Dithering doesn't seem to work (SGP 2.6.0.23 and PHD 2.6.3)

Hi there,

Recently I upgraded my software package, see title and now my dithering doesn’t seem to work. I’m not sure what went wrong and also can’t seem to find anything useful in the logs either. I’ve attached the truncated logs to this post as a zipped logs folder was still a bit too large: logs.zip (494.4 KB)
. Hope someone can help me :slight_smile: .

How do you know that dither is not working? The logs show it happening so, at face value, I have no reason to believe it’s not. I do see that your dither magnitude is set to “small dither”. Might be too small.

Last night I’ve been changing up a couple of settings, Extreme dither, and settling time set to 5 seconds. I’ve been watching between frames a bit but notice that SGP starts integration immediately. I also notice in PHD that I don’t see a “dither” part on the “timeline”. I did see this before in PHD. In PHD I use the “spiral” option so between frames I should see some spiral action between frames. I checked the results with the Blink tool in PixInsight this morning and notice that I don’t see any spiral action. That’s why I think there’s something wrong.

@zwik

Hmm, OK, Can you share the sgf file you were using so I can take a look at that?

Hereby the sequence file.

ngc2403.zip (229.9 KB)

@zwik

That sequence, overall, seems OK. It does use a small dither (which may not be noticeable depending on your rig). Additionally, it makes no attempt to settle. From SGPro everything looks normal (I think). Sequence looks good, logs indicate that a dither request is made. Next step is to look at the PHD2 debug logs to see what it’s doing once it receives the request.

Logs for PHD can be found in the first post. it is truncated but I think it is enough to see what is going on. Thanks for all the help so far Ken!

@zwik

I’m sorry I can’t be of more help. On paper, everything looks fine. PHD2 gets the dither request and seems to execute on that with no error and then eventually reports it is done. A couple things:

  • I am not familiar with dither spiral. What happens when you don’t use this?
  • Looks like you might be using “on-camera” guide commands. Any reason you are not using ASCOM? If everything is happening, but nothing is moving, I would start looking at connections to the mount.

I believe that the spiral dither here is the problem because each dither move will be very small as it unwinds in a spiral from the start location. All dither moves will be the same, very small amount - but over time the full dither pattern will slowly expand outward.

I think that the main need for dithering is to reduce the impact of pattern noise - so I would use random dithering instead. Then all the moves should tend to be much larger and more noticeable in the logs.

Frank

In the meanwhile I’ve been testing a bit. I’ve created a new sequence, and used extreme dithering and a 5 second settle time as settings in SGP. In PHD I still have selected spiral dithering. Now when I start the sequence. I’ve also set these settings in another, older, sequence. I’ve been running these sequences and I see dithering happening in PHD, in the graph log, and I don’t see it in the other. So it seems to be a problem with the older sequence.

So I’ve recreated the older sequence and now all seems to be working fine again :slight_smile: .