I cannot speak for others, but my impression is that many astronomers think nothing of working 60 or more hours per week. Those who are single or divorced ( there are lots of them in this rather harsh profession) can devote even more time. For myself, my direct 'day job' gets 40 hours of my time. My family gets the rest, and I will not waver from that situation except on rare occasions when I have to 'go observing' or attend a meeting each year or so. What has happened recently to change this a bit, is that I spend 2-3 hours in the mornings when they are asleep, working on this website and working on book writing. This is not time taken from the family, however.
Now, because astronomy is a cerebral area of work, even when you are shopping or playing with the children, your mind can and does wander to issues that have to do with astronomy. You can never really disconnect from your research when you come home, but at least you can mull over this work during pauses in the family activity. If you add up all of these passive forays into astronomy beyond 40 hours a week, you might easily get up to 60 hours, involved in planning what you will be doing when you get back to the lab tomorrow morning, or how you will prepare a lecture.