The J.F.B. Observatory

Filter_wheel

A homemade manual 4 position filter wheel:


I recently made this filter wheel to accomodate my R,G,B filter set for LRGB imaging:

 

It is loosely based on a 3-View picture I had of the ATIk 5 position wheel and

an idea I had in my head about what should go where.

The picture sequence shows how I went about it.

 

 

The ATIK wheel is 19mm tall. I had trouble keeping mine this thin.

Filters only just have clearance from scraping the inside surfaces of the housing.

It ended up being 19mm thick, without the adaptors either end attached.

I had a few options to adapt: I cut a 28.5mm thread both ends.

As one turned out a bit dodgy, I decided to adapt to the 1.25mm nosepiece with

an aluminium flange. This added 3mm in thickness.....19mm became 22mm.

I cut a 42mm T-thread in this flange for the nosepiece.

 

 

Then I added another flange the CCD camera side....again, I could have just

made an adaptor to screw into the 28.5mm filter thread, but decided to save

time and just make a flange....this adds another 3mm...so 25mm in total.

I was going to motorise it with a small DC motor and reduction gearbox that

I had from an old Handicam focus mechanism.

 

However, I just ended up knurling a thumbwheel surface on the platter in the

end. A miniature bearing sits on a spindle turned up from a 5mm set screw.

It revolves a little too freely, so I introduced a bit of friction by laying a kevlar

miniature toothed belt inside out around the circumference of the cylinder

housing.

The knurled platter just rubs against it enough to provide some friction.

 

 

I could modify or add another platter very easily. As a prototype, this one turned out very well.

Again, motorising could be easily added later also.

 

 

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