What was Tom Hanks doing with his thumb in the movie Apollo 13 while looking at the Moon?

I gather there was a scene where he was holding his thumb out at arm's length towards the Moon. I suppose he was doing any one of the following:

1....Admiring a hangnail by Moon light

2.... Noticing that the thumbnail at arms length covers the disk of the Full Moon

3.... Creating a total digital eclipse of the Moon

4.... Noting that this is the last time that the Moon will subtend to his vision, something as familiar as a thumb; the standard of lunar measure bu humans for the last 3 million years. In a few days, it will appear much larger as the Apollo 13 capsule brings him closer to the Moon.

I suppose there are other possibilities too!