How localised are seeing measurements

[pete_l]

Take a professional observatory that has the ability to measure seeing - and measures a value of (say, for example) 0.8 arc-sec. at some given time.

How far away from the point of measurement would you expect that value to hold true, or even just be indicative? Would it be just at the observatory itself, within 1km, 10km, 100km

[FraserClarke]

It depends hugely on what part of the atmosphere the seeing is coming from. If it is low level (<100m) then it will be very local and dependant on (mainly) the shape of the mountain and the wind direction. If it is high-level jet-stream associated, it's going to be similar across 100's of kms.

For most professional observatories though, you assume it is generally similar within a few 100km -- but that every mountain-top may be different due to local effects!

Are you thinking of any particular professional observatory?

[iwatkins]

Measured seeing? I would guess it to be totally local.

Even if you are within a couple of kms of the site you almost certainly won't be at the same altitude and hence in different air. Even if at the same altitude and within a few kms, you are still going to be on a different hilltop and hence again, different airflow, boundary layer mixing, humidity etc. will all be different.

As TeaDwarf suggests though it can be indicative if most of the instability is at high levels.

Cheers

Ian

[dph1nm]

Actually about 10 feet way I think! I have yet to meet a professional observatory where the seeing estimates agreed between telescopes on the same site (or even with seeing monitors within the same dome in some cases!).

NigelM