What's goin' on!!!!

matt · #1 13-05-2006, 11:22 AM

OK. A quick whinge. Then it'll be out of my system.

I set up last night, very excited, ready to get some Jupiter imaging done.

Excited, because the jetstream map showed plenty of gaping grey "hole" over my part of the world after weeks of blues and yellows.

Even the little arrows inside the grey showed a small degree of upper air movement.

Looked through the ep and blahhhhhhhhhh!!! It was horrible.

The stars were also twinkling like mad all night.

Ran a few avi's, but they're an absolute debacle!

Forget the maps. Learn to judge by eye

iceman (Mike) · #2 13-05-2006, 11:24 AM

Yeh I've found that lack of jetstream doesn't guarantee good seeing, but when there is a jetstream it almost always guarantees bad seeing.

Could've been elevation? mirror temperature? Just bad luck?

How long did you stay out for?

Don't forget that it's likely that the seeing improved to 9/10 as soon as you packed up

ving (David) · #3 13-05-2006, 11:26 AM

never been able to understand the whole jetstream thing... I have had a raging JS over head according to the various charts and had good seeing... go figure.
there was supposed to be no JS last night and every star twinkled...

matt · #4 13-05-2006, 11:33 AM

Quote:

Originally Posted by iceman

Don't forget that it's likely that the seeing improved to 9/10 as soon as you packed up

That's very funny and very true Mike

Stayed out there maybe 3 hours. Didn't look like the seeing was getting any better and went back inside to drink a few beers and be a grumpy old man!

But strangely, by the third beer, was a happy chappy again

Ahhhhhh beer. How we luv ya!

I think you're also right about the maps being helpful as a guide to bad seeing.

Had the scope out from sundown cooling. Jupiter was nice and high.

Was definitely just plain out of luck. Will be out there again tonight, though. The JS map looks great

janoskiss (Steve H) · #5 13-05-2006, 11:38 AM

You think you're upset! I drove 600km (one way!) last weekend out of desperation for some clear skies. It was looking very promising while I was on the road, and the forecast was clear skies for my destination. But by the time I got there and set up to observe, the clouds appeared literally out of thin air, and there was not a patch of clear sky left for the rest of the weekend!

So what do I do to ease the cloudy nights blues? Buy more observing gear!

Just to I have something else I cannot use.

matt · #6 13-05-2006, 11:42 AM

Quote:

Originally Posted by janoskiss

So what do I do to ease the cloudy nights blues? Buy more observing gear!

Just to I have something else I cannot use.

And people think we astronomers are a strange and unusual breed!

JohnG (John) · #7 13-05-2006, 11:51 AM

Yer got it wrong Matt, it's all the hot air rising out of Canberra. LOL

JohnG

matt · #8 13-05-2006, 11:54 AM

How true, John. How very true.

After all, it was Fed Budget week

Hitchhiker · #9 13-05-2006, 12:14 PM

Hi Matt, I had a look out side last night, early evening, and the stars were twinkling more violently all the way to the zenith than I have seen for a long time.

On the subject of the Jet Stream, I think the resources that we use show the Jet Stream strength at around 32,000 feet (300 millibar). According to this FAQ http://squall.sfsu.edu/crws/map_info...ream_info.html "This is very roughly the level where winds in the atmosphere are typically strongest".

If you have a look at the Aviation section of the Australian BOM you will find resources that show wind speed at different levels in the atmosphere (these resources are a lot more difficult to interpret than the graphs we usually look at with pretty colours indicating wind speed - all they have are numbers).

I think it is likely that, even though the 300 mb Jet Stream was quite good, winds at other levels in the atmosphere were very strong. I have to agree with iceman's statement that a "bad" jet stream as displayed by the usual internet resources will guarantee bad seeing, whereas a "good" jet stream does not necessarily guarantee the reverse.

matt · #10 13-05-2006, 12:18 PM

Thanks Adam

Yeah. Was quite something to see stars at zenith twinkling as badly as stars at horizon.

asimov (John) · #11 13-05-2006, 12:57 PM

Yeah, I saw the same map. And same scenerio, setup in hopes of some nice viewing. Ha! What a joke.

Astroman (Andrew Wall) · #12 13-05-2006, 01:32 PM

You also have to take into acount other atmospheric distubances such as inversion layers, smoke and the like. Smoke is not always detectable by the eye it can hide in the atmosphere. Also with inversions trapping heat would be worse than looking through a hot tubed telescope. It's not always easy to detect this sort of thing so judging by the eye is probably the best you can do.

matt · #13 13-05-2006, 01:37 PM

Andrew

I'm not familiar with inversion layers but I often see them mentioned.

Got any info?

Cheers

Gargoyle_Steve (Steve) · #14 14-05-2006, 12:55 AM

An inversion layer occurrs when you have 2 air masses, in this case meeting as layers of air one on top of the other. The 2 layers are usually at different temperatures so one mass of air is denser than the other, and often they may be moving in different, even directly opposite, directions as when a warm fron meets a cool front head on. The different densities cause not only distortion / diffraction to occur at the layer, but there is often not a "clean" separation but turbulence as well (like Jupiters separate atmospheric zones rotating against each other - same thing).

It's like looking through a reflector thats got a warm mirror on a cool night, except imagine tube currents not on a scale of 8 or 10 inches wide and a metre or so in height but dozens or hundreds of miles wide, and quite deep.

Astroman (Andrew Wall) · #15 14-05-2006, 07:28 AM

Pretty much what GS said.