| Seeing | |||||||||||
| 1 = | Bad | Severely disturbed skies: Even low power views are uselessly shaky. | |||||||||
| 2 = | Poor | Low power images are pretty steady, but medium powers are not. | |||||||||
| 3 = | Average |
Can use about half the useful magnification of your scope. High
powers produce fidgety planets. |
|||||||||
| 4 = | Good | Medium-powers are crisp and stable. High-powers are good, but a little soft. | |||||||||
| 5 = | Excellent | Any power eyepiece produces a good crisp image. | |||||||||
| in arc-second | |||||||||||
| I | > 4 | Boiling image without any sign of diffraction pattern | |||||||||
| II | ~ 3.0-4." | Important eddy streams in the central disc. Missing or partly missing diffraction rings | |||||||||
| III | ~ 1.0-2.0" | Central disc deformations. Broken diffraction rings | |||||||||
| IV | ~ 0.4-0.9 | Light undulations across diffraction rings | |||||||||
| V | < 0.4" | Perfect motionless diffraction pattern | |||||||||
| Transparency | |||||||||||
| 1 = | Poor | Mostly Cloudy - Partly cloudy or heavy haze. 1 or 2 Little Dipper stars visible. | |||||||||
| 2 = | Below Average | Cirrus or moderate to slight haze. 3 or 5 Little Dipper stars visible. | |||||||||
| 3 = | Average | No clouds. Milky Way visible with averted vision. 6 Little Dipper stars visible. | |||||||||
| 4 = | Above average | Very Clear - Milky Way and M31 visible. 7 Little Dipper stars visible. | |||||||||
| 5 = | Transparent | Extremely Clear - M33 and/or M81 visible. | |||||||||
