These discs are used to identify stars which will then have the altitude measured wth a sextant. At sea a sextant is used that references the horizon for the base line. In flight a sextant is used that has a bubble to achieve the horizontal reference. In a non-pressurised aircraft and early pressurised aircraft the starshot was taken in an astrodome. In later aircraft a periscopic sextant is used which you poke out through a fitting in the top of the fuselage. I don't know if all Boeing 727s had this fitting but the 727s operated by Trans Australia Airlines did along with a platform stowed on the bulkhead that clipped to the cockpit floor to stand on when taking the shots. The airline employed a navigator in those days.
The inertial reference system (IRS) made the navigator and all his equipment redundant. GPS even more so. Soon there will be very few people fully conversant with the art of astro navigation.
David
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Hell no! I'm not that old!
Last edited by motto; 23-11-21 at 02:34.
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