We have had a lot of talking about finding a suitable method of rating “seeing” for our observing projects. While the most scientific way to rate “seeing” is to give a measure in seconds of arc, this method is time-consuming and involves some complexities. Moreover, this method is not 100% exact (what branch of sciences is 100% exact?) and can frighten newcomers to this field of Astronomy observing.
The following ratings are a mixture of the well known Pickering scale and a new fuzzy classification that allow us to determine a value between 0 and 10 based on the observer’s experience. While not deterministic or exact, its use is very intuitive, gives a unified framework to work with, and is very easy to identify on real situations.
Also, some humor has been added. Please, don’t understand it as a lack
of scientific rigor. Even such details will contribute to help you to better
determine the quality of seeing. Read on and enjoy.
| Rating | Description | |||
| 0
1 2
3
7
8
9
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Every double star you try is not splitable.
Better relax in your living room while reading a book, visit your friends
or initiate more productive tasks.
Only the most open doubles are splitable with difficulty. Almost
no diffraction rings. The sensation is like "looking up from the bottom
of a swimming pool". Probably, your new refractor is having its first
lights after two weeks of clouds. Same recommendations as for classification
0 apply here.
Seeing very similar like observing from inside your living-room
in winter without waiting for thermal equilibrium. 3 stars in the Trapezium
are resolved at 40x during few seconds. Delta Orionis is observed as a
double without problems.
It's difficult to use more than 50x, but every really open double
is splitable. This is the minimum level you can expect to start double
star observing. Maybe a bit boring for some people, but at least you can
observe some traces of coloration on the components. If after some time
of doubles observation you resign and start to hunt for faint-fuzzies,
then this is the more suitable classification that night.
Observing coloration in double-star components is easy, but Epsilon
Lyrae is not splitable yet.
Trapezium easy at 40x consistently, but using more than 100x
is a nightmare. Epsilon Lyrae starts to split during very short periods
of time.
Epsilon Lyrae is splitable almost 100% of time. Anyway, you can
use 28x per inch of aperture with your telescope. This is the minimum recommended
level to start making serious double star observing. You can measure separations
and position angles using a reticled eyepiece and remain observing doubles
along all the observing session.
Epsilon Lyrae easily splittable. You don't feel tired of observe
the beautiful diffraction rings on Castor while the time goes by. You feel
your observing session is really productive and your Barlow lens brings
out from your pocket.
Using a solar glass filter you can perfectly observe granularity
on the Sun's surface with a good 4" aperture achromatic refractor. Easy
to go up to 50x per inch of aperture using a refractor. Epsilon Lyrae splits
using 60x with this observing instrument and Antares splits at 250x when
located only 18 degrees over the horizon. You don't hear your wife/husband
when she/he calls you because she/he doesn't find the TV remote control.
This is the same as 10, but the seeing is not stable at all and
comes and goes, sometimes downing to 8.
Perfect Airy disk with textbook diffraction rings. Rules of maximum
theoretical magnification break. Good achromatic refractors able to take
up to 75x per inch of aperture. Apo and fluorite refractors reach 100x
per inch of aperture or even a bit more. This condition is stable.
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