I have just been reading in the current edition of AS&T that in 1679, the french Astronomer Augustin Royer, formally split Crux from Centaurus. In 1679 ACrux sat at a declination of -61deg. (currently -63deg.) thus the furthest north on Earth, one could see Crux just sitting on the southern horizon would be 29deg. For a french astronomer to see this constellation he/she would have to travel due south until arriving somewhere in the middle of Libya or Algeria, or some other country sitting on this latitude.
Does anyone have any information on how/where Royer got to see Crux, or have I got my calculations wrong?
Robert