what observations did he make ?
That the Moon is farther from the Earth than the Sun.
Brahmagupta
In chapter seven of his "Brahmasphutasiddhanta", entitled "Lunar Crescent", Brahmagupta rebuts the idea that the Moon is farther from the Earth than the Sun. He does this by explaining the illumination of the Moon by the Sun.
what is the parity of zero? The quality of an integer being even or odd—is even. who invented the number zero? Indian mathematician Brahmagupta is this number an even or odd number? Even number what is the main reason for it being an even number? Zero is an integer multiple of 2, namely so zero is even. during which year was the mathematician born? 598 CE where was he born? Bhillamāla, Gurjaradesa apart from math, what else interested him? Astronomy
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Brahmagupta [SEP] Astronomy
Some of the important contributions made by Brahmagupta in astronomy are his methods for calculating the position of heavenly bodies over time (ephemerides), their rising and setting, conjunctions, and the calculation of solar and lunar eclipses. In chapter seven of his "Brahmasphutasiddhanta", entitled "Lunar Crescent", Brahmagupta rebuts the idea that the Moon is farther from the Earth than the Sun. He does this by explaining the illumination of the Moon by the Sun. 1. If the moon were above the sun, how would the power of waxing and waning, etc., be produced from calculation of the longitude of the moon? The near half would always be bright.