From "A Modern Scale of Astronomical Seeing for Imagers" by Damian Peach. Damian Peach photo
Recently, famed planetary imager and long-time
Astronomy contributor Damian Peach e-mailed me and several other friends the following note that offers some practical help to observers:
Hi all,
After discussions among Mars observers lately, I decided to create a more “modern” scale of seeing with real video examples, not based on double star observations or for visual observers but directed at imagers using CCD cameras based on the live “on screen” planetary image.
I chose Jupiter as the subject as this is probably the most popular target among planetary imagers. I constructed a five-point scale that can be viewed at http://www.damianpeach.com/seeingscale.htm.
I hope observers will find this guide useful in helping them to judge the seeing under which they obtain images.
Best Wishes
,
Damian
I studied Damian’s videos at length, and they’re terrific. This represents a down-to-earth way of estimating seeing. Two days later, Damian followed up with this:
Hi all,
I’ve had a lot of feedback from people over the last few days — many thanks. I’m going to add alongside the videos the processed results of those captures to show what kind of results come from such video samples. Some points that should be considered are the following:
A scale of seeing is not something that is adjusted due to where you live. For example, “For my site, that is good,” etc. The fair rating may well be “good” for certain locations, but that does not make it good seeing conditions. If one were to measures the FWHM [Full Wave Half Maximum; the width of a wavelength’s peak at one-half its height, a measurement used to standardize observations] values as is done at observatories, this would become very clear.
Many have perhaps never experienced “the top of the mountain” as far as seeing goes, but the excellent video on my scale is a good example of the best seeing I’ve seen, likewise with the worst one being similarly so.
Also comparing the videos with captures through smaller telescopes will take some judgment because obviously such instruments will not resolve as much detail. Good estimation of seeing takes a lot of practice and experience at the telescope.
I don’t think it is possible to create a suitable scale showing every permutation of Earth’s atmosphere from fuzzy, jittery to rippling intermixed with fuzz and sharpness. You’d end up with so many different videos, anything easily usable would be impossible.
I’ve intended the scale as a guide based on my own experience. Others’ work may well produce a different looking scale based on their experiences. Perhaps it illustrates that the very finest seeing conditions simply do not occur from many amateur locations. Certainly some food for thought.
Thanks for the great effort, Damian!