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Old 01-07-2019, 08:48 AM
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DIY turret for C11

More than 35 years ago a friend made this turret for use with MTO 1000A (my design, material was PVC).
Unfortunately, he was not careful enough when machining the holes for eyepiece barrels, so all three are offset by ~3mm. Not a big problem for visual at low power, but because of this turret spend most of its life in the drawer.
I decided to 3D-print the more accurate version (I need to do only the rotating part), and for 4 eyepieces (it will be easier to balnce it properly)
To achieve the smooth rotating, I will finalize the inner surface on lathe.


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  #2  
Old 01-07-2019, 08:50 AM
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You never cease to amaze Bojan. Great idea and an even better save.
Alex
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Old 01-07-2019, 08:39 PM
Wavytone (Nick)
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Hi Bojan, nice idea to print one.

How will the fit onto the C11 ? Screw on ?
Also Id suggest one of the eyepiece barrels be 2 otherwise its going to be a bit limited on the C11. I have a TEC turret which only takes 1.25 and for this reason I only use it on scopes smaller than my MK91 - which has a similar focal length - and I find I really do need one big 2 low power eyepiece at around 90X.
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Old 01-07-2019, 09:51 PM
garymck (Gary)
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https://www.thingiverse.com/thing:1433034

cheers
Gary
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Old 02-07-2019, 07:24 AM
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I am re-using central part of existing, old turret.. it was made to fit MTO adapter (which acepts M42x1 or M39x1 thread barrels), so the hole is a bit larger than 2" thread. I already printed the interface (without thread - it is fixed (but adjustable) onto C11 2" thread by 3 screws for now, in the future I will make proper metal screw adapter).

Fitting 2" eyepiece is another matter - I have only 1.25", and I don't have suitable mirror at hand, and even if I had the larger one, it wouldn't fit inside existing barrel... so I will stick to what I have at the moment.. It is not hard to print another one anyway in the future, it only takes time (this adapter used 6 hours to print @99% fill)

Gary, thank you for the link, I knew about this design (whenever I need something to do by 3D-printing, I always check Thingiverse first - if not for suitable design, then for ideas). I was considering it but..
To fit 6 eyepiece barrels, the hub of this design needs to be quite large (and even larger for 2" eyepieces), so the optical path is significantly longer than optimal backoff for C11.. my design as it is has that distance much closer to recommended value.
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Old 02-07-2019, 03:43 PM
Wavytone (Nick)
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Dont think of 6 - the Unitron Unihex had 6 and it was big and heavy.

I have a TEC turret - 5 x 1.25 with a 2 frontend, and this has some sort of epoxy body to save weight and keep the size down. The eyepiece barrels have to be slim too.

With turrets size and weight are a serious issue - by the time one of these is loaded with a full complement of eyepieces and possibly a camera it could exceed 4 kg and if you rely on a typical crayford it may not hold this load - and worse it may tear the focuser off the scope.
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Old 02-07-2019, 08:49 PM
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No worries Nick, I am not thinking of 6, only 4x1.25".
3x was OK (apart from non-coaxiality issue), so 4x won't be too much worse.
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