after getting advice, anti-graffiti paint (white) was applied to the horizontal grey poly surface and has lasted 2-3 years.
The internal surface temperature was lowered ok.
Touch up with a spray can (primer/finish external) is now indicated.
This observatory will be soon replaced by a larger roll on/off.
If interested refer:
http://www.iceinspace.com.au/forum/s...d.php?t=153209