This plot compares my measurements against the median measurements done by the other users. NOTE: In general, +/-5 degrees scatter is OK. You need to be more careful to increase your accuracy and reduce the scatter. In particular, you need to be more careful when it comes to low inclined (more face-on) galaxies. We know that the uncertainty is larger for more face-on galaxies. In order to decrease the uncertainty, just make a 3-dimensional mental picture of galaxies in your head and try to make sense of their inclinations. Just imagine how you can rotate a round flat disk in space to create the 2D projected image you see.