Submitted by: Dave Wilson (texasdavew@gmail.com)

A magnetic finder scope mount for the ETX90

I wanted a quickly detachable finder scope for the ETX90 – especially because it is a great grab-and-go telescope and also because leaving the original mount attached leaves it vulnerable to damage. Another goal was to reduce the number of screws needed to align the finder scope and then lock it in place.

Here is the result, with the print specifications following the description.

Description

The mount is designed quickly attach and detach using magnets. It consists of a clamping mechanism that tightens down on a rounded collar that surrounds the finder scope. The collar is split to allow it to expand and slide onto the finder scope and then to compress around it under pressure to hold it securely. The clamp that compresses the collar has a rounded channel that allows the scope to be moved for alignment with the main telescope until the clamp is tightened.

The clamp is hinged and top and bottom are joined with a pin. The clamp is tightened by a knurl cap fitted to 4-40 screw and nut.

The clamp mechanism is connected to the bottom mount using 4 neodymium magnets (5mmx3mm).

Once assembled, the magnetic bottom mount attaches to the ETX90 as usual. Then the clamp fixture slides over that until the magnets “engage” and hold the finder scope in place.

Once the mount is in place, you can loosen the screw and move the finder scope around until it is centered on the same object the telescope is showing, then tightening the screw will hold the finder scope in place.

When packing up, you can easily remove the finder scope and its clamp mount as a single unit and store it away. The remaining lower magnetic mount stays on the scope and is low-profile enough to avoid being torqued in handling causing damage.

The result is simple finder scope adjustment and convenient attachment and detachment.

Build Details

Print Information
- Printer: Davinci Pro 1.0
- Filament: Flashforge Pro 1.75mm ABS Black and Neutral for prototypes - Print Speed: 20mm/sec
- Layer height: 0.2mm
- Extruder temperature: 230 deg C
- Bed temperature: 100 deg C
- Fill density: 30%
- Support density: High

Materials
- Filament: 10 meters (estimate)
- 1 4-40 hex drive screw 12mm long (or longer to avoid inadvertent opening)
- 1 4-40 hex nut
- 1 2mm pin 32mm long
- 4 Neodymium magnets 5mm diameter x 3mm high

Build Tips
- The hex cavity for the 4-40 hex nut is slightly small. The hex nut was placed over the cavity, then heated with a soldering iron and then melted into to cavity. This is holding it in place.
- The cavity of the printed knurled knob for the 4-40 screw head is slightly small. The screw head was heated then melted into the printed knurled cap holding it in place.
- Don’t over-embed the magnets – it’s better that they are able to contact each other for stronger holding power.

Files
I have included seven files for the magnetic mount project that are included in a zip file. Below are their names and descriptions:
- The file that contains all the components for printing them all together:
    o ETX90 finder mag mt All.stl
- The file that contains the top clamp piece only:
    o ETX90 finder mag mt Top Clamp.stl
- The file that contains the bottom clamp piece only:
    o ETX90 finder mag mt Bottom Clamp.stl
- The file that contains the magnetic base only:
    o ETX90 finder mag mt Base.stl
- The file that contains an alternate magnetic base only (has slight blend where it meets the telescope):
    o ETX90 finder mag mt Alt Base.stl
- The file that contains the finder scope collar only:
    o ETX90 finder mag mt Collar.stl
- The file that contains the knurled cap only:
    o ETX90 finder mag mt Knurled Cap.stl

Good luck with your build. If you have any questions – contact me at texasdavew@gmail.com

Click to download the 3D printer STL files (2 MB)

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