Still testing and tweaking. The lens had some astigmatism at high power when I first tested it. I was able, after 8 iterations, to reduce the astigmatism to where I'm finding it hard to see at 635x. I had to rotate the flint element about 100 degrees counterclockwise to the original alignment marks. Strange. The color correction continued to improve with each interation to where I hardly notice at all, in full daylight, on my artificial star test target at high power. Now my curosity is way up as to what type of glass is in this set. It has no where near the secondary color that I was expecting a typical doublet would have at F/10.

Now testing side by side with my 5" refractor. Setting up multiple AirForce high resolution optical test targets. This should prove interesting...

 

Here is the test setup and scopes. Using the distant telephone pole.

 

Just completed making a new collimatable focuser back plate. Thinking about splitting the tube into three components to make this scope easier to live with. Since I will have to set this scope up for use every night, three lighter weight tubes would be better for me in setup. In fact, unless the weather is bad, the whole thing will remain set up minus the end tubes holding the rear cell and the lens. Will brainstorm design later tonight.

I was going to use the massive DOB mount that came with the scope but I'm leaning toward a clock driven EQ mount. I have a large Cave Astrola EQ head and counter weights. I just have to find material for a pier. Having fun

 

Hi Dave,

The focuser in the pic is a 2" Chinese refractor focuser. I'm only modifying the existing scope. The scope was originally white. The astronomer, at the college I got it from, spray painted it black. As you can see in the photo, it looks like it was painted from a can of spray paint. Yeech! Will fix that later after I rework all the knicks, scratches, and gouges on the OTA.

The telescope was manufactured by Thompson Optical Engineering Co. in 1962. There were two such scopes on the tracking platform. They were each mated to two different style cameras. The front element is coated and shows some age effects. It is slightly yellow. This has me wondering about the lens design too.

The color corection is quite good for a F/10 of this size. The scope came with the original blueprints. It looks like they made a 10" F/4, F/6, and F/10 models. The optical design parameters that the college advertised for the scope were for the F/6 model, not the F/10. The rear of the flint element is positive which usually means that the lens is corrected for coma. I can't wait to get it under the stars and planets!

Yes, the scope is a beast! I had to cut off the rear housing so I could make a new one for the Chinese focuser. The original rear housing was made from a 13" diameter 1-1/2" thick solid slab of aluminum. It had a central inner aluminum sleeve that housed a 6" diameter 2" thick steel housing that slid back and forth for focus adjustments. Quite heavy. I'm guessin' this mod droped 25lbs from the OTA.

 

Whew! Got the scope up and mounted. I'm gettin' too old for these kinds of antics Anyway, Jupiter was well seen at 240x. Lots of details. The moons were showing disks of differing sizes despite the 5/10 seeing. The color correction is very good. I was again surprised. Jupiter had a faint tight halo that was less than my 5" F/9 refractor. This is not a standard achromat. I'm guessing that the slightly yellow crown element is in fact a lanthanum lens. A 10" achromat at F/10 should have much more color. I pushed the lens to 420x on Jupiter trying to get the color to be more obvious but to my surprise it was less. My guess was a more precise focus. Saturn revealed all the usual details. The image was seeing limited. Altair revealed above average color correction as well.

250lpi glass ronchi revealed good spherical correction and a clean edge. Seeing was not good enough for critical star testing.

The DOB mount in the pic is a massive beast. Heavy, and a lot to move around. Buttery smooth motions? NOT!

 

This lens is over 50 years old (1962).

 

Tube now split into more easier to manage components. The end tubes will be removable with hand knobs. Since I can't afford an observatory yet, this will make the refractor much more managable when I set it up. Hope to clean up the ends and "tie" the tubes together tomorrow. My even take the beast up to the local astro summer hot spot for a run when it's all detailed out (Mt Pinos) Maybe the local refractor guys will let me hang out with them

 

The whole scope, Cave GEM included, should easily fit into my motorhome. The pic shows the tube couplers that I just finished. Long day. I might get them installed this evening.

 

Well... I got half of the tube couplers installed. Hope to get back at it tomorrow. The removal of the tube ends reduces the main tube to just over 5ft long and also reduces the main tube weight by quite a bit. The tube spacing and holes are for cooling. Just like my former 8" refractors, there is a lot of glass to cool. Imagine having a 10" reflector with two primary mirrors back to back instead of one The lens has a .125" spacer ring. The "air" between the lenses can sometimes develop a heat bubble that appears in the out of focus diffraction pattern. I remember having a wide air space 6" F/15 that did that. This heat bubble puts a flair on stars. These mods should minimize or eliminate this affect. Fingers crossed.