SGP and PHD 2 Issues

I have SGP and I have the new PHD 2.2.1 and SGP goes crazy everytime it tries to Dither. It would settle forever and never stop and doesn’t matter if its medium or small dither. There used to be an option for PHD 2 in settings but its gone now.

Perhaps I will try updating to the latest.

I love the new forum and hated Yahoo Groups since their changes.


Updating to the latest wouldn’t hurt.

Currently SGP isn’t using any special PHD2 features. The PHD2 and PHD1 implementation are the same at the moment, so there was no need to have a PHD2 option any longer.

Can you post your PHD and SGP log?


Where is the SGP log located?

If you go to the Help menu in SGP it has a link to the log folder. A log is created each time SGP is opened. You’ll need to correlate the SGP log to the PHD2 log.


The last time I had dithering on I noticed what sounds like the same thing. It took a long time for guiding to settle down after dither - a matter of minutes. So I turned off dithering for now and went on to other things.

I will try again soon and post the PHDLab analysis of guiding.


Right after I replied, I think I may have solved the dither problem for me (hope to find out tonight). In Control Panel > Auto Guide, I saw that it was set to Settle at 0.1 px. Since my guiding squiggles are less than 0.5 px, I set it to Settle at 0.5 px. and turned dither back on. I’ll report back as soon as I get some data.


I experienced a sequence failing to proceed after the autoguider failed to settle to the default 0.1px after a considerable time. On other occasions, it took perhaps two minutes to do so. It seems the default value of 0.1px just is not appropriate for some of us. Like Dave I changed the figure to 0.3 secs and all seems fine. Perhaps this has to do with seeing? Mine is lousy as a rule.

I’m not sure I have this totally right, but the settling distance is also affected by your focal length and image scale. If you are imaging with a long focal length scope you would want a lower settle distance. With a shorter focal length you could have a larger settle distance. This is because the image scale for a short focal length scope is more “forgiving” and settling at 1px will not affect the resolution of the image. For my TEC140 f/5.4 image scale 1.48arc/s I have the settle distance at 0.5px and it usually settles in about 10-20sec. I wouldn’t go with anything less than 0.3px. 0.1px seems impossibly tight to me.

Someone please correct me if I have this backwards.

I am not sure I understand. I have no idea how to setup PHD I only used the defaults and I got great results from that. And I also have defaults setup in SGP. I will have to google how to figure out the image scale with a 8" F3.9 with DSLR.

If the skies ever clear I will do some testing and report back.


The Wilmslow Astronomy web page has a section called useful formulae - on there you will find a calculator of image scale (CCD arcseconds/pixel). You will need to enter the scope focal length and the camera pixel size. Google “Wilmslow Astro” and you’ll find it. There is also a link to this site in the SGP online documentation.