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| The Twilight Compass used by SAS trans-arctic flights resided in the nose of the DC-8. He states that it was used for "correction of the gyro-compass when flying over the polar regions where the magnetic compass is unreliable. It was accurate to half a degree and its use was optimal when the sun was from 30 degrees above to 7 degrees below the horizon." It made use of a "polaroid filter to analyse the polarized light streaming down from the zenith."Solstenen, Primitiv Navigation i Norden før Kompasset..p.86 and 90). Photo and diagram: Thorkild Ramskou, as noted. | |