OPT was able to send me another unit. While the filters did not thread all the way in, unlike the first unit they started easily and threaded at least 50% of the thread length before binding. While this is not ideal, I am satisfied that this 2nd wheel will hold the filters securely and all will work well.
I appreciate Sam's point. Amazingly there does not seem to be one standard and since I had this problem I have learned that this issue does crop up from time to time.
If I might make a suggestion. Apparently if there is a standard it seems to be the imperial measure one -- but I certainly have found no convincing evidence. Let's say for the moment that that is true. Then clearly it does not convert into an exact metric standard (What the hell was the US thinking not converting to metric????). ZWO uses M28.5x0.6. That seems very sensible. Sam said they had problems at ZWO with threads cut too loose. Clearly there is variability in manufacturing because my distributor had two units - one that "worked" and one that did not. Also, from my research a user at Amazon had the same issue and his distributor found that about half of their stock on hand worked and half did not. Perhaps there are multiple taps cutting these wheels and one "works" and one done not. Hopefully ZWO can get to the point where they are turning out identical threads.
My suggestion, for ZWO and anyone trying to mate with this not so standard 1.5" filter thread standard, is err on the loose side when you choose tolerance. We users can all wrap a tiny piece of teflon tape around a male thread and snug it up. Or even put the smallest touch of LocTite Blue on the thread and solve the too loose case in a completely reversible way. What very few of us can do is take the part into our machine shop and mill out a tiny smidge of metal.
So, why not choose the loose side of the tolerance range so the user can "fix" it trivially if need be rather than the tight side that probably less than 1% of the users can fix??
Anyway, I'm all set with my filter wheel. My suggestion just food for thought.
And here is one more thought. The ZWO filter wheel make no attempt to baffle the open part of the wheel where the carrier sticks out for rotation. That leaves a very substantial gap for light from the side to enter. Now, we all image at night so this is probably a non issue. But when I am not around others just running imaging and not visually observing I like to not run my laptop in red mode because I find the normal bright white screen much easier to read. So, I do have some white light bouncing about.
I'll probably do something about that like secure a small length of weather stripping inside the front cover so it blocks much of the gap. ZWO might want to consider adding a baffle to the front cover -- and the body too if they ever redesign this part. They could eliminate almost all of the gap without causing any problem with rotating the wheel.
Thanks for your response Sam. Since I have a wheel that will work now I do not need to have you intercede on my behalf with your distributor.
Richard
