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06-05-2012
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Mars captured under strange seeing conditions

Submitter: Rik ter Horst
Description: Generally, when the wind blows and you see stars twinkling with the naked eye you wouldn't go outside to set up your telescope for planetary imaging, but for once I did and this evening has changed my mindů

This is a section of a Mars video, taken on March 22nd, with my 200mm F/25 telescope from Ewer, 25 km north-west from Groningen. The original AVI-movie counts a total of 5000 frames. At the end of the video you see the end result after image processing. Usually, seeing (air turbulence) causes blurring of the recorded images with better and worse moments so that only a small amount of frames can be selected and be stacked by shift-and-add for further processing. This technique is called 'lucky imaging'.

On this particular night I was very lucky: A high pressure area was around and although the images jumped up and down caused by a strong northern wind, each single frame was tack-sharp (only noisy caused by the Gain-setting of the camera) and all 5000 frames could be used. More frames mean less noise and more possibilities for image processing.

Obviously, on this night seeing cells were larger than the aperture of my telescope, so they had little effect on image quality. Usually, seeing cells are (much) smaller and will smear out details of images. This is the reason why large telescopes almost never reach their theoretical resolution and small instruments can occasionally outperform these optical giants ;-)

To conclude, when a high pressure area is around (good high altitude seeing), even windy conditions (ground layer seeing) can still provide circumstances useful for high resolution imaging.
Copyright: Rik ter Horst
 
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