Plenty of GRS early history here...... https://archive.org/...upiter/page/n69
At times it has seemed covered in white cloud, but clearly present, as it’s oval outline or the bay in the SEB(S) was indicating...........see from page 132 of the above-linked Peek’s book.
I tend to go along with a notion of John Rogers (BAA Jupiter) that the Spot is cyclical – or not even the same one as first definitely recorded. He seems to doubt Hooke’s 1664 spot more favouring Cassini’s 1665 one:
“There were no [sightings] of any such feature between 1713 and 1831 – an apparently unbridgeable gap.” (“The Giant Planet Jupiter (Rogers) – page 6).
Rogers also doubts the 1879 recognition as being the old Cassini spot. His book shows early drawings from the mid-1860s-on that show it as a very long ellipse (‘lozenge’) about 1/3rd the length of the visible STrZ. Renditions by such as Antoniadi, Philips et al; some of who likely could have out-sketched me standing on their heads – unlikely to be artistically inaccurate.....!
Such a length against its steady contracting over the decades suggests to me a relatively recent formation/re-formation back then.
I’ve been recording it through many shades (sometimes bi-coloured or shaded-off northwards) of deep orange-red to pale pink to yellow-orange (ochre/tawny even) since the early 1960s and was perhaps nearest to fully deep red in 1964/65 (to me).
Now off out to catch the planet.......no GRS from here tonight..........