Twinkle twinkle little star

[louie_the_fly]

Just ducked outside during a recent ad break for a sneaky look at the sky and I noticed that the stars (and Jupiter) appear to be twinkling more than normal. What's the reason for this? Could it be a temperature thing?

[Hans Tucker]

It means that the upper atmosphere is unstable/ turbulent and offering very poor seeing/viewing...yes it could be attributed to temperature....Jet Stream might be another factor.

[pgc hunter]

Seeing has been a disaster all summer here. Stars twinkling so severely that Arcturus and Aldebaran almost winked out of sight at times when low on the horizon when I was out on Sunday night. That night had an inversion though (warmer unsettled air sitting above a layer of cooler air) and in my experience inversions are a guarantee of awful seeing.

[louie_the_fly]

Thanks for that. Although it's really dark tonight, after a 2nd & 3rd look, the stars don't appear as bright as usual. In fact, M42 is barely visible.

[Hans Tucker]

Your area might also have a thin layer of high level cloud that seems to be the norm during hot summer nights.

[pgc hunter]

You are mistaking seeing for transparency. "Seeing" is the term used to describe atmospheric turbulence. For example, poor seeing at the eyepiece appears as blurry planetary images and bloated stars and higher magnification amplifies this effect. This occurs when the jetstream is present, or can be because of local factors, i.e. wind passing over buildings, trees etc causing eddies and other disturbances, and also simply because the atmosphere is made of several layers of air moving at different speeds and directions. When the atmosphere is stable through all its layers, and yo uare getting sharp planetary views and tight crisp stars through the telescope, this is what is known as "good seeing".

Transparency is a measure of sky darkness and the visibility of stars. Good transparency is when the sky is perfectly clear, free of any obvious cloud, haze or pollutant, whereas things like fog, dust, smoke, high clouds, haze etc will reduce the visibility of stars and such a situation is referred to as poor transparency.