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NSO Observations of the 10 May Annular Eclipse...(1Sep94)
of the Sun
(from NOAO HIGHLIGHTS!, NOAO Newsletter No. 39, 1 September 1994)

                               Sac Peak

Several groups had very successful runs at the Vacuum Tower Telescope (VTT)
and Hilltop Lab.  There were intermittent clouds throughout the eclipse, but
there was enough clear sky so that the various experiments could be carried
out successfully.  There was a large crowd of tourists - estimated between
250 and 300 - who gathered for the event, as well as many reporters.   Keil
and Simon from the Air Force group at Sac Peak gave public lectures in
connection with the eclipse.


                            [Figure not included]

     Figure 1.  Phases of the 10 May 1994 eclipse as seen by an H-alpha
     patrol telescope at the National Solar Observatory on
     Sacramento Peak, assembled by Craig Gullixson.

Experiments included the measurement of UV radiation from the Sun and the sky
throughout the eclipse by a group from Phillips Lab.  Vector magnetograms
were obtained at the Hilltop Lab throughout the eclipse.  Keil,
Balasubramaniam, Smaldone (Univ. of Naples) and Rimmele (Kiepenheuer Inst.)
obtained excellent spectral and white-light images of the lunar limb at
various heliocentric positions on the solar disc.  Despite passing clouds
that interrupted the experiments, images were obtained during about 70% of
the available time during the first half of the eclipse with the narrow band
filter at the VTT.  Komm and Mattig (Kiepenheuer Inst., Freiburg, Germany)
obtained center-to-limb observations with the echelle spectrograph at the VTT
during the second half of the eclipse.  These observations were aimed at
determining vertical and horizontal velocity and intensity/temperature
fluctuations as a function of height in the solar photosphere.  The lunar
limb will be used to derive the point-spread function to correct for
scattered light.

                               Kitt Peak

Alan Clark (Univ. of Calgary), in collaboration with a team of NSO staff:
Hartmann, Jaksha, Lindsey, Livingston, Plymate, and Rabin, with REU summer
student Shella Keilholz (Univ. of Missouri) assisting with data analysis,
used the McMath-Pierce Solar Telescope to obtain high-resolution spectral
limb profiles of infrared lines of CO and H.  It is not known how CO can
exist at the high temperatures found in the solar atmosphere.  These
observations were designed to study the vertical distribution of CO as an aid
in determining how the CO is cooled.  Even though the eclipse was not quite
annular at Kitt Peak, these observations used the distant "knife-edge" of the
lunar limb to circumvent the usual limitations on angular resolution dictated
by seeing and telescope diffraction.  In spite of some clouds during the
eclipse, observations show a vertical resolution of about 0.1", about 10
times better than is possible with direct observations.  Preliminary analysis
of  the observations shows the distribution of emission from CO molecules in
the chromosphere to be sharply limited to heights low in the chromosphere.


                         [Figure not included]

    Figure 2.  Solar limb profiles determined from the nearly
    annular solar eclipse of 10 May 1994 from the McMath-Pierce
    Solar Telescope.  The top panel shows the profile of the
    continuum at 4.67 um.  Proceeding downward, profiles are
    plotted for ^12/CO, ^13/CO, and (bottom) for the Pfund-beta
    line of hydrogen.


Jacques M. Beckers

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