Spectrograph fiber cartridge and common corrector mount

The Sloan Digital Sky Survey plug-plate cartridge plugs into a socket on the back of the 2.5-m telescope. In that position, the images of galaxies and other targets fall upon the ends of optical fibers that are plugged into holes drilled in an aluminum plug-plate. The fibers carry the light from these targets to a pair of spectrograph slit-head assemblies that plug into spectrographs. A cartridge consists of plug-plate clamping rings, 32 fiber harnesses each containing 20 fibers, and two slit-head assemblies located on either side of the cartridge.

These images were taken during a SDSS Installation Task Force meeting on February 14, 1997. In the left image, Tom Nash, Don York and Jeff Pier (l to r) inspect a cartridge. A hand-operated lift truck (red) allows the cartridge to be adjusted to a convenient height for assembly. The cartridge is in this orientation (with the plug-plate up) during cartridge exchange. A plug-plate is visible. It was drilled for a field of astrometric standard stars using data supplied by the US Naval Observatory. In the right image, Bruce Margon, Craig Hogan and Don York (l to r) discuss one of the slit-head assemblies. The cartridge has been flipped so that the plug-plate is on the bottom. The plug-plates will be plugged in this orientation.

The left image shows the relationship of the slit-head (l) to the cartridge. The plug-plate is clamped between two bending rings. The bevelled edge of one ring is visible above the plug-plate. The central post contrains the center of the plug-plate to match the telescope surface of best focus. The right image is a closeup of the central post and the plug-plate. The optical fibers are protected by the red nylon tubing.

In the left image, Patrick Waddell (left) explains the assembly of the spectrographic slit-plate to Paul Mantsch. The curved template, bolted to the front of the slit-plate, serves as a guide for the front edge of the fiber harness v-groove blocks during assembly. In the right image, Pat Waddell and Paul Mantsch look at a fiber harness while French Leger looks on. The harnesses for one cartridge are in the boxes stacked behind Patrick.

The common corrector (blue) is located near the front surface of the primary mirror. The fused silica common corrector is 32.5 inches in diameter and is 0.47 inches thick. In combination with the camera corrector (just above the telescope focal surface at the bottom of the Figure), it greatly reduces telescope astigmatism and minimizes field distortion. The common corrector is supported by the common corrector mount (red). Also shown are the primary mirror (blue), the primary support structure (black) and the primary mirror lifting fixture (magenta). The instrument rotator that supports the common corrector mounting and the camera structure are omitted for clarity.

In the left image, Ed Mannery (right) explains the purpose of the common corrector retaining ring to Don York. In the right image, the common corrector cover and the common corrector base are on the top shelf of the cart. On the bottom shelf is the common correcter mount.

Date created: 02/20/97
Last modified: 02/20/97
Copyright © 1997, Walter A. Siegmund
Walter A. Siegmund