Telescope Making – A Darker View

A Simple Helical Crayford Focuser

How simple can a focuser be?

This has been a bit of a design challence for me… Just how small, how simple, can I make a focuser and yet still provide excellent usability. My latest Helix 1-14 design is my best yet.

A simple helical crayford telescope focuser — A simple helical crayford focuser

As my 3D printer design skills improve I applied lessons learned and the unique capabilities of an FDM printer to the problem of a focuser. After a bit of a journey I have arrived at a design I can consider finished. Is it the final design? I may tinker some more, but I am satified for the moment.

The design is based on a few ideas from here and there, products I have seen or used, internet postings from others faced with the same challenge. I am not one for just printing someone else’s design, I rarely do that, I want to do my own, and maybe make it better.

Testing a Mirror

As I have observed lately, most of the small telescope mirrors available right now are out of China, most of those produced by one company, Guan Sheng Optical or GSO. If you want a small mirror, say a 6″ or 8″ mirror, there is not a lot of choice, the mirror makers in the US generally do not do anything smaller than 10″.

A textbook Foucault knife edge test image on a 6″ f/4 mirror

The GSO mirrors range from decent to pretty bad, with no way of knowing what you will get when you order, just luck of the draw.

But how do you tell?

Working on it…

Schematics, notes, and tools scattered beside the work area... — Schematics, notes, and tools scattered beside the work area…

Building More Walls

With the big wall completed along the driveway, and a bit of a break over a hot muggy summer, I am again building walls.

Back Yard Wall Excavation — Excavating for a series of terrace walls in the back yard.

This is not the sort of wall between people, I detest those, but rather a real rock wall, terracing the backyard to make the space available for landscaping and other projects. This puts into action a plan that has been brewing for years.

Part of the impetus is that I have a source of rock secured, a very large pile of very nice rock found in a Waimea backyard. One of my co-workers casually mentioned he needed to rid himself of a pile of rock, to which I quickly asked… How much rock?

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.

Cave Astrola Restored

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

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.

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.

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, 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.

Continue reading “Dreaming of a Cave Astrola”

Telescope Restoration Gallery

Yes, a new/old telescope has arrived at Andrew’s Home for Wayward Telescopes… A beat up and neglected 8″ Cave Astrola. The new arrival has me thinking of the other telescopes that have come through recently…

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The 8″ f/6 Cave Astrola Lightweight Deluxe

Yes, Andrew’s Home for Wayward Telescopes has a new resident, an 8″ f/6 1978 vintage Cave Astrola.

8" Cave Astrola — The 8″ Cave Astrola as it arrived

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

Continue reading “The 8″ f/6 Cave Astrola Lightweight Deluxe”