The Concorde flew to an altitude of 60,000 ft (18.3 km) where stars should be visible at noon, aren't they? This question asks on how high stars become visible, and it is said Blackbird pilots could see them at 80,000 ft. The Concorde flew at the Armstrong line when highest, above more than 90% of the atmosphere's mass. Are there reports of passengers and pilots on the Concorde seeing stars (other than the Sun) when at peak altitude? Also, did the Sun appear whiter due to the thinner atmosphere?

  • $\begingroup$ You can see Sirius from sea level. Climbing to 18 km doesn't change anything, still only Sirius. "The daylight visibility of stars has been investigated for an observer altitude of 100 000 ft, using published visual threshold data and calculated sky luminance. Venus, Jupiter, and Sirius, plus Mars at its brighter phases, can be detected with the naked eye", source. Sirius has a magnitude of -1.46 at sea level. At night an eye can see down to +6 only. Someone may build an answer starting with these elements. $\endgroup$ – mins Sep 19 '20 at 2:04

Yes, in at least one exceptional circumstance. The book Racing the Moon’s Shadow with Concorde 001 describes a 1973 scientific flight that remained in the moon's umbra for more than an hour, in daytime. As stars are quite visible from the ground during a solar eclipse's totality, they would have been even more visible from a 17 km altitude.

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    $\begingroup$ I don't think the question was asking about a solar eclipse! Even though it's technically "in daytime", the question is clearly about normal daylight. $\endgroup$ – Bianfable Sep 14 '20 at 16:16
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    $\begingroup$ I don't think so, either! But I couldn't resist, that flight was just so cool. $\endgroup$ – Camille Goudeseune Sep 14 '20 at 16:43
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    $\begingroup$ @CamilleGoudeseune Sorry but during a total eclipse you can see them even from the sea level as you say yourself. :-) $\endgroup$ – Giovanni Sep 14 '20 at 16:48

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