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Spectroheliograph Fixture on the 13.5-m...(1Sep93)
McMath-Pierce Spectrograph
(from NSO, NOAO Newsletter No. 35, 1 September 1993)

Call it 1900s technology, but when a visitor recently inquired about
imaging Ca K2V with a purity of about 0.05 A, we realized that the
conversion of the old spectroheliograph to a stellar instrument
resulted in a lost capability. The narrowest K-line filter in our
possession has a passband of 1 A.

In response to this need, Keith Pierce has built a moving plate
holder-slit assembly which mounts on the photographic exit port of the
vertical spectrograph. It takes 4 x 5 inch film, typically Kodak
linagraph shellburst. The existing predisperser serves as a prefilter
for order selection. Image motion is provided by the telescope drive.
With the visible-light grating in the sixth order, dispersion is 8
mm/A.  Entrance and exit slits of 0.5 mm required 0.3 seconds per step
to nicely expose K2V. Obviously, a linear array would be useful here.

Bill Livingston, Keith Pierce

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