Hi Mona,
This joke certainly was worth a smile - and I would say it is based on a true experience had by some poor Astronomy lecturer ... though the message is mixed, and doesn't sound too sensible, there is no reason to suggest that 'onomy and 'ology are still not confused by many.
Of course it could also have been a prank by a serious student who hadn't prepared for his test or it could also have been an attempt to put Astrology 'in it's place.'
It also reminds me of that comment made by Isaac Newton when taken to task about his interest in Astrology. Newton is reputed to have said something like "The difference between us Sir, is that I have studied it and you have not!"
The more we know the less we know or the more we know that we don't know. Time to take a breath. Loved your article, thanks.
Cheers now