Introduction: Off-Axis Mask for Explore Scientific 10" Hybrid Dobsonian Telescope and Solar Filter

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About: Amateur tinkerer addicted to designing and building things.

This off-axis mask is designed for an Explore Scientific ES10 Hybrid Dobsonian telescope. The port is a nominal 4” diameter positioned to allow an unobstructed pathway past the secondary. The port can use an insert to hold a solar filter cell as well.

With the large diameter the mask is printed in quadrants which are then bonded to a support strip with cyanoacrylate glue. The mask is then covered with a 2mm PVA foam sheet to act as an insulator from solar heating as well as a second light blocker on top of the mask itself.

The mask is then attached to a 3d printed collar to secure it to avoid any movement when viewing. Spacers are used to ensure it stays level without bowing when secured over the rim of the secondary assembly.

A cell to install in the port allows for quick pressure fit assembly of the solar cell, or whatever medium you may be using for other non-solar viewing.

All the files for this are available here:

https://cults3d.com/en/3d-model/gadget/explore-scientific-es10-hybrid-dobsonian-off-axis-mask

https://cults3d.com/en/3d-model/gadget/4-grommet

Supplies

You will need the following for this project:


Endcap ES10 V2 quad- thin x3

Port x1

Solar cap seam support V2 x1

Support tabs X4

2 mm PVA sheet


ES10 mount ring- Solar cap Quadrant X4

#10-24x3/4” Machine Screws and nuts X4

#10-24x2” Machine Screws and nuts X4

24mm standoffs X4


4 inch grommet V21 x1

Grommet nut v21

Round filter base x1


Round ring Cap x2 ( to sandwich the solar film between)

Step 1: Mount Ring

Print the 4 pieces of the mount ring. Use a the #10-24x3/4” Machine Screws and nuts to connect 2 of the ring segments together. Repeat for the remaining 2 segments. Place the 2 assemblies at the top of the secondary holder and attach together with the remaining screws and nuts.

Step 2: Mask Assembly

After printing the 3 pieces of mask and the port section, they will be joined with CA glue using the Solar Cap Seam support and the supprot tabs. They should fit snugly but easily without creating a gap between the quandrant edges. Some fine sanding may be required to get his to fit snugly.

After the parts are bonded, a covering of white PVA faom can be applied with spray adhesive to create a thermal abrrier to reduce the chance of deformation from solar heating.

Step 3: Filter Holder Assembly

Print the grommet, grommet nut and filter base. These will be inserted into the port to allow for the placement of the solar filter.

I used Thousand Oaks Optical Solarlite film for this application, but use the material of your choice.

The round ring caps will sandwich the filter material and the perimeter of the part with EVA foam to make a snug pressure fit for the cell into the filter base.