Astronomers use the word
"seeing" to describe the steadiness of the atmosphere.
When you see the stars
twinkle, the atmosphere is unsteady. The view through your
telescope won't be as clear as it could be.
When the stars are still,
without a quiver, the atmosphere is steady and you will get the best
views through your telescope.
Transparency tells you
how clear the night is by finding the faintest naked eye star
visible. Naked eye means looking at the sky without a
telescope or binoculars, just your eyes.
Antoniadi scale of seeing. Use to describe the steadiness of
I - Perfect seeing without a quiver.
II - Slight undulations, with moments of calm
lasting several seconds.
III - Moderate seeing with large tremours.
IV - Poor seeing, with constant troublesome
V - Very bad seeing.
When you have an
astronomical log of your observations, you have to keep track of the
seeing each night.
You log in the
transparency of the sky by the magnitude of the faintest naked eye
You log in the steadiness
by using the Antoniadi scale of seeing.
Keeping accurate records
is very important if you find something new or if you want to keep a
record of how an object changes over time. Objects look
different when the seeing conditions change.
Astronomers often compare
notes of what they saw and the seeing at the time.