The sky quality in San Diego as measured by our SQM project members, which accumulates new data every new moon.

What is a sky quality meter?

A sky quality meter is a reader or measuring instrument that rates the darkness of the night sky.

What are the different scales?

The SQM scale:

The Bortle Scale is a 9-level reference to estimate the darkness of a particular location or observing site. It is helpful for amateur or visual astronomers and gives a simpler contrast between levels.