1962 Cave Astrola 8 Inch f/8 Newtonian Reflector Model "B" Deluxe

(text copied and pasted from a post I made to Jeff Houston's Cave Astrola discussion forum)

The scope is an 8" f/8 Cave Astrola Newtonian with a coating date of 12-12-62. We bought it in 1996 for $465 from a lady who had forgot she had it stored in her closet for more than 20 years. This was the first telescope my wife and I ever owned. The mount had been stored outside in a covered carport with a canvas cloth over it. It was in excellent mechanical shape (RA driven) but the paint was a lost cause. The OTA was in great shape. The only thing I could find wrong with it was that the tube was slightly egg shaped because it had been stored on its side for 20 plus years. I assume that blankets or clothing must have been piled on top of it. Even with this slightly eggshaped tube the rotating rings still work fine.

The primary coating looked ok but was dirty. After soaking and rinsing for an hour or so I gently drug the first cotton ball across it. To my shock, the cotton ball just shredded. Not knowing anything about star testing I sent the mirrors out to QSP for new coatings. It never occurred to me to look at the sides of the mirror for a signature but there are no markings on the back of the primary. I doubt that this was an Alika Herring mirror since he had left Cave to work for JPL about 14 months earlier. Next time I remove the primary for cleaning I will have a good look for markings.

While the mirrors were out I quickly built a very crude and HEAVY dob mount for the OTA. Three weeks later the scope was reassembled, collimated and used for the first time. I was immediately disappointed with the images due to vibration. You could not even touch the focuser. I ruled out the mounting as the cause and realized that the secondary/spider was the culprit. The distance from the secondary to the central hub of the spider was over 4" and the slightest touch would set it in motion for a minute or more. Correcting the problem would require drilling holes in that beautiful white tube and I wanted to avoid that.

The only other problem I found with the OTA was the focuser. It was butter smooth with no slop at all but the eye lens of most eyepieces was over 4" from the surface of the OTA. The focuser had a slip fit extension tube in it that had to be pulled way out to achieve focus. I noticed that the drawtube was sagging under the weight of the eyepieces causing me to look above the secondary as viewed through the focuser. To top it all off the focuser drawtube was very nicely chromed on the inside!

After some thought and talking over my options with the fine people (including Rick Singmaster) in the #ATM IRC chat room and my local ATM group, I decided to install a new 3 vane Protostar diagonal/secondary holder as well as a JMI mini-3 focuser. In order to reduce the focuser height to accommodate the new JMI focuser I had to either move the primary down the tube or the secondary and focuser up the tube. Moving the primary would only gain ¼" of the needed adjustment and in my mind that did not justify drilling three news holes for the primary cell. A little more calculating showed that I could just barely avoid drilling holes in the upper aluminum end ring to accommodate the new spider. In the pictures you can see that I had to make some small aluminum spacers for the spider vane bolts since they would rest half on and half off the tube end ring. A small light shield (not pictured) that extends one inch past the end of the tube opposite the focuser prevents stray light from
entering the focuser drawtube on the inside.

Small holes in fiberglass are easy to repair or hide but large focuser sized holes are a different animal. So, with great trepidation I chucked up my trusty hole saw and triple checked the location of the hole for the tenth time then gently went to work. With the scope assembled, my 40mm TV plossl ep in place and a clear sky I was very relieved to find focus with a 1/16" out travel left to spare! I didn't screw it up! It turned out that the round plug I had cut fit the original focuser hole so perfectly that it held itself in place. When I installed the Telrad, the base perfectly hid the original hole so I put the plug away for safekeeping. The original focuser hole can be seen in the 5th picture down the page. To aid in aligning the focuser with the optical axis of the OTA I used a JMI backing plate between the tube and focuser. This allowed me to use the four leveling setscrews on
the focuser without them digging into the tube. The backing plate is covered with thin felt to protect the tube.

Since the original paint on the mount was just about gone I decided to bead blast the aluminum parts and paint it royal blue. This allowed me to take the mount apart to clean and lubricate everything. While inspecting the worm and ring gears I could not detect the slightest hint that they had ever been used. There were no smooth wear marks on the gears and the grease was all still very transparent. Because of its bulk, weight and "back corner" storage location I have never even used the GEM. It was also difficult to convert its dob mounting quickly for EQ use. With the new dob mount altitude bearings I've built, conversion from dob to EQ use will be less than a minute. My spray can paint job was adequate but I want to have it powder coated some day. Now all I need to do is build an enclosure for the mount in my yard.

The new dob mount was built in an unheated/freezing garage in January of this year. It's made of ½" (9/16" actually) Baltic Birch plywood stained with cherry stain and finished with Helmsman Spar Urethane. The biggest complaint my wife had about the original mount I built was it's weight and when I saw found this design in a post to the ATM list I instantly knew this would accomplish every need we had for the scope. The altitude bearing design let's us take full advantage of the famous Cave rotating rings in both dob and EQ mount configurations.

In 1998 I gave my wife an Orion Sky Wizard III for Christmas but I had to build a new rocker box for the old dob mount in order to use it. I never got "a round tuit" so the SW3 sat in the closet until this mount was built. We finally got a clear dark sky weekend and I was amazed at just how well the SW works. Even with a less than perfect alignment, objects are very near the center FOV with a 26mm TV Plossl. There was no noticeable drop off in pointing accuracy after two hours of hopping all over the sky.

The optics in this scope are good as any I've ever seen. Planetary performance borders on exquisite with deep sky performance limited only by atmospheric conditions. Cool down times seem to be about 30 minutes. We point the bottom of the OTA into any breeze that might be blowing and this seems to help. Stability, even at high power is very good. Now the only complaint my wife has is that the EP is too high when pointed near the zenith. I might trade her straight across for a very fine 8" f/6 Richard Fagin dob I have if she complains about it again. :o)

We have saved all the original parts in case we ever decide to restore it to original. I have dreams of one day (when we're very old) giving this scope away to some young amateur who will truly appreciate just what a fine instrument it is. Thousands of men, women and children have had their first look at the Universe though this scope and we hope that thousands more will as well.