Hello all,
Here some comments from John Briggs and Richard Berry in the Antiqur Telescope Forum:
Hi Denis,
I’m pretty sure it’s a plate holder from a spectrograph. Some old instruments that I have seen had very inclined focal planes like this hardware suggests. One example is the setup used for early Raman spectroscopy. But I think some other types I have seen, but did not have time or circumstances to study, had similarly included plate holders.
All the 2×10-inch plate holders on the old Mount Wilson solar telescope Littrow spectrographs are tiltable to allow for varying focal lengths of the different wavelengths recorded in a given exposure (given that the camera used a lens with some inevitable chromatic aberration). But the maximum angle allowed was not nearly as great as what has been built into the unit you show.
I’ll see if I can find pictures of spectrographs with similar big-angle plate holders to give us a better clue!
–JWB.
And a bit more: These highly inclined plate holders were used on quartz spectrographs for violet and UV light, where the prism and the camera lens, etc., where made of quartz for good UV transmission. In this case, the camera lens might not have been more than a single element, given that the goal was transmission and focusing of UV. Only quartz was possible! Thus, the camera’s focal length was a function of wavelength. And from the appearance of how these things were made (with a big tilt), it was a strong function!
Google “Adam Hilger quartz spectrograph.”
I recently learned that Adam Hilger had been an employee of John Browning in Hilger’s youth. (I’m a big fan of all things Browning!)
–JWB.
Hi all–
I agree. There were similar plateholders on the spectrographs at C.R.E.S.S. at York University (Toronto) where I worked many years ago. The focal surface is inclined if there are refractive optics in the instrument. They would take many spectra on each plate, moving the plate down for each spectrum. If you examine it carefully, you’ll probably find what were called “deckers” that allow the spectroscopist to shoot a 6 to 10mm slice on a 3-1/4 x 4-1/4 plate, or whatever size the plateholders take. I was sometimes able to snatch boxes of out-of-date 103a-E Kodak glass plates before they chucked them out.
–Richard