All very valid points, well explained and researched by the looks of things, thanks to all for the comments and the thought....
So after all this, it seems to boil down to.......
"Stupid" Edmund Halley taking a "twinkle" on a canvas some poetic artist licenced to him while he was under the influence of magic mushrooms to treat his astigmatism which made him quite "cross"?
That sound about right? - good, now we can all get some sleep.
Thanks everyone
Cheers
Chris