{"id":48455,"date":"2023-08-07T12:16:53","date_gmt":"2023-08-07T12:16:53","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=120886"},"modified":"2023-08-07T12:32:37","modified_gmt":"2023-08-07T12:32:37","slug":"how-earths-atmosphere-affects-your-images-of-the-night-sky","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-earths-atmosphere-affects-your-images-of-the-night-sky\/","title":{"rendered":"How Earth\u2019s atmosphere affects your images of the night sky"},"content":{"rendered":"

The wobbles produced as starlight passes through Earth’s atmosphere can be a frustrating nuisance for astrophotographers. <\/p>

By Pete Lawrence\n \t\t<\/p>

Published: Monday, 07 August 2023 at 12:16 PM<\/p>

\n\n

If we lived on a planet without an atmosphere, we would certainly be able to capture clearer images of the night sky. Starlight would appear as sharp as our astrophotography<\/a> instruments are able to deliver.<\/p>\n

But since Earth does have an atmosphere, starlight wobbles as it passes through fast-moving regions of differing density and temperature \u2013 an effect known as \u2018seeing<\/a>\u2019.<\/p>\n

Over the course of a long exposure, the wobbles add up.<\/p>\n

\"Jupiter,<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Jupiter, imaged during bad seeing on the left and good seeing on the right. Credit: Steve Marsh<\/span><\/figcaption><\/div>\n

Atmospheric seeing is quantitatively measured by a value known as \u2018full width at half maximum\u2019 (FWHM).<\/p>\n

This value describes the highest resolution that you can expect to obtain on a particular night, if you take into consideration the interference introduced by atmospheric turbulence.<\/p>\n

The best observatories in the world can experience seeing with a FWHM value of 0.4 arcseconds.<\/p>\n

However, for the rest of us this figure is considerably larger and typically in the range of 1.5\u20134 arcseconds.<\/p>\n

High-resolution imaging, whether it\u2019s of the Moon, planets or deep-sky objects, depends on good seeing if you want to capture the sharpest detail.<\/p>\n

Lunar and planetary imagers use high frame-rate techniques to reduce seeing effects.<\/p>\n

\"Twinkling<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
Twinkling stars are an anathema to astronomers, as they are a sure sign of poor seeing. Credit: ESA\/Hubble & NASA<\/span><\/figcaption><\/div>\n

In the case of deep-sky astrophotography<\/a>, where long exposures are the norm, each element of detail will effectively be blurred by poor seeing.<\/span><\/p>\n

Seeing only really becomes a critically important issue if your goal is high-resolution deep-sky imaging \u2013 in other words, if you\u2019re taking close-up shots of distant deep-sky objects.<\/span><\/p>\n

For the most part, if you\u2019re taking wide-field images of large deep-sky objects, the effects of poor seeing aren\u2019t all that noticeable.<\/span><\/p> <\/body><\/html>\n

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