Pre-1970 Objective with Large Air Space

Hi Folks,

We're trying to figure out the source of a 4" f/15 objective in a pre-1970 telescope. The exact vintage is unknown, but it was bought used around 1969.

The objective has a very large air space, about one inch. The spacer is a thin walled brass cylinder. The cell looks professional, with a nice push pull set up.

I should have some photos soon, but figured I'd start by asking if anyone was familiar with sny objective with such a large air space.

Thanks, and clear skies, Alan

Here's a view of the push-pull screw arrangement on the front of the tube, with the lens and cell removed.

Clear skies, Alan

Attached Image:

Here's the cell with the retaining ring removed. The cap at the base of the photo (top of cell) is not part of the original cell, but was added later.

The black cylinder you can see inside the cell is the spacer between the elements.

Clear skies, Alan

Attached Image: