You can see from our (now out of date!) image that GZ2 volunteers marshalled by a team here at Oxford have already topped 300,000 classifications but they need more people to join in and take them surging passed that one million mark.
It's a fun idea but with serious intent, Oxford's Chris Lintott tells us:
'To keep track, we've added the world's first Zoonometer to the front page of the Galaxy Zoo site at www.galaxyzoo.org, so people can stop by and watch the classifications roll in.'
'Completing this challenge will not only be another significant step towards our goal of producing the world's largest and most detailed catalogue of classified galaxies, it's also a good chance to demonstrate just how effective all of our volunteers' efforts are when taken together.'
100 Hours of Astronomy runs until 5 April and is a key part of celebrations for the International Year of Astronomy.
Dr Chris Lintott, one of the founders of Galaxy Zoo, is based at Oxford's Department of Physics.