[Astro_Bot]

Originally Posted by Shamrocker

Probably a silly question but can anyone tell me how to read the seeing index on skippy sky! In Brisbane tonight it seems to me to be quite hazy and the seeing is poor.

Seeing was bloody awful tonight (at least where I was, looking west over the city!).

The SkippySky seeing map reads like isobars on a weather chart - use the colours and lines to determine what the boundary values are, e.g. the boundary between yellow and green is '4' and the yellow zone would be seeing between 3 and 4.

The scale of seeing used is 1-10, and is probably the modern Standard Scale, which is (from here):

The version given by the editors of Sky & Telescope as A Scale of Seeing (with clarifications adopted from Sidgwick, p.467) is representative of these modern versions of the Standard Scale:

1 — Airy disk and diffraction rings are blurred together; star image is about twice the diameter of the third diffraction ring (if the ring could be seen); star image 13 arcseconds (13") in diameter.
2 — Airy disk and diffraction rings are blurred together; image occasionally twice the diameter of the third diffraction ring (13").
3 — Airy disk and diffraction rings are blurred together; image about the same diameter as the third ring (6.7"); the central Airy diffraction disk is not visible, but the image is brighter at the center.
4 — The central Airy disk is often visible; short arcs of diffraction rings briefly seen on brighter stars.
5 — Airy disk always visible but is mobile; short arcs of the diffraction rings visible about half the time.
6 — Airy disk always visible though not sharply defined; short arcs of the diffraction rings continuously visible.
7 — Airy disk sometimes sharply defined, and distinct from rings; diffraction rings seen as long arcs or complete circles.
8 — Airy disk always sharply defined; innermost ring seen continuously but always in motion.
9 — Airy disk and innermost diffraction ring are stationary; the outer rings are momentarily stationary.
10 — The complete diffraction pattern is stationary.

If I was 'in the know' how would I gather this from Skippy Sky?

It seems to be a rough guide, but, like the weather forecast, not perfect. You can try running through the seeing map at different times to get an idea of how seeing conditions might change over time.

You can do the same with transparency.

Another resource given above, 7Timer!, uses (AFAICS) the Full Width at Half Maximum (FWHM) measure of seeing, which is described here.