SharpCap Forums

Hi Robin,

My Details:
Version of SharpCap : 4.1.12196.0
Focuser : Pegasus FocusCube3
Computer: Windows11 Pro Ver. 24H2 (OS Build 26100.6899)

When I select Automatic Focusing the process often appears successful, a curve is fitted showing the best focus position and the focuser moves to that position but the images are clearly still out of focus. I presume this must be a backlash problem but I can't work out what.

I have selected "Handled by Sharpcap Amount 500 Steps" in settings.

The refocus log (sorry, I wasn't able to save it but I have attached pictures below) includes a line which sets out the refocus parameters which includes this :
"....allowing for backlash of up to 0" so it seems to be ignoring what's in settings.

Getting Automatic focus working reliably would be a big step in the right direction for me so I hope you can help.

Kind Regards,
Tony

Hi Tony,

to be honest, the best bet is to switch the focus backlash handling from 'Handled by SharpCap' to 'Overshoot'.

For the 'Handled By SharpCap' option, you need to precisely measure the amount of backlash in your focuser by scanning in both directions and finding the difference between the two best focus positions. Then you have to hope that the amount of backlash is constant (and doesn't change for instance as the orientation of the telescope changes the way the weight of the camera bears on the focuser). If all of that is correct then it will indeed go to the right position, but if the amount is off then the movements during and after the scan may be off.

In 'overshoot' mode, all you need to do is ensure that the number you choose for the overshoot amount is *bigger* than the backlash amount of the focuser - there is no need for the value to be exact. SharpCap will always try to move the focuser in the preferred direction, and when it does need to go the other way it will first go back an additional amount to then approach from the preferred direction.

I'd also suggest updating your version of SharpCap - the one you are using is nearly 18 months old now and there have been lots of improvements and bug fixes since then.

cheers,

Robin

Hi Robin,
Thanks for your reply. I'll do that next time I get the chance and load the latest version now.

Kind Regards,
Tony