RE: Re: [guide-user] Great Red Spot longitude setting

jarisuomela Oct 12 8:52 AM

Hi Bill,

I recall reading that Robert Hooke was the first to spot the Spot in 1664. A quick web search dug up an interesting illustration by a bunch of people in Rome in 1665 . It shows GRS with the shadow of Ganymede. Could that information be used to add one more data point?  The challange would then only be to fill in the missing less than two centuries <G>

The above article also mentions that G. D. Cassini published a table of GRS transits in 1665. If one could get a hand on it...

Kind regards,


---In, <> wrote:

 (I also revised an error I made in the explanation at the end of the file, in which I suggested that perhaps we could find data going back to Galileo. I mis-remembered my history; Cassini probably observed the GRS, but then there's a gap until 1831.So I don't expect us to be able to extend the table before then.)
-- Bill