30 Sep '11, 5pm

Why do stars appear in the background of some images and not others #NASA

Vishnu, an Earth Observatory reader, posed a great question after viewing “The Six-Million Mile View of Earth and Moon “: “I’ve never seen a photo like that. Was the background beyond Earth ‘photoshopped’ to remove background stars, or is that angle so narrow and the background space so coincidentally ‘empty’ that no visible stars are there to be seen?” Our colleague D.C. Agle from the Jet Propulsion Laboratory worked with the Juno science team to provide this answer: “The exposure time for the image — it’s actually three images: red, green and blue — was too short for any stars to be seen. Earth and the Moon were bright enough that a short-duration exposure was all that was needed. The brighter an object is, the shorter the exposure time required to capture an image of it. It’s similar to why you don’t really see stars in Apollo photos from the moon – the subjects being p...

Full article: http://earthobservatory.nasa.gov/blogs/earthmatters/2011/...

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