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Fe XIV Corona Seen with MAC II (1Dec92)
(from NSO, NOAO Newsletter No. 32, 1 December 1992)

"First-light" images of the Fe XIV solar corona have been obtained with
the Mirror Advanced Coronagraph (MAC) II.  This 15-cm diameter
reflecting coronagraph has been under development at the National Solar
Observatory site at Sacramento Peak, by USAF/PL/GPSS, NSO/SP, and the
Paris Institut d'Astrophysique sponsored by the French CNRS. This
unique instrument is the first research-grade, ground-based coronagraph
using a mirror instead of a lens as the primary imaging optic to obtain
images of the two-million-degree solar corona. The only previous images
were obtained by the MAC I, also developed by the same consortium. On 9
September 1992, as an active region went over the West limb near 10
degrees South, a flare occurred at approximately 1519 UT. The MAC II,
equipped with a Lyot filter tuned to Fe XIV 530.3 nm and a Videk CCD
camera, began to record data at this time.  Images were obtained from
1519 to 1827 UT with a 5-second exposure time. Off- band images were
subtracted from the on-band images to remove non-coronal artifacts. The
images show evolution in the corona over the active region at 1519,
1739 and 1827 UT. The structure obtained in the images was verified by
comparison with an image obtained with the NSO/SP and PL/GPSS
Emission-Line Coronal Photometer at 1411 UT.

The MAC II will continue to be tested and modified to optimize its
design, which will provide valuable information on critical aspects of
the design of reflecting coronagraphs, which will be incorporated in
the 55-cm diameter MAC III.

Serge Koutchmy, Ray Smartt, Dick Altrock,
Roy Coulter, Craig Gullixson, Jean-P. Zimmerman

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