"O",
The information Dennis has provided above is spot on and spells out the reasons you're better off with a good porro prism binocular in this case, as I indicated in my previous post.
Without going to the extremes of spending $2,000 to $3,000 on a pair of top quality roof prism binoculars, there are several outstanding porro prism binoculars which can be purchased for well under $A1,500 locally, or a lot less if you want to import them from the USA. These will at least equal if not outperform the top roof prism binoculars optically for astronomical and daytime observations. The downside is that ergonomically they are not quite as nice as the roof's, although still very good.
If you can afford a good quality pair of binoculars you should buy them IMO, as I said previously you get what you pay for. Unfortunately the cost increases logarithmically in terms of performance gains.
Some binoculars to consider are:-
Nikon 10x42 SE
http://www.buytelescopes.com/product...88&pid=1890&m=
Nikon 12x50 SE
http://www.buytelescopes.com/product...88&pid=1891&m=
Fujinon Polaris 10x50 FMT-SX
http://www.buytelescopes.com/product...88&pid=9738&m=
You will notice I have linked these to US websites but they are available in Australia.
All 3 of these binoculars would last you a lifetime and are superb optically and mechanically.
Dennis,
In your post you mention that porro prism binoculars have "external" focusing mechanisms making them slightly harder to waterproof and shockproof. Well that used to be true
I have just ordered the 1st "internally" focusing porro prism binocular on the market
Leupold Cascade 10x42 internal focus porros
http://leupold-sports-optics.binocul...ism-44422.html
They should arrive in the next few days
CS-John B