There was a thread not long ago, started by Joshua Bunn, about proposals for custom adapters, but I can't find it. Peter Ward suggested that an 8 to 12mm nonrotating adjustable spacer would be useful for nailing the optimum spacing between a focal flattener and camera on certain astrographs.
I proposed a design which had some chance of working but looked rather difficult to make.
My problem is that I can't resist a good engineering challenge, so I went ahead and tried to make one.
The result is in the attached images. It works reasonably well, maintaining parallelism within about 25microns over 80mm diameter, but unfortunately it requires the use of a 3mm Allen key for locking. I intended to use an 8mm diameter thumb screw for locking but there is too much play in the threads for that, as the lock relies on radially distorting the red ring.
Bloody hell. That looks incredible. How did you do it??
(As in, what tools did you use - I presume you have milling machines / lathes / thread cutters / etc to work with...)
Cheers,
V
Thanks V,
A lathe, a milling machine and a CNC engraver for milling the lever.
All simple machining operations but a lot of them, requiring many setups.
Amazing skills well done! So…are you taking orders?
Thanks Dave,
Good question.
I don't have any astro gear that uses such crazy treads so I will probably just keep it on the shelf as a conversation piece. And I don't think I will make any more because no one would like the price based on how long it takes to make.
Perhaps I should add it to the products on my website, but not for sale, only to be borrowed by people who have trouble getting the camera spacing right. Once the spacing has been determined, then a much cheaper fixed thickness spacer can take its place. Another idea would be to just sell it on IIS for an arbitrary amount.
There was a thread not long ago, started by Joshua Bunn, about proposals for custom adapters, but I can't find it. Peter Ward suggested that an 8 to 12mm nonrotating adjustable spacer would be useful for nailing the optimum spacing between a focal flattener and camera on certain astrographs.
I proposed a design which had some chance of working but looked rather difficult to make.
My problem is that I can't resist a good engineering challenge, so I went ahead and tried to make one.
The result is in the attached images. It works reasonably well, maintaining parallelism within about 25microns over 80mm diameter, but unfortunately it requires the use of a 3mm Allen key for locking. I intended to use an 8mm diameter thumb screw for locking but there is too much play in the threads for that, as the lock relies on radially distorting the red ring.
OK so is it for sale? Interested in making another one? & how much.... please pm me...I'm obviously interested !
If you need it to determine the optimum spacing on a particular optical train, why don't just borrow it and then have a custom spacer made. A simple spacer can be made to very accurate specs with no wedge error.
If you need it to determine the optimum spacing on a particular optical train, why don't just borrow it and then have a custom spacer made. A simple spacer can be made to very accurate specs with no wedge error.
Ah...if life were so simple. I use multiple OTA's, field correctors, filter wheels and cameras. I can usually get with +/- 3mm using stock parts...and have a custom spacer or two to get within 1mm. A rigid spacer that I can adjust and assess optically would be extremely helpful....
That looks great Stefan, nice colour scheme to I hear you on the multiple setups and the work involved.
Peter, I haven't forgotten, just catching up on other orders. If you would like something similar for this purpose, I would be more than happy to to make you one.
Last edited by Joshua Bunn; 10-08-2022 at 01:27 AM.
Ah...if life were so simple. I use multiple OTA's, field correctors, filter wheels and cameras. I can usually get with +/- 3mm using stock parts...and have a custom spacer or two to get within 1mm. A rigid spacer that I can adjust and assess optically would be extremely helpful....
I see. PM me an address and I'll send it to you for testing. If it does the job, we'll take it from there. I don't want to sell untested prototypes.
The specs of the 2.7" AP thread circulating on the net, apparently disclosed by AP, are very unsatisfactory and would result in very loose fitting threads. I made a bit of a guess regarding those specs and I would appreciate feedback on how well they match original AP gear.
Well, it turns out that this contraption can be used only on astrographs that use a guidescope for guiding. The locking mechanism can't rotate past a typical OAG camera focuser.
Well, it turns out that this contraption can be used only on astrographs that use a guidescope for guiding. The locking mechanism can't rotate past a typical OAG camera focuser.
Stefan kindly gave me that unit to beta test.
Despite the literal OAG snag, the fit and finish is very polished.
He does superb work
How I wish that standard could be universally seen in my "made in China" bits & bobs.
That is a really great piece. 8-12 sounds good. Does weight add any flex (and therefore tilt) to the train? My image train goes as follows
Esprit > Esatto > extension > adapter > flattener > adapter > manual rotator > QHY spacers > filter wheel > camera.
Something like this part would take the place of some of my QHY spacers but not all... I feel that could be too much? unless this will hold the weight of the filter wheel and camera without introducing tilt?
I hear you on the multiple setups and the work involved. 
