Thursday, May 7, 2009

Hale Prototype

Back in 1935 Captain Clyde S. "Sandy" McDowell, who was managed the Palomar project for a time, decided that a working 1/10 scale model of the 200-inch telescope was necessary. He wanted it as an engineering model for the big scope that was to follow. It was too small to have a working prime focus cage, but the prototype included nearly every other detail (such as working oil bearings) that the final working 200-inch telescope was to include.

They bought one of the 20-inch scaled down replica versions of the 200-inch mirror from Corning and set about to build their prototype.

Here is the support structure, including the horseshoe for the prototype.

The telescope tube:

Captain "Sandy" McDowell with the completed prototype:

Note the piping for the north and south oil bearings.

The Hale Prototype had been mounted into a dome on top of the Robinson Astrophysics Building on the Caltech campus. There it was use for years by Caltech astronomy students. It was eventually traded to Corning Community College, where it forms a centerpiece to their Eileen Collins Observatory.

Last November I had the pleasure to visit Corning, NY and had the chance to finally see the 20-inch telescope.

The weather was about what you expect in western NY for November: cloudy, but I was all smiles at finally seeing this piece of Palomar history.

The prototype & its horseshoe:

One surprise that I didn't expect was seeing the old control panel for the telescope:

The old control panel isn't used, like Palomar they are using computers to operate their telescopes, but it looks very much like some old control panels I have seen on the mountain.

I am glad that this telescope did not succumb to the ravages of time, but I confess that I would really love to have it here on Palomar for use with our public outreach programs. On the other hand Corning is the birthplace of the 200-inch mirror and this prototype, and the good people who operate it, serve as ambassadors for Palomar and all of astronomy. Of course if Corning ever decides to get rid of the telescope my number is in the book.


Anonymous said...

Hey, why should California have it all? Leave some for us on the right side of the map. :^)

Scott Kardel said...

Well the right side of the map does have it, so all is well.

Paul said...

Thanks for the great follow-up on the mini-Hale. Those construction photos are awesome. I'm excited to finally know the story of that scope and hope to see it some day.

In a previous post you described the wooden model Russell Porter built in '36. Do you have any info on Porter's involvement with design and construction of the Corning telescope? I know this isn't a Porter blog but it's interesting to note that Porter patented his "garden telescope" design in 1922, a design that holds clear roots for the split-ring horseshoe mount of the Hale.

Do you know of any other observatory-class telescopes which used the horseshoe mount design prior to the Hale?

Scott Kardel said...

Hi Paul,

The horseshoe mount and the oil bearing were first designed for the 200" and first put into use with this 20" prototype.

Francis Pease & Russell Porter first put roller bearings into their drawings of the horseshoe, although their calculations showed that it wouldn't work.

McDowell had brought the idea of an oil bearing from the Navy, but it took Guenther Froebel, a Westinghouse Engineer, and Rein Kroon, also from Westinghouse but assigned to Caltech, to make it happen. Kroon worked out what was needed and took some plans to the Caltech machine shop to work out a demonstration for everyone who was skeptical at Caltech.

From TPM: "The test model was a three-foot-square steel slab, six-inches thick, loaded with lead weights to a total weight of 12,000 pounds. ...... At the optimum setting, the weight oscillated freely from one side to the other, almost frictionless."

Kroon had convinced everyone and went on and designed the oil bearings for the 200".

Lory Shepherd said...

Dear Scott,
Thank you for the information. I am Captain McDowell's granddaughter and am always looking for more information on him. Have you read "The Glass Giant"? I am lucky enough to own a copy. They are in high demand in our family!
Lory Shepherd

Scott Kardel said...

Hi Lory,

It is great hearing from you. I may have some more photos of your grandfather. If you are looking for something feel free to contact me.

- Scott