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Ceph and Cass

whats 'dithering' please?


Gasman
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One answer it's a technique where the mount is moved slightly between exposures... by doing this hot or cold pixels will end up in different positions when the image is stacked and their effect be reduced but useful signal will be reinforced...

Peter...

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One answer it's a technique where the mount is moved slightly between exposures... by doing this hot or cold pixels will end up in different positions when the image is stacked and their effect be reduced but useful signal will be reinforced...

Peter...

Sent from my GT-P7300 using Tapatalk 4

This is 100 percent correct. Look up dithering in the PHD Guiding manual. I bet there's a definition in there, or at least an explanation in an article written by Craig Stark. Either way, your description is correct.

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One answer it's a technique where the mount is moved slightly between exposures... by doing this hot or cold pixels will end up in different positions when the image is stacked and their effect be reduced but useful signal will be reinforced...

Peter...

Sent from my GT-P7300 using Tapatalk 4

Precisely this. The software used to control the camera tells the guiding software to stop guiding, it then instructs the mount to move slightly in RA and Dec and then instructs the guiding software to resume guiding. The idea here is what Peter said - your object will land on a different part of the CCD sensor in each and every exposure. Once you register and stack all your exposures, the object will be in the same place but the hot and cold pixels from your CCD sensor will be in different locations, so averaging during stacking reduces their effect. It's a pretty good technique that I use every time I go out imaging. Nebulosity and PHD Guiding, by the same author, are excellent for dithering as they communicate perfectly well.

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Is dithering just a technqiue to detect rogue pixels or does it allow integration and alignment applications - if so coded - to reinforce good signal elsewhere as well? How does the software "know" the picture is dithered? By watchign the movement of the duff pixel?

This is my next thing to try. I so,so,so,so wish Artemis capture included the ability to dither combined with PHD..... :(

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In my understanding, dIther on its own just redistributes bad pixels, which is far from unimportant. If used in conjunction with drizzle it can detect sub pixel resolution, which isn't unimportant either! Most important of all are the limits of my understanding...

Olly

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