Dithering and PHD2



The user guide for SGP says that in order for dithering option to work “PHD Server” must be enabled through Tools menu. I don’t see that option in PHD2. Could it be this part of the SGP manual requires updating?



The PHD server can be Enabled/Disabled under the “Tools” menu. The server allows SGP to send and receive messages from PHD. You should turn on dithering in SPG and not in PHD.


Dithering is a function only available in SGP because it is the imaging
software, so I have no intention of attempting to activate dithering
through PHD2. I cannot find PHD Server under “Tools” menu in PHD2 or in
SGP. I am assuming it needs to be found in PHD2. And now that I attempted
to screen capture it I do find it in the Tools dropdown, and it is already

[image: image.png]


In PHD you need to have Enable Server checked as shown in your screen shot. You also need to select your dither pattern. I like “spiral”.

Actually, PHD can do the dithering. Your imaging software can send a “dither message” to PHD and let PHD doing the dithering. The imaging software that comes with Atik cameras can dither this way. In SGP, the dithering is turned off in PHD and SGP does the dithering.


Yes, what threw me was the phrase “PHD Server” put in quotation marks so tightly that I thought I would be seeing the exact phrase. Then I saw the “Enable Server” instead.

I haven’t seen dithering options in PHD2, but I will look for it. If they both are able to dither I would prefer to leave it to the imaging software than to PHD2 whose job is guiding.



Here is a a stack of dithered images that have not be registered. You’ll see some hot pixels. When the stars are registered the hot pixels disappear. I know you know this, but I thought I’d share.


Dithering involves both the imaging app (SGP) and the guiding app (PHD2). Only SGP knows when to dither (between subs), and when the time is right SGP commands PHD2 to dither. PHD2 responds by moving its lock position, guiding the guide star to the new lock position, then reporting back to SGP that the dither is done and that guiding has settled.



So in reality there isn’t a choice in which software we depend on to initiate dither - SGP initiates it and PHD2 does it.



yes, exactly.

(The exception is when you have Guiding Interface = No Auto Guider in SGP (unguided imaging), in that case SGP does the dither itself.)


Is there any productive way (through settings) to speed up the process of dithering and recovering from dithering. When a sequence has been created - the estimated time of the sequence is featured. But I need to multiple that by 1.32 which get’s close to the real time as I have to factor in the “TIME” for dithering. I elect “extreme dithering” but doubt this has any bearing.