Increase maximum dither settling error


Re this thread:

The maximum setting for total error is currently 2.5px. According to Andy, that is an artifact from a limitation in a previous version of PHD. For those of us imaging at long focal length, 2.5px is not enough. For example, with my scope using the reducer at 2737mm and the QHY9, 2.5px corresponds to only 1" of total error, which is barely useable. Without the reducer, the settling feature is useless.

Another thing to consider, and that may merit some discussion, is the use of number of guide frames rather than seconds for settling time. The distinction is probably meaningless for those using a guide scope and short exposures, but at long FL using an OAG, guide exposures are often 3 to 5 seconds (sometimes more) for me. I generally like to see the guiding settle within the established error for 3 or 4 exposures. For a 4 second exposure, that would be a minimum of 12 seconds of settling time. If I change guide exposure (as I often need to do, particularly when changing targets) I need to remember to change the settling time accordingly. If settling time were based on a pre-set number of guide exposures instead of just a raw number of seconds, there would be no need to change settling time when exposure time changes.

This may be a moot point if number of guide frames is not available through the PHD2 API, but if it is, it may be worth considering. Thoughts anyone?



PHD2 does not currently support that. We could add it to PHD2 if you felt it was important and SGP was going to use it. For now I’d recommend setting the time limit to the value for the longest exposure you will use, e.g., 3 frames x 5 seconds = 15 seconds settle time. If you decrease your exposure time, you can still leave the settle time at 15 seconds.



Yes, this needs to be addressed and yes it is because PHD1 would report a max dither of 2.5 (any error >= 2.6 pixels was reported as 2.6 pixels).

I’ll add this into the 2.5.2 feature requests shortly.



Just FYI you can enter values in the drop down box for the pixel value. So you can enter different values, up to 100 pixels. Moving forward we’ll likely move this to a different control that makes this more obvious.