By Request – Photos of The Corning Glass Created 200″ Palomar Observatory Disc

Hi everyone, here is a bonus posting!

I’ve had a request to post the photos, in the library’s local history collection, showing the 200” glass disc made by Corning Glass Works for the Palomar Observatory in 1934.

The disc is officially titled “Palomar Observatory’s Telescope Mirror Blank*”, and is one of the largest pieces of glass ever cast. The glass disc was commissioned by astronomer George Hale in the 1930s. Hale wanted a larger reflecting blank to be installed in the telescope at the Palomar Observatory in California. The Palomar Observatory had been using a 60” disc which, at the time it was cast, was cutting edge technology being the largest piece of cast glass ever created. Hale wanted a better, larger view of the stars which would require a larger reflecting disc, so he commissioned the 200” disc from Corning Glass Works.*

The disc was cast twice and the second time was the charm as a perfect disc was created.

In 1948 the disc was taken by train from Corning to California and installed in the Palomar Observatory where it is still in use today!

So here are the few cool photos of the disc we have in our collection!


Linda Reimer, SSL



*200” Disc, Corning Museum of Glass,


If you’d like to know more about the creation of the disc, check out this page on the Corning Museum of Glass site:


And if you want to dig deep on the subject, here is a link to an excellent Rakow Research Library LibGuide on the subject:


And if you’d like to read a book about the disc, and the Palomar Observatory, here’s a book you can request from the library:

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