changed how inital guess is obtained from input wcs
changed how inital guess is obtained from input wcs

dhomeier/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,MSeifert04/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,larrybradley/astropy,astropy/astropy,MSeifert04/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,lpsinger/astropy,astropy/astropy,StuartLittlefair/astropy,stargaser/astropy,saimn/astropy,stargaser/astropy,dhomeier/astropy,astropy/astropy,pllim/astropy,mhvk/astropy,StuartLittlefair/astropy,saimn/astropy,dhomeier/astropy,StuartLittlefair/astropy,mhvk/astropy,mhvk/astropy,larrybradley/astropy,stargaser/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,saimn/astropy,larrybradley/astropy,saimn/astropy,mhvk/astropy,stargaser/astropy,larrybradley/astropy,mhvk/astropy,astropy/astropy,MSeifert04/astropy,pllim/astropy,saimn/astropy,astropy/astropy,pllim/astropy,pllim/astropy,larrybradley/astropy,lpsinger/astropy,pllim/astropy