Before the upcoming Pentax DA 560/5.6 comes and if you really need one, here is already an alternative option, i.e., the Samyang/Walimex 650-1300/8-16 telescope:-
http://www.mediaresort.de/shop/en/Lenses/for-Pentax-Samsung/walimex-pro-650-1300-8-16-Tele-for-Pentax-Samsung.html
The "lens" can be mounted onto a K-mount body via an T to K adaptor. It is sold at 299 Euro or a bit more than 300 US$. Here are some reviews of it, don't expect stellar optical performance, though:-
http://dpanswers.com/roztr/lens_show.php?id=368&pid=WA6501300&s=Canon
http://www.amazon.de/dp/B001UAIERU?m=A3JWKAKR8XB7XF&tag=idealocom
And two sample pictures taken with it:-
(at 650mm)
(at 1300mm)
Source: http://item.taobao.com/item.htm?id=1930380686
(The Scene)
So, adapting a telescope to a DSLR/ILDC may or may not be a good idea. That depends on what you want actually. It offers a cheap solution for a very long reach, nevertheless.
Read Also:-
Total Lunar Eclipse (2011-12-10, at Hong Kong)
O-GPS1 Astrotracer Examples