Not sure Robin. Molecular absorption will be in the IR 2-20 u looking at my university notes. Interesting thought though.
Images of the target star taken last night (May 01/2), have been added to the page. http://www.stargazer.me.uk/call4obs/29PUK20230507.htm
They indicates an aperture from 8 to 10″ could image the star with exposure 100 to 200ms, even in poor transparency.
I hope some observations will be possible and we get some chords. This will be my last update to the page prior to the event.
To be clear, a “chord” across an asteroid profile is two time points: Disappearance and Reappearance of the star, as seen by the unique position of an observer.
Good luck and clear Skies !