How does dither work in SGpro/PHD2?

Do I need to have SGPro connected to my scope in order for dithering to work when I’m using PHD2? In other words does SGpro instruct PHD2 to do the dither or does SGPro actually need to move the scope its self?

I failed to get dithering to work last night although SGpro recognised it was running and guiding and it said dithering was in progress between frames.

Also although I have all logging and server mode enabled in PHD2 I can’t get the PHD graph to display in SGPro.

Dithering is controller via PHD… so if you have ST-4 or ASCOM selected it should work. Make sure you select ‘Extreme’ dithering otherwise you might find that the ‘motion’ in your pictures is only a few pixels.

The way you can tell it’s working is that you’ll see spikes in RA/Dec right around the start of each image. If it’s doing that, you probably just have it set too low to notice it.

I’m wondering if this is due to where your PHD log is being saved. Ken or Jared will have to weigh in, but I think SGP reads the PHD log so perhaps SGP is looking in the wrong place for the log. Make sure that your PHD2 log is being created in your Documents/PHD2 folder. And make sure the guide log is active, not just the debug log.

Also, regarding the size of the dither, mads is right that you should see a spike in the PHD graph when the dither occurs. But you may or may not want to use extreme dither depending on your equipment. The larger the dither the longer it takes for the mount to settle and in my case I like to go with a lesser dither so it doesn’t take as long to settle after the move.

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Thanks for the replies.

I tried all levels of dither and had my eyes glued to the PHD curve but saw no changes when SGpro was displaying “Dithering”.

I’ve reset the PHD log file location to the default so hopefully I’ll see the graph in SGpro now. Is this a requirement for sgpro driven dithering to work as well?

What version of SGP and PHD are you using?

No, that’s only for the graph display and has no effect on dithering.


I got the graph working by setting the PHD2 log directory to the default expected by SGpro. DIthering is still an issue - although I have seen it work when I set the dither scale to 3 in PHD2 when it went extreme. Setting it back to 2 or 1 gave nothing! I will continue to play.

Thanks again.

If you could provide the version of SGP and PHD you’re using that would be helpful.

Also it might be worth posting the SGP and PHD log on dropbox for us to look at.


Sounds to me like a mount issue. How’s your backlash? Does it take awhile to settle?

Its all working tickity boo! Needed to set the PHD2 dither factor to 7 for my set up to give a nice dither.

Thanks for the help.