Here is the story of one of the most famous occultations in history, that of the quasar called 3C 273 , in 1962.
At the time, the objects we now call Quasars were thought by many to be a sort of radio-emitting star with a very peculiar spectrum observed in the optical observations.
Astronomers had already shown that a subset of the powerful radio sources in the 3C catalog corresponded to these stellar-like objects seen in optical observations. However, at the time, the spectra of these objects - as observed in the optical domain - did not seem to make any sense at all!
Using the Parkes radio telescope, Cyril Hazard and his coworkers timed when the powerful 'stellar-like' radio source 3C 273 disappeared behind the moon, and again as it reappeared.
(they actually observed several occultations of 3C 273 in 1962)
They used these timings to obtain an accurate position for 3C 273 that could then be used by optical astronomers so that they could point their optical telescopes at it and thereby figure out "what the object is".
Using the occultation technique, Hazard & Mackey & Shimmins obtained a positional accuracy of better than 0.1 arcsecond for the radio source 3C 273, which at the time was the most accurate positional determination ever made for a celestial object.
With this position in hand, Maarten Schmidt, the other hero of this story, obtained an optical spectrum of 3C 273 with the 200 inch telescope at Mt Palomar.
To his eternal credit, Schmidt realized that the spectrum of 3C 273 was not some weird and inexplicable thing; he came to understand that it was a spectrum that was simply shifted towards the red a long way, indicating that 3C 273 was not just some bizarre star in our own galaxy.....
his interpretation that its high redshift implies that 3C 273 is billions of light years away, has held up to this day.
Here is the full story of this remarkable piece of detective work:
http://www.parkes.atnf.csiro.au/people/sar049/3C273