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Available for Cassegrain secondary mirror sizes from 1.30" to 8.0" diameter.
Carbon composite mirror retaining shroud fits your mirror perfectly without glues.
Sturdy 4-vane spider design.
Unique simplified collimation procedure.
Larger models feature heavy-duty vane design.
Made from corrosion-proof materials.

The Protostar Cassegrain mounts accept any mirror size from 1.30” to 8.00” diameter. The mirror rests on three "hard points" similar to the support for your primary mirror, and a custom-sized mirror shroud retains the mirror without the need for glues. Collimation adjustment uses the same simplified principal as our Newtonian mounts.

Since some Cassegrain telescopes require precise spacing between the primary and secondary mirror. You can adjust the axial position (i.e., closer or further from the primary) of your secondary mirror with high precision. Made in the U.S.A.

Each kit includes:

spider assy

mirror holder assy

mounting hardware


Read how to order secondary mounts...

Detailed Product Images
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Download the installation manual for Cassegrain secondary mounts.

Prices include both spider and mirror holder.

The tube ID ranges shown in the table are for pricing purposes only, and the spiders are not adjustable over this wide range. We make your spider to fit your exact tube requirements. When ordering, please provide the actual tube (or cage) inside diameter. We will make your spider slightly smaller to permit proper vane tensioning.

The dimensions in the table are in inches.

Note: Spiders are custom-made for your inside diameter (ID), and are not adjustable over the ranges shown in the table below. When ordering, provide the information described on the ordering information page.

Secondary holder size













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