Freddie was born September 5, 1946, in Zanzibar, Tanzania. I regard the birth time of 5:50 AM as Class B data because, though it came from a family member, we have the information second-hand, from a biography. (The date and place are documented on a birth certificate.)
As for the time, the main information comes from Waldemar Januszczak's article, "Star of India," in the Sunday Times Magazine November 17, 1996, page 61. He quoted his interview with Freddie's brother-in-law (his sister's husband):
Freddie took the self-renaming seriously. It seemed to have a spiritual import for him. Brian May is quoted as saying that when Freddie wrote, in the song "My Fairy King," the line, "O Mother Mercury, what have you done to me?," Freddie then told Brian, "Well, 'm going to become Mercury because the mother in this song is my mercury and so I'm going to become Mercury." (This is an example of what I call the spiritual dimension.)Freddie's English brother-in-law, Roger,... insists that [Freddie] chose the name because Mercury was his rising planet. 'When he told me, I said, it's a bloody good job it wasn't Uranus. Freddie never forgave me for that.' Kashmira, Freddie's sister, gives Roger a look. He says no more on the subject.
The brother-in-law story is quite believable and has the kind of detail and reaction that gives it life. I'm inclined to believe it tentatively. However, against it is one possible contradiction. A week after Freddie's mother died, another biographer confirmed that Freddie's mother had told her that she gave birth during "office hours" and Freddie's father was notified while he was at work. This doesn't sound like a chart for just before sunrise. So we have to test the chart to filter between these two.
The basic chart is sound in any case. He had a Leo Sun - the master ringmaster who owned the house, had an ego as big as the heavens, and yet saw the heroic greatness in everyone else as well. His Moon was in Sagittarius regardless of time, which fits the character well. Also, in dying of AIDS consequences, he technically tied of pneumonia, which is a perfect fit for Sagittarius Moon.
He also had a close Venus-Jupiter conjunction in Libra. With his luminary signs, this shows well his flamboyance and related traits. For any time of day, his Leo Sun was octile Venus-Jupiter. For the 5:50 time, Moon closely sextiles it.
But when you take this time and relocate the chart to London - where he grew up, where he broke out, and the enter of his fame - the Venus-Jupiter is exactly angular, Venus being mere minutes from IC. The other planet I would have expected to be strong for Freddie is Pluto - self-characterized as an extreme loner, intentionally living on the outskirts, trying to shake labels and limits - and it does show as moderately foreground for London, where he spent nearly all his life. (Pluto is 7° above Ascendant in 2° mundane conjunction with Saturn.)