Telescope Filter Cap (Parametric)

This is a filter holder/cap for a 5" outside-diameter optical telescope.

My specific use-case is for a solar filter ahead of the total eclipse in April, 2024.
 

The assembly is pretty straight forward.

The Filter is sandwiched between the Inner Ring and the Outer Ring.
Then there are Inside and Outside Covers to protect the Filter in storage or transport.

There are 3x 2mm holes pre-defined in the Outside Cover and the Outer Ring for screws which serve two purposes.

The first is to allow attachment of the Outside Cover to the Outer Ring.

The second is to lock the Inner Ring and the Outer Ring together to prevent the Filter twisting if the two rings were to move against each other.

You only have to tighten the screws enough to stop the movement of the Inner Ring.  Anything more than that and you risk damaging it.

Once everything is put together, it will look something like this:

The big part to remember, is that after cutting your filter, place it silver-side-down into the Outer Ring and then set the Inner Ring on top of it.  It should take no effort at all to do so, but test the fitment of the two Rings first.

Then drop the Inside Cover into the Inner Ring and set the whole piece onto the Outside Cover.

Optionally add the screws to secure the Outside Cover and fix the Inner Ring.

By the way, the appendages on the Outer Ring are for ½" hook & loop wire ties.

I just happened to have 3 self-attaching ones which work really well.

I've also put adhesive Velcro loop patches on the telescope itself.

This allows me to secure the Telescope Filter Cap to the telescope with the cable ties.

NOTE:

My telescope has an Outer Diameter of almost exactly 5 inches.

This measurement is the actual OUTSIDE of the light-gathering end of the telescope.

See how the Cap is designed to fit over and around the end, but not in.

It will actually fit further down than the photo shows.  I still have the main telescope tube cap on underneath it here, so I've not pushed it on completely.


FILES:

I've uploaded STLs for the 5" version.

These are the STLs I used to print mine using Overture PLA+ in Black.
I printed outer walls first for precision, and used at least 3 walls with ~20% infill.
Layer height was 0.2mm and speed ~40mm/s at 190-200C with a 60-70C heated bed on my Creality Ender 3v2 Neo running MRiscoC Professional Firmware.

I've also included STEP files for all of the parts for you to modify as necessary.

My preferred design tool is OnShape and the fully parametric version of this is available here:

https://cad.onshape.com/documents/24e7a92ffd2ca2ae70299ed2/w/e9eb5da37cba72e365567051/e/a9412cae4fc398fc82274619

Change the OD_Telescope variable to change the whole model.

I've verified configurability down to 1 inch outer diameter:

There's also a Filter Template that you can print to allow you to easily trace out and cut the filter to size.

WARNINGS:

Use only rated solar filter material for viewing the sun.
This is what I've used:

Always put the filter at the light collecting end of the telescope.

Replace any damaged material.  The risk to your eyesight is very real.

Thanks for your interest, and please post any Makes.

Cheers!

&

Always Be Printing