”Earth Shine,“ multi-exposure image of the moon from a Boing Boing reader




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My god! It’s a giant sphere of rock just floating in the sky!


No, wait… it’s falling!

It’s falling around the Sun…

… and so is the Earth!


*hugs plushie


That’s No Moon.

//so sorry…


The rock is mooning us.

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Big deal anybody can take a picture of the “light” side of the moon…

Light side of the Moon… is made of low-fat cheese?


For readers that haven’t explored current astronomical image capturing methods: image stacking is a standard technique whereby multiple shorter-time exposures of an object are stacked together mathematically to give the same effect of one long-time exposure. For example, a hundred 1/10 second exposure can give the same as one ten second exposure. The image-capturing device, of course, has to have very low noise.

Astronomical objects aren’t stationary, from the telescope’s point of view and it’s very difficult to track the object precisely over a longish time. In addition, the Moon has to be tracked at a slightly different speed than the background sky.

Mind you, exposure times for the Moon are generally short, daylight range.

Not necessarily. The noise from measurement to measurement both adds and subtracts, due to its random nature. The signal only adds. By adding together many measurements (whether it is a NMR spectrum acquisition or a photograph), the signal grows out from the noise even if it would be completely obscured in a single measurement.

Edit: The noise itself can be pretty handy, too. It can be used for increasing the effective resolution of the sensor past its native resolution, and catch signals below its sensitivity. Counterintuitive as it can be, noise is not always The Enemy.

Here comes the advantage of many short exposures over one long. You can use software for feature tracking, and register the slightly different images and morph them a little before stacking. You can also detect and throw out the ones where the atmospheric turbulences added a little bit too much of distort.

See also additional tricks possible with lucky imaging.

Not if Arnie gets his way:

But is it a planet or a star?

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