That the 8 July Major Occultation in 937AD (Arabic: ٱلْغَيْبَة ٱلْكُبْرَىٰ, al-Ghaybah al-Kubrā) was of the star Hujjat-Allah al-Mahdi, the second occultation after the Minor Occultation.
One way to know for sure is to join us for the RASC Ottawa Centre Zoom-inar Friday 8 July 7:30 PM Eastern Time (US and Canada). I keep offering free beer at the end of these things but no-one has taken me up on it yet.
Anyone looking to look out from this Earth is welcome.
TBC - Allan Jones on Astronomy and the establishing the Canadian border; if you're unlucky it'll be Mick Wilson rabbiting on about some southern hemisphere thing.