Economics of restoration

It's difficult to justify the cost of restoring old telescopes. Especially when they are old homebuilt telescopes. If they are large and have an old mirror in them they might require recoating or in the case of the telescopes from HJRO that were disposed of, re-polishing or re-figuring.

In the case of the f5 8 inch it could take a lot of work to republish the mirror, this would involve building a tool and setting up a pitch lap to match the telescope. Removing the old coating and then setting up a stand and test equipment to do measurements. Polishing a mirror is the most difficult and precise step in making a mirror. The pitch lap is sitting on the mirror with a type of polish that is almost like maple syrup in consistency. It's a fine polishing compound that is more like syrup than fine grit that is in a water when you are grinding the mirror. The mirror moves stiffly on the polishing tool which sits below the mirror. The fine grain or more like lack of grain in the polishing compound makes it difficult to push and pull the mirror in strokes as it's moved and sits on the mirror tool or pitch lap on the mirror tool.


A mirror tool normally is created when the mirror is build, a matching piece of glass that is the opposite shape of the mirror and has a convex curve that matches the concave shape of the mirrors surface.

The pushing and pulling of the mirror over e tool takes it's toll on the backs of those working to finish the mirror. Many mirror builders when they get older and have more money have said to me, "mirror building doesn't require much brains, but you need a strong back.". I can testify to this when we build mirrors back on the 1970s.

So what does it cost if you get a professional to fix the mirror. I got a quote from a premium mirror builder to get an idea what it would cost to restore the mirrors that were in the two telescopes in HJRO.

The old 12 inch would cost about $1000. The old 8 inch mirror $600. This does not include aluminizing the mirror, which is an additional expense.

Now let's consider the other expenses to fix the 12 inch and get it up and running. The tube was pretty heavy, it's large and rathr long at 9th in length. It would require a mount that was heavy and well build a permanent pier, a large cover over it, likely another observatory dome. And it would be a narrow field of view instrument. It's f7.17 in focal length. It was close to perfect and would likely cost close to $1500 to restore the mirror.

The mount would have to hold a huge telescope and you'd need a big ladder.

The mount would run $5000 or more. The ladder might cost $600. So we are in the $7000 range to restore the telescope without building an observatory.

I have found memories of the telescope, but I don't have an extra $7,000 laying around to restore this old telescope.

Now consider that a member of the club has a 12 inch f5 reflector, a MEADE light bridge Newtonian truss telescope for $600. This is a used telescope and has an f5 focal length. That's a lot wider field of view and it's a Dobsonian telescope. I have no doubt the mirror on the old telescope is better for viewing planets than the light bridge, but the light bridge is portable and it's less than the cost of starting to fix the mirror in the smaller 8 inch Newtonian.

There are a lot of good telescopes out there already build and also in the usd market. This is why many won't build telescopes today or fix old telescopes.

It's a lot easier to buy a new one.

Sometimes old telescopes end up in a museum or showcase in a large observatory display. We don't have room in the Lincoln Park museum for that huge 12 inch tube. It's old and looks beat up. It's large and to stand it up on end means it can be tipped over. It's rather large to hang from a ceiling. This is why old tubes often end up in the trash.

I squirreled away the old tube at a friends garage. But he's run out of room. The telescope has no practical value, so today it's going to finally be disposed of.


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