A Photoelectric Photometer for the Fe XIV Solar Corona
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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A photoelectric photometer for the emission line 5303 Fe XIV formed in regions where Te - 2.0 x 10 to the 6th power degrees K of the solar corona is described in this paper. The emission line is isolated from the scattered light of the sky and the instrument by means of a rapid change in the bandpass of a birefringent filter. A piezoelectric variable retarder is used to accomplish the bandpass modification as a 100 kHz rate. The instrument is capable of detecting the corona in scattered light situations that exceed the maximum allowed for filter photography by a factor of 10 thus, the number of hours during which coronal observations can be made with the photoelectric instrument is significantly larger than the photographic method presently used. An example of synoptic observations of the Fe XIV corona is presented. Spatial resolution achieved is limited by the scan stop in the image plane and is 1.1 arc minutes. Scans are made in position angle, holding the scan distance from the limb a constant. The Fe XIV signal is detected out to a distance of 1.55 R Ro above the limb.