Optimal Dithering settings

Does anyone have any experience on what dithering settings are optimal for a focal length of about 1000mm?

I have TEC 140 APO which is 980mm focal length. I imaged M13 last Saturday night with QSI660wsg and used OAG with Superstar autoguider. Both camera and autoguider have same pixel size so both have same image scale.

My dithering settings were High Dither and Settle < 0.5 for 3 seconds with PHD2 interface and worked well. Be patient, sometimes dithering takes a while (maybe up to 2 minutes) and other times takes a few seconds.


As Peter is alluding, the guide camera needs to be taken into account here as well.

What’s the sampling on your guider and your imager? You want to move at least a pixel on the imaging camera for each dither (I would actually suggest 2 or 3 pixels). Really you probably want to move a couple of pixels on the imager. But since the dither is done via your guide camera we need to know how those two relate to one another.

For instance if you’re guiding through an OAG you’ll need a much smaller dither than if you were dithering with a 50mm guider. In all honesty the movement amount could be the same but a “Small” dither through the OAG and a “Huge” dither through the 50mm could both move your imager the same amount.


I am using an OAG (Lodestar) on an 1100mm f5.3 RC8’’. I am testing as we speak with the above suggestions…I think that even extreme dither is not bad!