I have a colourbond clad ROR which has an enclosed half and an open half.
My suggestions:
Keep thermal mass to a minimum so it cools down quick. Let it heat up in the day as long as it cools down at night.
My insulated enclosed half heats up less than the open half (36 degrees vs 42 degrees on a hot day) but as soon as the sun leaves the observatory in the afternoon the un-insulated half immediately (I mean very quick - within 10-20 minutes) drops BELOW the outside temperature as heat is quickly radiated out by the colourbond metal. By the time night comes and I open the roof the telescope is comfortably cooled from the hot day, I feel. The insulated half slows down slowly and never fully cools. I have a reasonable size exhaust fan in the insulated half which has some but minimal effect on speeding up the cool-down time.
Even if your whole ROR rolls off, I think the insulated walls would continue to hold heat through the night, which colourbond on its own doesn't.
Use white. I used "wheat" colour Colourbond (which is a very light colour) and after painting the roof white observed a significant reduction in heat (42 degrees vs 50 something degrees on hot days). I have white shade cloth down the northern wall too now.
I personally don't see the need for the extra layer of wood, I would just go with colourbond, paint it if you like. If you want a nice look to the inside by lining it, I'm not sure what would be best exactly. I used fibro to line the inside half of mine when I insulated it. It is nice having it lined, makes it a cleaner neater environment, but the tradeoff is the slow/absent cool-down. Perhaps if doing it again I'd put the same fibro lining on but not use insulation. In winter the inside half is nice and cosy, the insulation and lining does a great job. Very glad I kept the open half bare Colourbond though.
Have fun and don't be too fussy, I've found it's easy to be too pedantic about technicalities of permanent mountings/observatories, worth sometimes just going with what works for you, ease and cost, and making what you have work.
. I am currently in the planning phase and looking at my options to clad. Currently the plan is to clad it first in ply then screw the colour bond cladding over the ply. Are there any drawbacks to this or any thing else I should be adding between the colourbond / ply or the ply / frame ?
