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Upgrade of the McMath-Pierce Solar-Stellar...(1Sep93)
Spectrograph
(from NSO, NOAO Newsletter No. 35, 1 September 1993)

We have completed and reviewed an optical design concept to
cross-disperse the solar-stellar spectrograph at the McMath-Pierce
Facility. The spectrograph now includes conventional gratings and an
echelle grating in a rotatable turret. The echelle grating has been
used in the past, in conjunction with interference filters, to isolate
a single order. By introducing cross-dispersion for the echelle
grating, combined with a large-format CCD array (1024 x 3072), we will
achieve a significant increase in the wavelength range that can be
observed in a single integration.

The optical elements adopted for the cross-dispersion include two
prisms and a removable grism. This configuration essentially yields a
"blue" and a "red" system. The blue system utilizes the two prisms
alone to achieve generous order separation and good efficiency. The
addition of the grism defines the red system. Along with the two
prisms, excellent efficiency and adequate order separation are achieved
in the red longward of about 5270 A. The detailed mechanical design is
now being developed for a design review. We expect that this
modification, along with the large-format detector, will be completed
by the end of this calendar year.

Mark Giampapa, Dave Jaksha, Jorge Simmons

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