QSI 520c Betriebsanweisung PDF herunterladen (Seite 40)

QSI 500 SERIES USER GUIDE

Stacking Images

After calibrating each of your raw images with dark frames, flat fields and bias frames,

combining or “stacking” multiple sub-exposures can be used to further reduce the noise in

your images. Stacking multiple images with a pixel-by-pixel average or median combine

tends to increase the signal to noise ratio (SNR) of the combined image. This is because

random variations in pixel values tend to cancel each other out when multiple images are

combined, resulting in a smooth background, while non-random pixels, the bright objects in

the night sky you’re trying to take a picture of, reinforce each other getting you closer to a

true representation of the patch of sky you’re imaging.

The benefits of stacking images can be clearly seen by comparing an individual frame to a

pixel-by-pixel average of multiple frames.

Individual dark-subtracted image of M78

Average combine of 9 dark-subtracted images of M78

Averaging 9 separate images increases the signal to noise ratio of the final image, allowing

the faint nebulosity in M78 to become visible and smoothing the black sky background.

Adding more frames would further improve the results although you do end up in a situation

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QSI 520c Betriebsanweisung Seite 40