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Transparency

How dim can you see?

Notes:

In the previous sections we have dealt with understanding how weather works and learning about some tools that will predict the coming weather. Those tools address the most obvious weather impact on astronomy

CLOUD OUT

But even a clear sky has perils for the astronomer. The first peril is transparency.

Transparency is a simple concept namely how dim an object can you see? Your telescope comes with specs that say it can see say a magnitude 15 object, but will the sky support that?

In this section we will ignore light pollution. That is both beyond our control and easy to control. The light impact on any site is known and relatively unchanging from day to day. Balancing convenience and sky darkness is something every astronomer has to do.

But even an excellent site in clear weather is not excellent all the time. The next two sections describe what can go wrong.