Ask HN: Sending a newsletter on a Friday?

I have a few thousands email subscribers for one of my project. I usually send them emails at the beginning of the week, and have good open rates (>50%).

However, this week I'd really like to send one email on Friday (tomorrow), and I'm afraid to get a lower open rate than usual.

Do you know if sending an email on Friday is bad for open rates? Any study about that, or personal experience?

Thanks!