bewildered by "seeing" estimates

[muletopia (Chris)]

Folks,
I read in many reports here that the seeing conditions were good or bad.The intent is clear, but many report "estimates" of the seeing on a scale from 0 to 10. I went on the web and found a good explanation of various seeing scales at

http://www.handprint.com/ASTRO/seeing2.html

This site gives a clear definition of the diffraction based scale which seems to be fairly objective.
But on this forum what do I make of "estimated seeing" and on which scale is it based
I can see a mag 3.5 (epsilon Crux) star tonight with my naked eye but I certainly have not counted the twinkles in a ten second period and could not give an estimate of seeing on any scale.

Which scale is used on this forum and how closely to contributions adhere to it?

Guidance please!

[ianB (Ian)]

Boy that site confused me, besides how is one to know if the star twinkled 26 or 33 times every 10 seconds, that page seems over complicated to me, i think it would be easier just to get the telescope out and have a look.

[brian nordstrom (As avatar)]

Yep .

Brian.

Originally Posted by ianB

Boy that site confused me, besides how is one to know if the star twinkled 26 or 33 times every 10 seconds, that page seems over complicated to me, i think it would be easier just to get the telescope out and have a look.

[barx1963 (Malcolm)]

I usually make a simple statement of either, poor, fair, good or excellent. Base on looking at a moderately bright star, slightly defocusing and seeing how much it jumps around. Transparency I do the same way by seeing how much I can see with naked eye.

I try not to get too technical.

Malcolm

[Varangian (John)]

Originally Posted by ianB

Boy that site confused me, besides how is one to know if the star twinkled 26 or 33 times every 10 seconds, that page seems over complicated to me, i think it would be easier just to get the telescope out and have a look.

x2 for me (if it's not too much of a hassle). I just wheel mine out of the shed.

[ianB (Ian)]

I was thinking of having a look at Mars tonight, i had a look at the stars just now and they are twinkling too much both near the horizon and high up, as such i will stay inside and watch a b grade movie. "Moon" ( 2009 )

( when i take the scope out and then find conditions are not good i usually bring the scope in and uncover the lens and rear cap and allow the inside to warm up, i also lightly rub down the scope and stand etc, all in all i leave it for a good 2 hours before packing everything all up again in a box, so rather than having to go through all that i now just judge seeing conditions by looking at how much or little the stars twinkle )

[The_Cat (Jeremy)]

If you would like to read about seeing measurement please see:

http://www.eso.org/gen-fac/pubs/astc...n/zanjan02.ppt

A particularly simple and portable setup is described here:

http://www.mro.nmt.edu/documents/int...ter/seneta.pdf

Jerry.

[muletopia (Chris)]

Thank you Jerry,
That explains a rational time/space resolution measurement of seeing. To set up DIMWITT for one's self would be a large undertaking, but possible. It would have to be taken on as a separate interest to looking and imaging. The comments on real time systems and gcc are interesting. Some microchip manufacturers provide real time c++, very cut down but with interrupt priority vectors. None as nice as the old Data General RDOS operating system. In general the GCC compiler is superior to Visual C++.

Any way it is clear that estimates of seeing here are based on the experience of the observer, related to a particular telescope?
So I will read reports with that in mind as no ordinary member uses adaptive optics!
cheers
Chris

[Wavytone]

Seeing is a function of atmospheric turbulence. Your microclimate around 1000 metres up is significant; largely a function of the local terrain around you. Then there's what's going on in the upper atmosphere, in particular the jetstream - strong winds = poor seeing.

You can find out what the upper atmosphere is doing, see http://www.iceinspace.com.au/forum/s...d.php?t=120291

[muletopia (Chris)]

Thanks Wavytone, practical advice, I have bookmarked that BOM page.
I will have to use Perth (200km north) not much out in the Indian Ocean.