Conical Baffle Mandrel

The Sloan Digital Sky Survey 2.5-m telescope has a uniquely large 3° field of view. The novel two-mirror optical design achieves zero distortion in the imaging mode using two transmitting correcting elements. However, to avoid excessive central obscuration, a conical baffle is necessary in addition to the usual primary and secondary baffles. This conical baffle is suspended approximately midway between the primary and secondary mirrors. It is to be formed of graphite fiber reinforced plastic because of the high stiffness to weight ratio of this material. The geometry of the part must be well-controlled. Consequently, it will be formed on a machined aluminum mandrel.

The conical baffle mandrel was machined by Machinists, Inc. (Seattle, WA) the week of 15 December 1996. It was inspected on 23 December.

The mandrel was turned on this 2.1 m (84 inch) vertical lathe at 120 RPM. In the left image, John Galbraith and Al Diss discuss the part. In the middle and right image, "Big Ed" operates the lathe.

Grooves are machined in the outer surface of the mandrel. These result in ridges on the inside of the graphite fiber reinforced plastic that is formed on this surface. These ridges interrupt grazing scattering paths that would otherwise exist on this surface.

Date created: 12/23/96
Last modified: 03/08/97
Copyright © 1996, Walter A. Siegmund
Walter A. Siegmund