Does anyone know where I can purchase an adapter allow dv recording from a standard telescope mount. Such as an adapter from XL1S to telescope?

It may cost you some bucks, but the better telescopes have available a mount to various brands of SLR's. Many times this is two pieces you need to buy from the scope manufacture, a scope to T-Mount and then a Canon EOS EF T-Mount adapter. Those two adapters will allow any Canon EOS 35mm camera to fit on the scope. Then buy the Canon XL EF adapter and you can attach your video camera to the scope.