thank you @Xeerox (i'm having problems with notification srry)
+1 i dont know why people keep unliking save like that...
I didn't get it right, but thanks for responding.
simplified : red shift=wave on phot is turned for the red,ctype is ignored / blue shift=wave on phot is turned for the blue,ctype is ignored / variable red shift=wave on phot is turned for the red,ctype isn't ignored / variable blue shift=wave on phot is turned for the blue,ctype isn't ignored
blue shift = make the spectra blue red shift = make the spectra red __________________ variable blue shift = make the dark blue till blue clear or indigo and violet variable red shift = make the dark red,orange,yellow.
can you explain how variable red/blue shift works? I can't find it anywhere