[lister6520]

Most lenses focus past infinity. The lens infinity mark is indeed temperature dependent as well. The only way to critical focus a lens at infinity in darkness, particularly at wide apertures, is focus on the sensor itself with magnified live view. Use bright star or any other bright light at infinity to focus on.

I think you have misunderstood the problem being reported by rcolman. The issue here is not how to find the focus but that when fitted on his K1 the lens reaches the end stop, at or beyond the infinity mark even before it has actually reached infinity focus. In other words it is mechanically impossible to focus the lens at infinity no matter how hard you try.
No bright star in live view is going to help with that. It would need something more like a large monkey wrench to grab the focus ring and force it to turn a few degrees further.

[biz-engineer]

why would you produce a camera that could not manual focus properly at infinity,

Why don't you fly to the stars, then it's not as far as infinity. Although, I agree; taking a space shuttle to photograph stars closer is a lot more expansive than fixing a camera and lens :-) Better talk to Ricoh after sale service directly.

[GUB]

4) many other reports of the same problem

Could you give links to these other reports? It may help us see what the problem is here.

[RobA_Oz]

Well, that's that, then. The OP has done what he seemed determined to do from the first post. It's a pity he didn't ask others for help before posting a dramatic exit, and then batting away any suggestions with what effectively amounts to "I know what I've been doing for forty years, and the problem isn't me". Having trawled through this thread and the thread in DPR (what a painful way to follow conversations!) I'm left scratching my head that someone who is a (fellow) mechanical engineer and who was willing to spend a lot of money following a set of specifications on paper didn't research the camera to find the alleged existing and widely-noted problem before doing so, let alone be willing to do some physical measurements to confirm that registration tolerance was the problem.

Who knows? Unless the problem also surfaces with the keen Astro-photographers here, we're not going to find out by pursuing this thread.

By the way, I agree with MightyMike's assertion on DPR that the OP's Sony image posted appears to show star movement. I might add that the K-1 image posted alongside it appears to show coma, so the whole basis for this thread is inconclusive, and we are left to ponder the OP's assertion that he knew what he was doing.

No offence intended. I'm not saying he didn't, just that the case wasn't made convincingly.

[wombat2go]

let alone be willing to do some physical measurements to confirm that registration tolerance was the problem.

I agree. With these short focal terrestrial lenses, half an hour doing daylight tests like I did this morning in post #19 at a few hundred metre and various f/- would probably point to the problem.
" One test is worth a thousand expert opinions" - Von Braun , very applicable to these kind of internet threads.

[Parallax]

I am done, out, thank you very much.