On the 6 April 1699 a baptism is taking place at the church of All Hallows on the Wall on the northern perimeter of the City of London. The child – a boy – is named Edmond after his father, but his father – Captain Edmond Halley – is unaware of his son’s existence…
Edmond Halley married Mary Tooke on 20 April 1682 at St James’s Dukes Place, a short walk from his father’s house in Winchester Street. The marriage took place less than 3 months after Halley returned from his Grand Tour and it isn’t known whether he and Mary were acquainted before he left, or if the marriage was arranged while he was abroad, or after his return, or whether Edmond or Mary had any involvement in the decision.
What is known, is that the marriage was a great success. They were married for almost 54 years until Mary’s death in 1736, which Edmond described as “the saddest day of my life” and that he had lived “in great contentment” with Mary. 
At the time of Edmond’s departure, they had two daughters, Margaret, born 1685, and Catharine, born 1688. The Biographica Britannica says they had several children who did not survive, but I have only found a record for one, Katherine, born while they were living in Islington, where they’d set up home after their marriage. 
There are very few glimpses of Halley’s personal life but those few give the impression of a close and happy family. Flamsteed describes a visit in 1712 by the entire Halley family at a time when relations between Halley and Flamsteed were at their nadir, and one senses the cheery Halleys working together to make the visit less of an ordeal for Edmond (and Flamsteed).
Halley’s gravestone, now set into a wall at the Greenwich Observatory, was erected by his daughters (his son had already died) and dedicated to Edmond and Mary as the “best of parents” (optimis parentibus) and all four are buried together, along with Catharine’s second husband, Henry Price.
Yet despite their long and happy marriage, Mary hardly makes an appearance in the written records. The Biographica Britannica describes her as “a young lady equally amiable for the gracefulness of her person and the beauties of her mind” but we know nothing else about her character or personality. 
In spite of this, it’s Mary I most often think of when reading Halley’s logbook. I tend to think of her as being the type of person who was very supportive of Edmond’s various projects – that’s speculation but even if it’s correct, she must have been gravely apprehensive about his voyage.
Besides her concern for Edmond’s safety, she must have worried about what would happen to her and her two daughters if he didn’t return – and then shortly before Halley finally set sail, she found she was pregnant again – a hazardous event in itself.
We don’t know of any letters Edmond wrote to Mary from his ship, but he must surely have written at every opportunity to let her know he was safe and well. He was unable to write to the Admiralty between December and early April, and so presumably Mary had no word either and at the time of giving birth to their son, would not have known whether her husband was still alive. It must have been some sort of comfort to be able to name the child after Edmond.
And what of Halley’s own concerns for his family? We know he wrote a will shortly after the voyage was proposed and so was not blind to the fact he might not survive it, but I wonder how much consideration he gave to what would happen to his wife and young daughters if he didn’t return? I don’t doubt Halley would have been concerned for his family but I do wonder if his optimistic personality may have led him to underestimate the dangers of a long sea voyage.
Perhaps it’s more pleasing to reflect on the scene when Halley does return to his family: the relief of his wife, the joy of his daughters, his own delight at finding he has a son. For Mary, however, the relief will be short-lived as Halley will set off on his next voyage just two months after his return – and Mary Halley will have to spend another year wondering if she will ever see her husband again.
 The remarks by Halley about his wife are quoted in several books but I can’t locate the original source
 The spelling of Catharine’s name varies, ‘Catharine’ is used on the gravestone so I have opted for that. Biographica Britannica, Vol IV (1757) p 2517 note RR for the remark about his having several children. Catharine and Katherine were two different daughters as the latter was born before Margaret but Catharine is described as Halley’s younger daughter on the gravestone
 Biographica Britannica, Vol IV (1757) p 2500