Yeah nightstalker I know many people could build somethign for themselves, and have done so already, that ended up being way cheaper than this. I have neither the time nor inclination to get into a project that complex because (as I'm pretty sure my grade 10 woodwork teacher would say) "it would be a mess".
I used the 2.5 metre diameter $2k unit delivered as an example, I'd personally be using something smaller myself when the time comes, but I was making a more direct comparison size and price wise to the a 2.3 m Sirius dome, priced at $6k here in oz, making the water tank conversion a MUCH cheaper idea!
During my research a while ago I found the website for this company in the US:
http://www.explora-dome.com - their dome sells for US$650. That's right, basic dome structure with slide open sky hatch for $650. Surely we can come up with something in this, the "Clever Country" that is a bit more realistically priced!
More great images here:
http://www.explora-dome.com/View_Exp...e_Pictures.cfm
As suggested by Miaplacidus I have already considered talking to existing water tank manufacturers re a possible partnership in dome making, but as Paul, Dennis, etc have already pointed out there is gold in water tank manufacture at present.
Interestingly the Exploradome / Polydome people started out as - yes, water tank manufacturers! It all uses the same kind of polyethylene rotomoulding process, and they now have close to
200 different products in their lineup.
Click on this link and scroll about 2/3 of the way down to read how the astro domes began after an amateur astronomer approached them with an idea:
http://www.pappasgrills.com/exploradome.aspx
I still think there's a great opportunity in here somewhere, and I'll continue to follow through on this idea in the future and see what I eventually come up with.