Having sexual intercourse with one's wife at the time of Fajr Prayer thinking that it was Tahajjud

Q 1: A man slept beside his wife after eating Suhur (pre-dawn meal before the Fast) in Ramadan and he was confused concerning the loud recitation of the Imam (leader in congregational Prayer) in the mosque. He thought that it was Tahajjud (optional late night Prayer) and did not try to find out whether it was the Fajr (Dawn) Prayer or the Tahajjud Prayer, and he finally copulated with his wife. Surely, this man was able to turn on the light to know the time but he did not. However, after he had sex, he found out that it was the Fajr Prayer. By doing so, is he regarded as careless with and degrading the prohibitions of Allah? (Part No. 9; Page No. 253

A: If the reality is as mentioned, that he had sexual intercourse with his wife after the break of Fajr in Ramadan, thinking that the night did not elapse, he is not sinful because he did not seek to have sexual intercourse in the daytime in Ramadan. However, he and his wife have to make up for that day and they are obligated to observe the expiation of sexual intercourse during the daytime in Ramadan. The expiation is to emancipate a Muslim slave. If he does not find one, he should fast two successive months. If he cannot fast because of old age or illness, he should feed sixty poor persons. The wife is the same in this regard if she did so willingly. If she was unwilling, she is required only to make up for that day. It is obligatory on him to repent sincerely to Allah from that act and not to be negligent in this regard. This is by making sure of the break of Fajr in order not to spoil your fast.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.