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weird Jupiter viewing

Angelika

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solarwallace

solarwallace

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Probably a combination of moisture in the atmosphere and heat rising from the earth. This can be a local problem or more global. Pointing your scope above other houses can cause this problem as they release heat, or as mentioned it can be a more general issue. It's a bit like looking through water isn't it?

Someone probably has a more scientific explanation. This is called 'seeing' by the way. So it's sounds like the seeing wasn't particularly good for you. It was certainly damp here where I had the same problem.

Steve

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solarwallace

solarwallace

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Posted

Hi

Sorry I perhaps wasn't being clear. I wasn't referring to dew although I did refer to 'damp' but not exclusively. That'll teach me to type replies too early in the morning when I'm not awake :p

The atmosphere isn't stable and conditions can vary. You're basically seeing the air 'wobble' in front of you. We're all effectively sat at the bottom of the atmosphere here on earth and it's not always steady. There are currents of heat and movement etc.

Perhaps a better explanation can be found here:

Astronomical seeing - Wikipedia, the free encyclopedia

Regards

Steve

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jgs001

jgs001

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It sounds like thermal currents to me. Either the scope needs time to cool to ambient temperature, or you're looking across the top of a heat source. Even a hedge or trees will emit enough heat to cause a shimmering effect, but houses are worse. And if you should happen to get a boiler flue beneath your sight line, that'll mess it up big time

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jimmyjamjoejoe

jimmyjamjoejoe

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As stated above, sounds like thermal currents to me, the same as when you look across hot asphalt in the blazing sun, you get that wavy "mirage" effect just above it. That exactly whats happening just on a larger scale. The heat differences in the air cause density changes and movement, and what you're seeing is tiny density changes over miles and miles of atmosphere.

You have to appreciate the distance of atmosphere you're looking through means what you're doing is as demanding as trying to look at the moon while sitting on the bottom of a swimming pool. Some nights it'l be still like a millpond, other nights things like wind will ripple the surface. That is what we refer to as the "seeing", when someone says the seeing was good, it means the atmosphere was nice and still.

As for the dew, it doesn't have to be particularly moist, and you probably wouldn't see dew literally dripping off of everything around you before it affects your scope. All it needs is a difference in temperature and a slight bit of moisture in the air. Try keeping your scope somewhere closer to ambient temperature, and consider investing in a dew shield, they're pretty cheap.

hope that helps

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studio1one

studio1one

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if this was last night there was so much moisture in the upper atmosphere it was unbelievable. The seeing was terrible where I was and from what I gather across much of the country. Those hot days suck all the moisture up into the upper atmosphere and it stays there until it gets cold and sinks again, we woke up to thisck mist here.

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John

John

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if this was last night there was so much moisture in the upper atmosphere it was unbelievable. The seeing was terrible where I was and from what I gather across much of the country. Those hot days suck all the moisture up into the upper atmosphere and it stays there until it gets cold and sinks again, we woke up to thisck mist here.

Yes, last nights seeing was pretty poor. It improved a bit as Jupiter got higher in the sky ( a little less atmosphere to look through) but even then was a bit below par. I put it down to the unseasonably warm weather at the moment :p

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michael.h.f.wilkinson

michael.h.f.wilkinson

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It's definitely a seeing problem. Even when Jupiter is fairly high, even 200x (which I routinely use) in my scope was pushing it. 120x even showed seeing problems. Bad seeing does not need moisture, just currents of air of different temperature (and therefore different refractive index). Think of the shimmering views of lions on the Serengeti. Those are taken with telephoto lenses of some 400 to 800 mm maybe. When viewing Jupiter, your scope act like the equivalent of a 15,000 mm telephoto lens (when compared to 35mm format). This means you are magnifying the problem by 20, compared to a 750mm telephoto. You therefore do not need Serengeti-style heat to have a serious observing problem.

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Angelika

Angelika

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Now it all makes perfect sense, thank you very much. As I was reading all the posts I had an AHA moment...I'm getting slow in my old age :-).

Thank you everyone, I really appreciate the help and advice.

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michael.h.f.wilkinson

michael.h.f.wilkinson

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roll on the frosty days. us lot must be the only ones who love the cold frosty days. maybe we should of been penguins lol

Actually, frosty nights with twinkling stars mean bad seeing. The twinkling is caused by turbulence. It is not the temperature that is linked to strong convection currents in the air, it's temperature differences.

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John

John

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Yes, last nights seeing was pretty poor. It improved a bit as Jupiter got higher in the sky ( a little less atmosphere to look through) but even then was a bit below par. I put it down to the unseasonably warm weather at the moment :p

Tonights seeing seems to be even worse :eek:

I can hardly make out more than the 2 main belts on Jupiter at the moment ;)

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great_bear

great_bear

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what you are seeing are normal conditions there are not too many nights where the seeing is described as good

Depends on the time of night. I find that around 1:30am on most nights my lunar/planetary views at around 300x are still as a mill pond. Only for about 20 mins, but still nonetheless.

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