Astronomical Seeing
In astronomy, ‘seeing’ has a meaning that is significantly different than its typical everyday use. Astronomer use the term ‘seeing’ to describe the steadiness of the atmosphere, typically as it relates to viewing Solar System objects such as the the moon and planets. The better the seeing, the steadier the planet will appear in the eyepiece or camera. Better seeing means sharper views with more contrast and more detail. Similarly, better seeing nets better results when imaging the planets (and moon, and sun, etc.) As you will see, the difference can be quite stark!
The images below represent the real world effects of seeing on a Solar System object. Of course, there are many other factors to take into consideration when discussing the images that a telescope produces – such as optical quality, collimation, aperture, focal length, angular size and more. These are very important considerations. I believe that seeing however, trumps them all.
The differences in the sets of Mars images below are due to the differences in seeing on the 11th / 14th, and 19th / 23rd. All four images were taken with the same telescope, ADC (atmospheric dispersion corrector), and camera. Very similar processing techniques were employed. The primary difference: seeing!
The image on the 23rd is a case study in how seeing can change – more than just night to night; it can change within minutes. I was in the observatory for about 3 hours imaging Mars on the night of November 22/23. A few hours into the session, seeing suddenly improved. Those moments of great seeing only lasted for about 10 minutes, and then it returned to being average. I was able to get three video captures during those 10 minutes.
