Sirius the Glitter-ball

 

A video of Sirius (the brightest star in the night sky) twinkling on the horizon, captured by Steve Brown @sjb_astro. Many people think they’re seeing a low altitude aircraft or UFO when they witness this.

This phenomenon occurs (to a lesser extent) with any bright star low on the horizon due to the vast amount of atmosphere you’re seeing it through. As stars gain elevation, and less atmosphere is between us and them, they shine more steadily, and views are hugely improved.

The difference in the amount of atmosphere you look through with elevation is very striking (as demonstrated in the sketch below).  Particularly for faint deep sky objects like galaxies, high elevations makes a dramatic difference to the quality of visual or photographic images you’ll collect.

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How much atmosphere you look through with observing angle.  At the zenith (overhead) you look through over 2/3 less atmosphere than at the horizon.

Night Shining Clouds

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A few weeks either side of the summer solstice is the best time to observe ‘noctilucent’ or ‘night shining’ clouds.

These wispy collections of ice crystals are the highest clouds on Earth, located in the mesosphere up to 50 miles overhead. They’re too faint to be seen in daylight and best observed when the Sun is between -6 and -12 degrees below the horizon.

At the moment at Highland latitudes this gives you an approximate window between 11.30pm and 3am in the morning.

Clear skies.