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PHD2 dithering - random or spiral?

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As per the title, which should I choose? What makes one preferable to the other?

Imaging at 1.05 arc-sec/pixel, guiding with a 240mm F4 scope and QHY5-II.



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Yes I concur with random. Out of the box PHD2 has it set like that. Most, if not all, of the default settings work well.

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Always worth looking at what the PHD2 Instructions say:

'Random mode' - tells PHD2 to use a random-number generator to compute both the size and the direction of the dither, subject to any constraints imposed by RA-only mode or by the Dec guiding mode being set to 'None'.

'Spiral mode' - tells PHD2 to dither with fixed-size amounts in a clockwise spiral pattern.  This can be a good choice when the imaging camera has significant fixed-pattern noise or the mount has a troublesome amount of Dec backlash.

I don't know how far you want to dither, your guide image scale is 4.47arcsec/pixel, so a setting of 3 in PHD2 will dither the image camera about 13 pixels.


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Thanks Michael.

I had read that info in PHD2, but in truth, didn't quite understand it. Your info re the setting and dither amount is interesting though, and is something for me to check, and have a play with. 🙂


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