In the teaser scene, O'Neill does not seem interested in astronomy at all and seems to know nothing about it. However, he is an amateur astronomer, as indicated in numerous previous episodes.
O'Neill looks through the telescope that Carter has setup to try and see the nebula they are observing, during daytime, and acts surprised that he is not able to see anything. In previous episodes it has been established that O'Neill is an experienced amateur astronomer. According to supervising producer Joseph Mallozzi that was deliberate, allowing Richard Dean Anderson to "have a little more fun with the character".
As Major Carter is typing something into the keyboard connected to the telescope, the screen is off and there are no lights on of any kind indicating the laptop is even turned on.
At approx 02:04, the shadow of a boom mike is clearly visible on the sand next to O'Neill's shadow.