NEW YORK, Aug 21 (Reuters) - U.S. stock futures trading volume fell during the two hours on Monday that people across a large portion of the United States donned special glasses to catch a glimpse of the first total solar eclipse to unfold across the country in nearly a century.
The moon blacked out the sun as the solar eclipse marched from the U.S. Pacific Northwest to the Atlantic Coast.
About 174,000 S&P 500 e-mini futures futures changed hands over the two-hour period ending at 3:30 p.m. E.T., down about 46 percent for the comparable period last year. Trading volume for the two-hour period was nearly a third less than the average trading volume for all comparable two-hour periods this year.
Overall, 5.26 billion shares changed hands on Monday, compared with average volume of 6.36 billion over the last 20 sessions, according to Thomson Reuters data.
Traders, however, said it was difficult to say with certainty that the eclipse was the reason behind the subdued volume. August is a relatively quiet time of the year as it coincides with summer holidays in the Northern hemisphere.
"It's a cool thing. Yes, I will stop and go outside and check it out in a couple of minutes," said Joe Tigay, chief trading officer at Equity Armor Investments in Chicago.
"The market does look thin, but it's been thin most of this summer anyway," said Tigay, who was working from home on Monday because he has a week-old baby.
While the total eclipse did march across a swath of the United States, in most places, including Chicago and New York, there was only a partial eclipse, though it still offered dramatic views.
With more than 95 percent of S&P 500 companies having already reported second-quarter results, there are fewer catalysts to spur trading.
Traders at the New York Stock Exchange took turns to step outside to get a look at the rare astronomical event, according to Ken Polcari, director of the NYSE floor division at ONeil Securities in New York.
"There may be fewer people sitting at their desks as everyone goes out and tries to get a glimpse of it," Polcari said.
Increased use of computers and algorithms for trading is another reason market watchers were hesitant to attribute the lower-than-usual volume to traders stepping away from their desks to view the eclipse.
"The truth is you don't even have to be there anymore," Polcari said. "Once you put an order in an automated system, as long as you get the proper limits on there, the order is going to continue to trade." (Reporting by Saqib Iqbal Ahmed and Chuck Mikolajczak; Additional reporting by Stephen Culp; Editing by Leslie Adler)