Author name code: vrabec
ADS astronomy entries on 2022-09-14
author:"Vrabec, Dale" 
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Title: Relationships Between MMF Trajectories and Sunspot Penumbral
    Filament Structure
Authors: Vrabec, D.; Chapman, Gary A.
Bibcode: 1974BAAS....6T.296V
Altcode:
  No abstract at ADS

Title: Streaming Magnetic Features Near Sunspots
Authors: Vrabec, D.
Bibcode: 1974IAUS...56..201V
Altcode:
  No abstract at ADS

Title: Magnetic Fields Spectroheliograms from the San Fernando
    Observatory
Authors: Vrabec, D.
Bibcode: 1971IAUS...43..329V
Altcode:
  No abstract at ADS

Title: Preliminary Magnetic-Field Spectroheliogram Data from San
    Fernando Observatory.
Authors: Vrabec, Dale
Bibcode: 1970BAAS....2..352V
Altcode:
  No abstract at ADS

Title: A New Solar Observatory in California
Authors: Mayfield, E. B.; Vrabec, D.; Rogers, E.; Janssens, T.;
   Becker, R. A.
Bibcode: 1969S&T....37..208M
Altcode:
  No abstract at ADS

Title: A 61-cm Aperture Evacuated Solar Telescope and
    Spectroheliograph.
Authors: Vrabec, Dale; Rogers, Ernest H.
Bibcode: 1968AJS....73R..81V
Altcode:
  A 61-cm aperture, f/20 reflecting solar telescope and associated
  spectroheliograph are currently under construction for the Aerospace
  Solar Observatory. The telescope configuration is Cassegrain, with
  3X relay to a coude' focus by an elliptical tertiary mirror, four
  flats and a field lens. The mounting is asymmetrical equatorial,
  and the telescope tube also functions as a spar for mounting
  auxiliary instrumentation. All mirrors are Cer-Vit. An entrance
  window and the field lens seal off the internal optical path which is
  evacuated. The primary solar image scale is 60 microns/sec of arc. The
  spectroheliograph is an f/20, single pass, Littrow type of 300 cm focal
  length. Dispersion is produced by any one of three turret-mounted 250X
  150 mm plane reflectance gratings, providing three different blazes. A
  slightly telephoto triplet lens functions as collimator and camera. The
  spectroheliograph has two identical exit slits, permitting two 70 mm
  cine film frames to be exposed simultaneously. Subsequent photographic
  subtraction of each image pair produces a time-lapse film record of
  either Zeeman or Doppler fields. The necessary compensation of spectrum
  line curvature is accomplished by curving the entrance and two exit
  slits an identical and fixed amount, and incorporating an adjustable
  two-lens spectrum line curvature compensating system. Scanning is
  accomplished by pivoting the optical portion of the spectroheliograph
  as a unit about a horizontal axis located beneath the grating, parallel
  to the slits and equidistant from them. The field lens placed 20 cm
  above the entrance slit images the telescope exit pupil on the pivoting
  axis. During scanning, the solar image and camera are fixed. Normally,
  a servo driven, water-cooled field stop at the Cassegrain focus is
  activated, which limits the instantaneous telescope field to a narrow
  strip centered on the entrance slit.

Title: Sixty-Two Hour (Continuous) Solar Movie for the Study of
    Supergranules.
Authors: Janssens, Thomas J.; Rogers, Ernest H.; Vrabec, Dale
Bibcode: 1967AJ.....72Q.806J
Altcode:
  In order to study the time changes of slowly varying supergranules an
  Ha telescope was set up above the arctic circle at Thule, Greenland,
  where continuous movies were made of the Ha network taking advantage
  of the "midnight sun. "Installation of the telescope and the observing
  conditions experienced are described. Surprisingly, these included
  extended periods of excellent seeing. The photographs were taken
  at intervals of 3 sec at Hat 0.6 A of a quiet region on the sun's
  equator. Due to solar rotation, the guiding had to be adjusted every
  12 h. The data record of the 62 h period of observing consists of
  about 70 000 frames, from which certain frames are selected to obtain
  movies of various lengths. Three interesting phenomena which are
  presented are very fast periodic spiculelike absorption features in
  the absorption network, coherent waves of velocity patterns seen in
  areas between the network, and the very slow changes in the pattern of
  the network and the cells. At the time of this writing a quantitative
  study is not complete, but well under way. A detailed study of many
  interesting phenomena will have to await construction of a high-speed
  computeroriented microdensitometer. This work was conducted under
  U. S. Air Force Space Systems Division Contract AF04 (695) - 1001.