the improvement of telescopes and apparatus, [121].
the relative brightness of the stars; variable stars, [130].
researches on double stars, [134].
researches on planets and satellites, [140].
researches on the nature of the sun, [145], [186], [198].
the motion of the solar system in space, [149].
researches on the construction of the heavens, [154].
scale of celestial measures; distances of the stars, [170].
researches on light, heat, etc., [176].
researches on the dimensions of the stars, [193].