Autofocus and Backlash weirdness

[nexusjeep]

Hi Robin,
The Autofocus is now working with the extra points but I have a slight issue with backlash in the Autofocus routine, in sharpcap if I look at the focuser currently it is selected to none for backlash as per the image below.

Focuser hardware.png (10.86 KiB) Viewed 402 times

When I run the built in Autofocus script it is moving the focuser for a backlash compensation of 50,000 steps before moving it back in so moves out to 384351 then to 334351 and then starts sampling the script box displays the information below.

Starting :

Starting : Refocus using the same settings as the most recently used autofocus run

Info : 'Refocus scan configured to use Multi-Star FWHM Measurement for scan about 311851 from 334351 to 289351
using 10 steps of 5000, 2 samples, allowing for backlash of up to 50000' while running step Refocus using the same
settings as the most recently used autofocus run

Starting : Autofocus between 334351 and 289351 with 10 steps allowing for backlash up to 50000

Info : 'Focus scan between 334351 and 289351 in 10 steps of 5000' while running step Autofocus between 334351 and 289351
with 10 steps allowing for backlash up to 50000

Info : 'Moving focuser to end position : 289351' while running step Autofocus between 334351 and 289351 with 10 steps
allowing for backlash up to 50000

The actual focus run works fine but not sure where the massive backlash amount is coming from, I did try to set the backlash by sharpcap option and leave it at 0 or 1 but if I select it the Apply / OK box at the bottom of the hardware tab remains greyed out so I cannot save the change.

Cheers
Nick

[admin]

Hi Nick,

I think the backlash allowance comes from one of the 'autofocus' steps in the sequencer or deep sky planner - those let you specify the backlash allowance and store the value used if the focus scan is successful. Unfortunately, if you use the focusing tools manually, the backlash allowance may not get set (or overwritten), so the large value used in the sequencer remains.

So, probably the solution is to run a one step sequence to autofocus with the desired settings (including a smaller backlash allowance), which will then save those settings. The allowance is how far SharpCap deliberately overshoots the start position of the scan (and the start position when returning to the best focus point) to ensure that any backlash has been cleared before scanning.

cheers,

Robin

[nexusjeep]

Cheers Robin,
Will Create a sequence for future use if it ever stops raining and we can see the stars

Cheers
Nick