As Marc discovered, the Original Poster linked to an example photo that was taken with a 28 mm lens. On a Pentax DSLR it would be roughly like a kit lens 18mm.
People have offered several mount suggestions. A Barn Door mount is cheap, especially if you build it. OTOH it is single purpose. It can't do much else but wide angle astrophotos. Next step up is an equatorial camera mount, there are a few on the market. In my opinion they cost more than a small motorized telescope mount. Next step is a motorized, "German Equatorial Mount" for perhaps $150 that could be used for a camera and would also handle a small telescope in the future. Finally, you could buy a modest telescope with motorized mount to which the camera can be used "piggy back" with a lens as well as on the scope for high power. This is the most versatile and you might actually find you enjoy astronomy.
Hint about Equatorial mounts: They must be Polar Aligned. Be sure you get instructions for whatever mount you choose. OTOH the camera need not be precisely aligned to the mount. My camera mount is about 5 degrees off from the axis of the scope and it makes no difference.
Next obstacle is exposure time. Where I live the light pollution limits me to 1-2 minute exposures with my modified K110D. This is way to short to approach the example photo. To get a long total exposure you pretty much have to stack multiple images. Or image from a really dark location on a cool night.
Here is a Milky Way photo taken from my light polluted back yard using a K110D, Vivitar manual 19mm lens, PiggyBacked on an 8 inch Meade SCT. Eighteen exposures of 120 seconds using in camera Noise Reduction. Not nearly as good as the example. I hope to have another chance from a dark site.
http://henriscorner.com/leosfolder/mwupper.jpg
Astrophotography is very dependent on processing. Software designed for astro is preferred since the needs are very different than daylight photography.
BTW: the K20D's not being able to turn off NR is not a show stopper. It doubles how long it takes to get the same total exposure, but it is simpler than working with dark frames. Taking multiple dark frames would be a little better. I tend to use in camera NR for the Pentax vs a few dozen 15 min darks for my SBIG camera.