The cause of that explosion or shock was not observed visually.

The fact that a visually observed impact between two bodies in the physical world is normally associated with a particular sound has to be learned.

Due to its low surface brightness, it is a very difficult object when observed visually.

The pair was also observed visually by Coteau in 1973.

It can be observed visually, using a 30-35 cm or bigger telescope under a very dark sky.

It can be observed visually as a "red concrete cubicle".

The galaxies on the list can be observed visually and do not require special photographic or imaging equipment.

A navigating officer on one of the transports visually observed the American force minutes later.

"The only way we can give a person a ticket for littering is if we visually observe them in the act," he said.

The explosions were not visually observed due to thick clouds covering the volcano's summit.