It's a good thing financial media outlets aren't too shy about covering topics outside the financial sphere because without the eclipse, there would have been nothing to talk about today. Volume and volatility dropped off a cliff, abruptly. In fact, the difference in tone was big enough that I wouldn't mind chalking up some of the ABSENCE of trading as a symptom of the eclipse. In other words, it wasn't necessarily a market mover as much as a market inhibitor.
All that having been said, it would be hard to sort out just how much of the market's quietude was attributable to eclipse as opposed to the simple nature of the Summertime trading environment. Mondays tend to struggle for relevance in August regardless of astronomical events.
If the eclipse possibly didn't matter, why am I still talking about it? Again, because there's literally nothing else to talk about today. Bonds started in slightly stronger territory, but remained well-within Friday's range. Both MBS and Treasuries generally orbited Thursday's latest levels and we continue waiting on more liquidity and volume before getting a better sense of how this week will shape up.