OK, I'll keep and use both these Cheshires (both are called "collimation tools"). I spent a while with them last night and during the day today. I'll use them together with my collimating laser.
In summary, I'll use the Orion primarily for checking secondary mirror position. I'll use my laser collimator as the main tool for secondary and primary mirror tilt, including barlowing it to confirm accurate primary mirror tilt. I'll confirm with either Cheshire tool, but I'll use the "Chinese" Cheshire primarily for checking collimation in the dark.
A couple of comments on the two tools, Orion and "Chinese". The Orion is clearly a better machined product and has the additional length and the crosshairs. The "Chinese" is mostly plastic. It has grooves on its end to which crosshairs could presumably be glued, if one wanted, but given its short length, the accuracy would be questionable, and they are exposed so I suspect they would soon be bent or otherwise damaged.
The Orion is a snug fit in my 2"-->1.25" adapter. The "Chinese" needed two ridges arising from the mould which formed the plastic body scraped off. It was too loose in the adapter, but one layer of contact fixed that.
I now understand my confusion. The second and third attached pictures (apologies - small point and shoot with poor control over focus or exposure) show that the "hole" in the Orion that forms the dark spot in the shiny reflection is considerably larger than that in the "Chinese". The "Chinese" produced a small spot which sits neatly inside the ring centre spot on my 8" and the triangle centre spot on my 12". The dark spot from the Orion overlaps the ring and triangle considerably and makes it more difficult to accurately overlap them - it's probably just me, but the small "Chinese" spot was very easy to align, especially in the dark using a redlight torch for illumination. Additionally, the presence of the crosshairs and their reflection in the view did not assist me in centering the dark spot on the primary mirror centre.
I did lots of experimentation with all three tools - rotating them in the adapter, rotating the adapter in the focusser, racking the focuser in and out. All three show good consistency - not german engineering accuracy, but nothing went dramatically wrong with the reflections or return laser beam when I did all these things. For me, a visual newbie, I reckon that is all I need at present.
Yes, and I checked the laser collimation result with each Cheshire in turn. Again close enough for my purposes. If the Secondary hasn't been knocked out of position (eg rotated on the centre screw while bouncing to darksky site), I trust my laser to give me a good result. I'll check it with either Cheshire and tweak, but the "Chinese" after dark is my preference.
(Yes, and I have a v-block made up on which I check my laser's internal collimation over a distance of several metres every so often - certainly after battery change.)
Any collimation of a newtonian reflector is obviously better than no collimation, and I don't believe one needs to spend too much money or expend too much effort to get a good result for visual astronomy for a relative newbie like me.
My 2 cents worth!
