'seeing' conditions

[asimov (John)]

Here's something that Iv'e often thought about but not discussed/mentioned with anyone..

Let me give you 2 examples:
1 One night I was outside viewing, it was a good night for viewing, not a breath of wind. But the stars were twinkling a LOT which supposedly means, or defined as bad 'seeing' conditions, yes? Sure enough, terrible views threw the scope.

2 On another occasion, outside viewing, identical conditions to the 1st night. EXCEPT there was a gentle breeze blowing. Again, stars twinkling a LOT. The scope was moving about a bit but the views threw the scope....Very good!

So now, In order to be able to tell how the 'seeing' is, (from my 1st hand experiences) with the stars twinkling a lot, as long as there is a gentle breeze blowing, it's going to be BETTER 'seeing' than with no breeze. (I'm not saying perfect here!)

Naturally with no breeze & no star twinkle: This is the best conditions, but as we all know, that's a rare occurrence.

Is this common knowledge to most astronomers? ( It could be I'm "out of touch" with some things astronomically) Or is this 'phenomenon' perhaps confined to this particular area where I live?

Your thought appreciated.

Thanks.

[Argonavis (William)]

John
I understand that most seeing is caused by conditions in the upper atmosphere. I would not have thought that a gentle ground breeze should affect this greatly. Was the eyepeice and magnification you were using in scenario 1 and same as scenario 2? Don't forget seeing can change from minute to minute. This hobby demands patience and perseverence to wait for the good bits.

[slice of heaven]

Hmmm interesting.
Now I always thought the 'ground atmosphere' had as much to do with seeing as the high atmosphere. Otherwise why would they place observatories on high points?
Local conditions play a big part too...hill and mountain ranges..heat haze..sea breezes..wind directions. I'm only 60 Kms from Rumples Riot but theres a big difference in seeing conditions.He's posted shots at times thats had me scratching my head how he got them and other times its been perfect here but not for him.
Dont know the answer to this one,for me I know my location and the best conditions.Summer time here produces the best seeing more often than winter.

[elusiver]

yeah i thought it had to do with the 'ground atmosphere' as well.. cause i read somewhere thats why seeing was worst lower to the horizon.. as to the gentle breeze.. makes sense.. if you thing of things that cause bad seeing as a 'fog' type thing... it's harder for fog to 'form' and settle when there's a breeze.

it's also why they have smog alerts in the cities if there is going to be no wind and all the pollution and stuff just sits and collects.

el

[ausastronomer (John Bambury)]

From my experience the upper atmosphere and lower atmosphere can have an effect on seeing conditions.

CS-John B

[asimov (John)]

Argonavis....Same EP yes.


I haven't come to any great scientific conclusions on this subject LOL...I just know it makes a difference between the 2 different 'scenerio's' described. Hence Iv'e changed my way of thinking as to being able to distinguish between good 'seeing' & 'mediocre- seeing'. I think LOCATION might play a part in it yes slice.

EL, yeah it does make a kind of sense.....clear as MUD hey! LOL

Thanks for your thoughts & comments guys!

[slice of heaven]

Dont dust, smog and moisture have more to do with transparency than seeing? Having a breeze remove them helps the viewing though.
In the summer time here we get stiff sea breezes that absolutely strips the atmosphere of dust and cools the land of to remove the heat haze. The view around midnight is brilliant.
I've found viewing the sunset gives a good indication of the expected seeing, the bluer the sky near the horizon,the better the seeing.

[MiG]

From the graphs of turbulence vs altitude I saw in an adaptive optics paper, both high and low altitude air affects seeing.

[Argonavis (William)]

Quoting Sidgwick, most of the turbulence is a couple of kms up - which is why the seeing conditions can be the same (either poor or good) across a wide area. Of course there are topographical influences with local air masses moving around hills and valleys and packets of hot air rising from flat plains (like central Victoria). Experience is the best judge of where and when the best seeing is. I would have thought twinkling of stars would be directly correlated with the seeing conditons, but tube currents and dew can also be a factor with the view through a telescope. Having a light breeze is brilliant for keeping away the mozzies and dew, and possibly cooling down the telescope tube to allow thermal equilisation. These factors would certainly give the perception of better seeing.

[Argonavis (William)]

Actually tube currents can be a real problem - my first telescope have a metal tube and I could see the waves of hot air drifting off. Then the metal tube cools to below the dew point and collects lots of dew. Pain. Metal does need to be insulated.