Strabo Geography 2.5.42

[42] In regions 3800 stadia north of Byzantium the longest day consists of sixteen equinoctial hours; the constellation Cassiopeia being brought within the arctic circle. These regions are situated around [the mouth of] the Dnieper and the southern parts of the Maeotis, at a distance from the equator of 34,100 stadia; and the northern part of the horizon during almost all the summer nights is illuminated by the light of the sun; a certain degree of light continuing from sunset to sunrise. For the summer tropic is distant from the horizon only the half and the twelfth part of a sign ¹ [of the zodiac], and this therefore is the greatest distance of the sun below the horizon at midnight. With us when the sun is at this distance from the horizon before sunrise and after sunset, the atmosphere is enlightened to the east and west respectively. In the winter the sun when at the highest is nine cubits above the horizon. ² These places, according to Eratosthenes, are distant from Meroe rather more than 23,000 stadia, ³ for he says that [from the parallel of Meroe] to the Hellespont ⁴ there are 18,000 stadia, and thence to the Dnieper 5000 more. In regions distant 6300 stadia from Byzantium, and north of the Maeotis, the sun during the winter time is, when highest, six cubits [above the horizon]. The longest day consists of seventeen hours.