Worst seeing in history

[PSALM19.1]

Ok, so Saturday night was THE worst seeing I have ever seen...or not seen...or whatever....Saturn looked like one of those glow in the dark planets that kids (and a few adults) stick on their ceilings...no Casini, no stripe, no nuthin'! Even the moon was bad...could it be the strong winds maybe....? :shrug:

[Astro_Bot]

I'm no expert, and there are other factors, but the jetstream was pushing 140 knots in places over the weekend in NSW and southern QLD.

(I idly wonder to myself whether wind speed and direction at other altitudes play a role - creating wind shear or other turbulence - I think they probably do).

[kkara4]

today the jetstream is again extremely fast, but wind direction at all heights is largely the same today, so I wonder how this will correspond to seeing, since this means there is little vertical shear.:shrug:

[Rob_K]

All relative I suppose. Here the worst seeing is when Saturn is being ripped apart, bad seeing is when it's a shimmering blob & you can vaguely make the ring out, fair seeing is when you can see the ring & disk clearly, good seeing is when you get glimpses of the Cassini Division in moments of steadiness, and excellent seeing is... well, I've no idea actually! :P

That's what you get when you live at the bottom of a deep east-west valley on the western side of the Great Dividing Range. Thermal-city with easterly wind drift, cold air cascading & funneling down from the Alps, and differential heating of the valley sides. That's before you even get to jetstream etc!

Cheers -

[PSALM19.1]

oooh wow...then I actually had pretty good seeing..Saturn in one piece...should stop complaining....:lol:

[Rob_K]

LOL! :thumbsup: :lol:

[Rob_K]

Hehe, I remember one Snake Valley camp that I took a webcam to: I put Saturn in the field of view and WOW it was like I'd never seen it before! Then I overheard a grumpy group of planetary imagers complaining about the rubbish seeing... :rolleyes:

[Suzy]

Shaun, you say you were observing in strong winds?
Wouldn't it make your telescope go *boing* *boing* *boing* and everything in the image go all blurry:question:. My dob does and that's when I wave the white flag and give up :sadeyes:. Or have I mis-understood something maybe? :ashamed:

Poor Rob :lol:. And big giggles Shaun at your reply to him :rofl:.

[julianh72]

At my place, I'm pretty well surrounded by fairly tall trees, which limits my view below about 20 degrees elevation, but does provide protection against strong wind at ground level.

Last night was very blowy, but calm at ground level - no detectable telescope movement. The air has been clear the last few nights, but seeing has been terrible - I have assumed that the high prevailing wind speeds have been the main problem.

[Doogs38]

Yep, last night was terrible (as shown on skippy too) ... there seems to be quite a jet stream associated with the high pressure system situated over QLD :-// If I'm interpreting the BNE aerological diagram correctly, the jetstream at 30k-35k ft is 150+ knots! No wonder Saturn looked liked a mushy white ball. :sadeyes:

[Suzy]

Thank you for that Julian :) .
Quite an education from Doug too. :thumbsup: So Jetstream hey... I don't fully understand Jetstreams. This probably explains why the seeing was so terrible here in Brisbane on Saturday the 6th too then :sadeyes:. It was beautiful and calm that night but got incredibly windy later in the night after I'd finished observing. I was observing asteroids Ceres and Vesta and Saturn's moon Iapetus which only makes an appearance every 70 odd days. Saturn was tragic & the stars just wouldn't hold focus. But the asteroids close encounter totally rocked!:D

[PSALM19.1]

Thankfully where I observe from is pretty sheltered from quite strong winds...was hopeless when I had a smaller refractor but the Dob seems to be stable enough...last night seeing was quite good and it was still quite windy...and cold!:)

[alistairsam]

hi Alex,
would you have a link to this data?
I mainly image DSO's and they are a bit less affected than planetary but it can still throw out some high fwhm's so checking jetstream conditions might help.

Cheers
Alistair

[kkara4]

http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-218.50,-23.50,3000

click on the earth button to change settings, that link is for 250hpa. click anywhere to get a reading on your selected data which is displayed when you click the earth button

[Astro_Bot]

Actually, I think he meant these ones:
Aerological Diagrams (http://www.bom.gov.au/aviation/observations/aerological-diagrams/)

There are several jetstream charts. I find the BoM chart equal or better than others:
Jetstream Chart (http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=windbarb&level=200hPa&tz=AEDT&area=Au&model=CG&chartSubmit=Refresh+View)

Whilst the earth.nullschool.net diagram is very impressive looking, I find it doesn't tell me what I want to know.

[Doogs38]

Thanks astro_bot - that's exactly where I get my jetstream info from. It takes a little practice to understand what they're saying, but it's not rocket science :-) Today's chart shows there are still 100-140kt winds from 30k ft and up :-/// I'm not an expert, but IMO 140kt = badness :sadeyes: That said, it doesn't stop me getting my scope out, it just helps greatly with expectation management of what I'm going to see :D You can actually 'see' the jetsteam in your eyepiece if you defocus slightly; it looks like a bunch of rapidly flowing, closely spaced parallel lines.

[ianB]

Yes thats what i have seen when the JS is high.
Re your comment Suzy, i will try and have a look at those asteroids as well, at first i thought it would not be possible to see them with a high JS but you obviously had a good view so thats encouraging.

[kkara4]

It tells you all the windspeed if you click any point on the map and then hit the earth button and it tells you the windspeed. Other than that im not sure what else you need to know!

Those aerological diagrams are good though, ive been looking for those charts for a while, thanks!

EDIT: actually clicking anywhere brings it up automatically in the bottom left corner, wind speed and direction and the GPS coordinate of the spot you clicked.

[Astro_Bot]

I've been watching it for months - it looks really cool and is nice for a hemispheric overview, but that's not helpful (to me) for judging/planning astro sessions. It requires way too much work (too much clicking) to get useful information, whereas with the BoM chart, I can get all I need in a single glance, and quickly sequence through the forecast at 3 or 6-hour intervals. But each to their own. :)

[kkara4]

Ah fair enough, sorry just wasnt sure what you found difficult about it is all! I do like the forecast ability that you speak of though, maybe early next week we might get some half decent seeing!

Im getting the scope out no matter what tonight, got some new toys I need to test out haha