Seeing and Transparency Scales

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2020-01-10

This is handy! From http://www.astrologs.com...

Astronomical Seeing (Atmospheric Stability)

1. Severely disturbed: Low powers unsteady
2. Poor: Medium powers unsteady
3. Good: High powers unsteady
4. Excellent: High powers soft
5. Superb: All powers steady

Transparency (Clarity) Scale

1. Mostly cloudy
2. One or two Little Dipper stars visible
3. Three or Four Little Dipper stars visible
4. Five or Six Little Dipper stars visible
5. Six Little Dipper stars + Milky Way with averted vision
6. Milky Way + M31 + seven Little Dipper stars visible
7. M33 and/or M81 visible

This is a handy guide as often when I'm observing I want to make a note of the seeing and transparency but I always "gut" feel it as 1-5 for seeing and 1-7 for transparency. This gives me a bit more of an objective way to rate it.

Note: my main telescope is an 8" Meade SCT, so for me low power is with my 32mm Plössl (64x), medium power would be my 15mm Plössl (135x) and high power would be with my 8mm Plössl (254x). I have had nights where the seeing was a 5 and the transparency was a 7 - those nights are super-rare and to be treasured!

I'm just recording this for future reference. Hopefully it will help others as well!