Late-October evenings are great for skywatching. The nights are fairly long and cool. And there’s a lot to see. The Summer Triangle is still high in the west, and Taurus is climbing into view in the east. And this year, three planets are visible before midnight: Venus, Saturn, and Jupiter.

One thing that’s not visible for the next few evenings is the Moon. It doesn’t rise until the wee hours of the morning. So if you can get away from city lights, you should be treated to a beautiful view of the stars.

Dark skies are especially important for astronomers, allowing them to see deeper into the universe. But other things can limit the view. That includes clouds – not just on Earth, but in the stars.

Dust is sprinkled between the stars. And the farther you look, the more dust gets in the way. That obscuring effect is known as extinction. Astronomers have to account for it when they measure an object’s brightness, its color, and more. In some cases, they’re looking through a fairly uniform scattering of dust. But in others, they’re looking through dense clouds, which make it really tough to see what’s beyond.

Another concern is called seeing – the stability of the atmosphere. If the air is calm, the seeing is pretty good. But if it’s turbulent, it smears the view of the stars. Bad seeing makes the stars twinkle more fiercely. That’s a beautiful effect for casual skywatchers, but bad for astronomers.

Script by Damond Benningfield