Getting a Mirror Re-Coated

The classic Cave Astrola telescope has become my roll-out, quick observing session ‘scope, often found in my driveway. I have also used it a few times at darker sites when I expect the weather to be damp or dewy as a Newtonian is more protected.

The restored 8" f/6 Cave Astrola under a dark sky at Kaʻohe
The restored 8″ f/6 Cave Astrola under a dark sky at Kaʻohe

While the restoration job was finished some time ago, I never got around to re-coating the optics. Meanwhile the telescope has seen good service on many occasions as I enjoyed this fun-to-use instrument.

The optics did need some attention… The primary mirror from the Astrola appeared to have not been re-coated since it was made in 1978. Thus the aluminum coating was over 40 years old. While the coating looked bad, it was still serviceable, producing reasonable images.

Still, the loss of light due to the old aluminum coating was probably reducing the effectiveness of this 8″ telescope to something more like a 6″ telescope. I had meant to get it re-coated some time ago, but we know how these things work.

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Voggy Luna

The vog has been thick, really thick. Even here on the west side of the island it is enough that visibility is limited to a few miles, the mountains and ocean are lost in the haze. With the ongoing eruptions on the other side of the island and a lack of wind the vog has enveloped the entire island in gray. At times you can even smell it, the tang of sulfur in the air.

As the crescent moon set this evening it was reddened by the vog. Washed with a ruby red that was reminiscent of an eclipse. This image has been processed for noise and contrast, while the color was unchanged from the raw image. It really looked like this…

Voggy Luna
The setting crescent moon reddened by volcanic haze.

Restoring the Cave Astrola

I do enjoy a nice project I can work on, get my hands dirty, and use my skills. A classic telescope in need of restoration? Just the thing.

Restored Cave Astrola 8" f/6
A restored Cave Astrola 8″ f/6 Lightweight Deluxe

This telescope was literally rescued from the trash. Matt, the owner of the excellent Mountain Road Cycles in Waimea found the telescope at the transfer station.

Matt put a message into the folks at the observatory, who represent more than a few of his customers. The info was quickly forwarded to me, as everyone here knows I build and restore telescopes for fun.

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Dreaming of a Cave Astrola

Restoring the 8″ Cave Astrola has me again looking at these classic telescopes. Reading the history of Tomas Cave and Cave Optical. Looking at the old advertisements and remembering things long thought forgotten. I may never have owned one before, but the Astrolas still had an impact upon me years ago.

My Astrola is now operational, with final assembly and collimation completed a week ago. So far I have used it for several evening sessions of observing from the driveway. The result is several pages of notes in the observing log, wandering through nebulae, clusters, and binary stars in Orion, Canis Major, and Puppis.

Cave Optical Advertisement 1970
Cave Optical Advertisement 1970, from Phil Harrington
When I was just starting my journey in astronomy the Cave Optical advertisement in each month’s Sky and Telescope was something to inspire dreams in a young teenager. In many ways those dreams have never been forgotten.

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