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Old 15-12-2023, 02:28 PM
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Idea for 3D printed motorized Bahtinov flip mask

I think I will try to print this for my C11 on first occasion..

The original idea was to print 4 segments, but then I realized 3 or even only 2 will be enough to produce usable diffraction pattern.
The flip segments will be fixed on the steel rope ø1 mm (purple), which will act as a flexible shaft, moved by DC motor.
It is a pity MyFocuserPro currently does not support mask.. Maybe one day it will :-)

EDIT:
It just occurred to me the steel rope could be used as a heater..
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Last edited by bojan; 20-12-2023 at 12:22 PM. Reason: addition
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Old 24-01-2024, 09:48 AM
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Thats cool!

Purely aesthetically, I think the 3 segment design is best - im sure optically 2 would do the job just fine!

What would be cool is an integrated bahtinov mask + flat panel + scope cap.

You could make the 3 circles of the bahtinov mask slightly smaller, and integrate them into one ring, and have the front cap with 3 sub-apertures in it... Rotate the mask rim to the full right limit = sealed cap, rotate to the full left limit = 3 sub-aperture bahtinov mask.

A secondary motor to flip the whole thing out of the way once focus is achieved.

Weight could be a concern, but then on a C11, all your weight is at the rear of the scope anyway, adding a bit to the front wont necessarily hurt...
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Old 24-01-2024, 04:41 PM
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Hi Alex,

Thank you for reminding me of this project, I almost forgot about it

Yours is very interesting idea, I will think about it.. it may be doable to integrate diffraction masks into lid as frame, with motor to flip "mask / no-mask".
As to scope cap, I was thinking about larger one to cover this contraption.. but my 3D printer is a bit small for this (175x175mm), so something big like that must be printed in segments and assembled (glued) later.. and this may compromise the accuracy a bit... probably not enough to preventing it working as lid anyway.

Flats I usually take on the sky before sunset.. so flat panel is lower priority for me at the moment :-)
Anyway.. I started printing it right now.. when finished, and if it fits OK, I will put stl files here.
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Last edited by bojan; 25-01-2024 at 02:10 PM. Reason: new pictures
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Old 29-01-2024, 04:35 PM
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Well, it works OK... especially with brighter stars (I expected that).
Unfortunately, my original measurements were in error, so the ring turned out too small (~6mm..).. so I will have to print the whole thing again.
I also found suitable motors...
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Old 30-01-2024, 10:26 AM
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Control circuit will be simple DPDT relay with additional diodes and limit switches (like on attached schematic), or USB relay board (application works only with 32-bit windows, which is OK with me).
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Last edited by bojan; 31-01-2024 at 12:10 PM.
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Old 08-02-2024, 03:45 PM
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After some more experimenting, I changed the concept somewhat..
This mask has larger area (so diffraction spikes will be more prominent) and when not in use it fits under the original C11 lid.
During exposure, each half of the mask is folded around shaft inside dew cap.
I plan to add the end parts as well, to make the mask completely cover the aperture when used.. but a trouble adding those additional 8 slits and hinges may not be worth really..
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Last edited by bojan; 09-02-2024 at 06:40 AM.
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