SharpCap Forums

Hello!
Not sure if this makes a big difference in the final image but according to my Drift Graph, the XY dithering pixel movement seems to regularly exceed the 1 pixel Max Dither Step that I've selected. If I've correctly interpreted what the graph is telling me, some of my dither steps shift the next starting point 5, 10 or more. Other times they are within the 1 pixel range.

My other dither settings I believe are the SC defaults...Settle Threshold, 2 px....Min Settle time, 5 sec...Max 30 sec.

If possible, I'd prefer not to have such radical pixel movements as they're not needed to defeat any issues with walking noise. Is there some interaction with PHD that is contributing to this or could my mount's reaction to the dither command be greater than the limit due to backlash or something else?

Thanks!
Craig

Hi Craig,

I just had a play and the entries I see in the PHD log seem to match the dither sizes selected in SharpCap - for instance when I set 1px, I see things like this in the PHD log
When I set a higher dither size in SharpCap, I get bigger values for the 'dither by' adjustments.

Do you see anything in your PHD log that looks wrong in this sense?

The only other thing I can think of is that PHD has some 'Dither Settings' at the bottom of the Advanced Settings dialog (first page). One of them is 'Scale' - is it possible that this has been turned up in your config?

cheers,

Robin

I'll take a look. Thanks Robin!

Craig

Hi Robin

I checked several PHD log samples and didn't see anything out of line."Dither by" in one sample was 0.997, -0.109 and the new lock position was not radically moved. None of my dither samples were over .999. Also checked the PHD Dither scale and it's set at 1.0. Nothing obviously out of place that I can see. I guess it's still a mystery why the SC Drift Graph sometimes shows more XY pixel movement than that.

I guess I'll pose the question to the PHD group to see if they have any ideas. Thanks so much for looking into my question Robin!

Best Wishes,
Craig

Hi Craig,

sorry, I think I understand now - you were talking about the SharpCap drift chart showing bigger jumps than 1 pixel - I thought you were talking about the PHD2 graph.

Remember that the pixel scale is different between the guide scope (PHD) and the main scope in SharpCap. The dither size in pixels measurement is in terms of pixel scale for the guide scope.

If your guide scope is 200mm and your main scope is 800mm then the main image will move 4 pixels for every pixel moved by the guide image (assuming the same pixel size on the two cameras).

cheers,

Robin

Hi Robin...

Of course! Sorry, didn't even think about the scale difference. Thanks for indulging me! If it'll let me, I'll experiment with the PHD Dither scale setting to see if I can limit the movement further...I have a 162mm fl guide scope.

Best wishes,
Craig