What overlay are you using?
Viewing post in Thunderstruck! [Vectrex] comments
It's one of Laurence's UV overlays, albeit not lit with UV. https://www.blacklighter.co.uk/overlays
Hehe, oops! Luckily my friend Jim has just produced some more UV frames - contact him at http://www.clockworkrobot.com/shop/ should you be interested in buying one.