Why on some clear nights do we see more stars than others?

Stargazing is both romantic and educational. Unfortunately, even with careful planning, sometimes the night is not as star-filled as you would hope. Ultimately, certain factors will compete with, or block out, the shining light of the stars.

In order to see the stars, the sky needs to be virtually cloud-free; if rainstorm clouds can block the Sun then light fluffy clouds will easily be able to block a star‘s light. Star Trails at Bowsprit Cottage by poplinre, on Flickr

Providing there are no clouds to block your view of the stars, the next issue is light pollution.

One source of light pollution is obvious: the light from streetlights, lamps in the living room and so on. If you live in a city or a suburb it is noticeably harder to see as many stars because of ’skyglow’. It appears as if there are fewer stars, but in reality, you just can’t see them because the light in the surrounding area illuminates the sky, competing with the light of the stars. It is a good idea to travel to places far away from the lights of cities and towns

Another source of light that competes with stars is the Moon; this may explain why stars appear dimmer on certain days from the same location. The Moon is the second brightest object in the sky after the Sun. A full moon will reflect light from the Sun and interfere with your ability to see the dim light of the stars.

Also bear in mind that it takes 20 – 30 minutes for your eyes to fully adjust to the dark. If you have stepped out from a brightly lit area, or a car has just passed by, it will take time before you can fully assess how visible the stars are. Serious stargazers use red torches/flashlights to minimise night blindness when they need to read or navigate their way around.

Your best bet to see the most stars would be a clear night, during a new Moon, far from any man-made source of light. It also makes stargazing more romantic when you (and maybe a significant other) are the only people staring up at the night, far away from civilization.

In fact, July is going to be a month full of ‘stargazery’ wonder. It’s like you’re meant to go stargazing!

I best not find you stargazing in my spots though.

Answer by Lucy Huang

Question from Caera McCallion via Facebook.

Article by Lucy Huang

July 3, 2013

Lucy is Guru Magazine's intern; a recent graduate from Skidmore College, NY she has a background in molecular biology. Passionate about killing the jargon from science, she likes drinking tea so much that she sells the stuff in a posh shop.

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