more exclusive explanation here –  Dalek Sep 5 '14 at 10:26