In addition, observations of the sun required the navigator to look directly at the sun.

The observations required a clever technique which stretched the capabilities of modern instruments.

This observation required a new interpretation to make it compatible with Copernican theory.

The observations needed to accomplish these goals require a telescope that can study the Universe in infrared light.

What happens when observations don't fit with the accepted model and require a doctor to go back to first principles?

Most observations will not require the scientist who proposed them to be here in Baltimore.

Other observations may require correlation of catch reports with the vessel's presence in given areas.

The observation required finding a place where on a specific date the sun set into a notch on the horizon.

The researchers note that these observations raise more questions and require more follow-up.

Ground-based observations of the rings require the largest available telescopes.