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Old 15-12-2023, 03:28 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 1 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 01:22 PM. Reason: addition
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  #2  
Old 24-01-2024, 10:48 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, 05:41 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 03:10 PM. Reason: new pictures
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Old 29-01-2024, 05:35 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, 11:26 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 01:10 PM.
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Old 08-02-2024, 04:45 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 07:40 AM.
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Old 21-05-2024, 05:30 PM
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Printing mechanicals.. Bracket for motor (with gearbox), mask hinge will be on the shaft 2 mm, also visible on image.

I am still not entirely sure what the electricals will be like, motor needs only 1~1.2 V to rotate with acceptable speed, so there will be a need to regulate Supply voltage to that value.

Also, because of gearbox, the moment is pretty high, and I definitely don't want to crash the mask into C11 corrector plate.
So the limit switches will have to be very reliable and precisely adjusted.
I will do it with camshaft and 1.5 mm pin, which will operate limit switches (hopefully realiably).
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  #8  
Old 21-05-2024, 06:04 PM
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That new design is looking really good mate. I love it...

I'm looking at 3d printers to start tackling some small projects I have planned.. similar sort of things to this, and brackets to hold equipment to my scope/mount.

Any recommendations on a decent starter/intermediate 3d printer?
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Old 21-05-2024, 06:47 PM
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Quote:
Originally Posted by AlexN View Post
...Any recommendations on a decent starter/intermediate 3d printer?
Alex,

I don't know.. I built my own, more that 10 ago, and I still use it.
Have a look at ebay... Jaycar had a good one couple of years ago.
I think any will do, provided it has heated plate and filament motor next to printing head.. they are going for 400~500 AUD
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Old 22-05-2024, 09:11 AM
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This is what the assembly may look like after I print the flaps..
Also it may turn out a single motor will suffice..
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Last edited by bojan; 22-05-2024 at 09:59 AM.
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  #11  
Old 04-06-2024, 11:12 AM
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Testing how critical parts fit into assembly...
So far so good.
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Old 17-06-2024, 01:45 PM
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While waiting for some parts to repair 3D printer, I tried to use test printouts done when it was working OK. I assembled them by gluing them together with acetone..
On the image, limit microswitches are visible. Diodes are below switches, inside the bracket cavity.
If that proves to be functionally OK, I may even decide to keep them as finished product :-)
However, I still need to print the BM flaps.. this has to wait for printer to work OK, hopefully soon (next week).
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Old 21-06-2024, 12:36 PM
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3D printed behaves again.

Test with partially printed flaps, to see how everything fits together (the white collar is only here so hinges are oriented properly and at right distance, it will not be mounted on C11.. (maybe it will))
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Old 23-06-2024, 01:12 PM
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How to prevent the mask falling on the corrector plate, and to force it to fold at the appropriate angle into bracket.
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Last edited by bojan; 23-06-2024 at 02:55 PM.
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Old 25-06-2024, 11:39 AM
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After wiring and a bit of adjustment of limit switches height, it works OK.
It takes ~2 sec to open/close the mask.
Power adapter is 3.3V.
At the moment. I am using 2x3 toggle switch to activate the mask (it provides alternate voltage polarity). Later, it will be done via USB relay board, from desktop computer (already used to control the mount)

Now I need to print the mask segments.
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Last edited by bojan; 25-06-2024 at 03:01 PM.
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Old 25-06-2024, 07:57 PM
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This is coming along really well, Bojan.
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  #17  
Old 26-06-2024, 03:44 PM
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Yes.. slowly.. But surely :-)
The mask (as it is now) is ready for test on telescope (probably next weekend, if weather permits).
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Old 28-06-2024, 04:20 PM
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Test.. Video (zipped webm file) is attached.
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Last edited by bojan; 28-06-2024 at 07:39 PM.
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