Canon 40D lens question

[dugnsuz (Doug)]

Hi all,
thinking of buying a Canon 40D camera body.
I have a Sigma K mount lens (Pentax) for daytime use. Is there an adapter I could use to fit this on to the Canon? A google search came up with not much - makes me think it's a no-go!
Please help - do I buy the body or body+lens kit!?
Cheers
Doug

[dugnsuz (Doug)]

PS - the kit lens is a Canon 17-85mm EF IS USM Lens
I reckon this would be fine for daytime stuff, but would it be any good for piggyback photography?
Cheers
Doug

[dugnsuz (Doug)]

PPS - Googled my own question!
Looks like any adapters are just going to give me manual control over lenses. Wife and Kids have grown very used to the automatic nature of the Pentax DSLR, so an automatic lens for daytime stuff is a necessity - kit lens for daytime.
Question still on table is - is the lens any good for Astro work?
Doug

[acropolite (Phil)]

The 17-85 IS, despite it's higher price, isn't all that good a lens. The sigma 17-70 f2.8-4.5 is reported to be as good if not better optically, at under half the price of the 17-85, but doesn't have IS. If IS isn't a consideration you would be better to but the 17-70 and spend the difference on a 50mm f1.8 lens ($100-150 depending on wher you buy), they are a very good lens for the money and on a 2/3 format DSLR they make a nice fast protrait lens as well.