Best BIN setting for autofocus?

[SB]

Hi All
What is the most efficient BIN setting for quick and accurate autofocus routines? Bin 4 appears to result in a quicker and tighter focus but I am not sure why?

Comments much appreciated

Chris

[multiweb]

Depends how bright the star is and the exposure duration. I mostly use the default bin2×2 mode in Nebulosity with a baht mask.

[The_bluester]

In SGP and now Voyager I normally focused at 1X1 as I was using an OSC camera. It was a little slower in SGP due to the process to detect stars and it using the whole frame but I use the "robostar" focus routine in Voyager which centers the scope on a selected star then uses a small subframe.

The main advantage to binning during focus as far as I understood it was download speed, but the Voyager method using a small subframe largely negates that. The download is very fast as I think it is only downloading something like a 64 X 64 pixel subframe.