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.

He 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 knows I build and restore telescopes for fun.

Stopping by the bike shop this week we loaded the telescope into the vehicle and I hauled it off. Complete with optics the telescope will need some work. Rust and a shattered tube around the mirror cell are the first obvious issues.

Judging by the descriptions and photographs in the 1970 catalog, the telescope is an 8″ Cave Astrola Lightweight Deluxe. This telescope was one of the most popular of the Cave designs and listed at $495 in 1970, or about $3,122 in 2017 dollars when adjusted for inflation.

The mount has now been dismantled, residing in a box as a pile of parts in the garage. Beyond significant rust on the shafts there is no real problem with any of the parts.

Tube Damage
Damage to the optical tube of the 8″ Cave Astrola

I still need to figure out how to dismantle the RA shaft and bearings, if possible. I may end up leaving these together, though the question of the condition of the bearings remains.

Amazingly the motor functions properly, rotating with a nice quiet whirring sound. There is a little rust on the worm, nothing worrisome. The cord will require replacement.

The power switch is unusual, with an NE-2 neon bulb in the switch shaft. The bulb is bad, of course, but I have decided to rebuild the switch just for the authentic look, probably with an LED.

The next nice surprise is the condition of the primary mirror. Once the first layer of mud and crud was washed off the coating proved to be in pretty good shape. No need for a re-coating in the immediate future, not bad for a nearly 40 year old mirror.

Was the primary re-coated somewhere in the intervening years? There is a sticker from a mirror coating company on the back center of the mirror. Pancro Mirrors Inc., 6413 San Fernando Road, Glendale, California. Pancro no longer does aluminization work for telescopes, now focusing on optical products for the motion picture industry.

Mirror Data
The data inscribed on the side of the 8″ mirror

Of course the usual text written into the glass on the side of the mirror gives the provenance… Cave Optical Co. M-783416 – F/6 – 48 5/16″ FL – Apr – 4 – 1978. The telescope was probably constructed about 40 years ago assuming the mirror did not sit on the shelf for too long. The telescope was among the last Astrolas as Cave Optical closed shop in 1980.

In general the telescope will take less work to restore than I feared. The worst will be repairing the optical tube. That will probably require epoxy and maybe a little fiberglass to reinforce the repairs. Sand, patch, and paint will have the OTA back in shape.

I considered installing a drive corrector in the drive unit as I did the C-8 mount, but there is no room for the transformer. Best to keep that part original and use an external inverter if needed.

The focuser is an issue, will look into replacing it with something nicer. I also need to replace the finder, will need to fabricate something that looks good in the original rings, some sort of 8×50 arrangement should do the trick there, not difficult.

There is some fun work ahead!

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on Mauna Kea, Hawai'i.

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