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Protostar secondary mounts were introduced in 1995 and featured a simpler collimation process by eliminating the rigid ball-and-socket most mounts used at the time. The design was recently upgraded and improvements include:

  • Carbon composite construction. Major components are made of carbon composite which reduces the weight of the spider by up to 50%. The weight is important for a few reasons; for Dobsonian telescopes weight reduction in the spider takes out four to five times as much weight from the counter-weights behind the primary mirror. A lightweight mirror holder has less tendency for the collimation to shift as the scope points from the horizon to zenith. Less mass also means the entire secondary mount will reach thermal equilibrium faster.

  • More compact design. The secondary holder body is more compact which reduces the cantilever distance of the secondary mirror (i.e., the mirror doesn't hang out into space as far).

  • Now available for any mirror size. Protostar can produce secondary mounts for any size secondary mirror. A custom-sized mirror retaining shroud means no more gluing your mirror onto the holder! This was an essential requirement of the new design, as the days of discrete English-sized mirrors are mostly gone.

  • Improved mirror shroud. The mirror retaining shroud is thin carbon composite now. The shroud eliminates the need to glue the mirror to the holder and also covers the exposed edge of the mirror which is a source of scattered light if left uncovered.

  • Smoother collimation. The collimation adjustments have an even smoother feel due to improved metal threads.

  • True 3-point mirror support. The secondary mirror sits on three "hard points" similar to the way a primary mirror is supported.

  • Clutch disk tweaks. The clutch disk now has a guide cover to ensure the collimation screws are seated into the dimples...even in the dark.


For units with the optional anti-dew heater...

  • Improved heater wire management. The wire connecting the spider to the holder is now retractable into the holder body. No more winding the wire around the holder's stem! Extending the wire makes it convenient to connect the micro-plug when the spider and holder are apart. Then the wire is stowed away when the spider and holder are joined together.

  • Heater element. The anti-dew heater is almost twice as efficient, meaning more heat is transferred to the mirror and less to the holder's body. This eliminates visible thermal currents in the optical path, speeds up the heater's response time, and reduces battery demand.


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