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
siegmund@astro.washington.edu