Iv'e noticed The Isle of Man from Greycroft stone circle Cumbria and Holyhead mountain Anglesey and rather fancy that it can be seen from everywhere around the irish sea.
If it really does become invisible perhaps it's the inspiration for Atlantis
Once you get a bit of altitude it's visible without light tricks, but from sea leavel it's beyond the horizon. I've often wondered if this is one of the reasons for its mystery....