If you use the backlash compensation that is built in to Pegasus Astro (DMFC box), the internal backlash works fine when GOTO 0.
Using SGP Pro and IN + value e.g. 35, is also OK with GOTO 0.
Using SGP Pro and OUT + value e.g. 35, causes the count to become ‘Unknown’ with GOTO 0.
NB Pegasus Astro has a count that can’t go negative.
So, using SGP Pro and OUT + value e.g. 35 causes an attempt to initiate a move to -35 when trying to go to ZERO. Negative values are not allowed and the count is no longer valid.
Sequence:
Start with focuser at 0.
Backlash in SGP Pro set to OUT + 35.
Move out 1000 - is OK.
Move to ZERO - it fails and the count stays at ‘Unknown’.
Easy to see why when looking in the log:
[01/03/22 03:22:17.917][DEBUG][Focuser Thread][NONE] Focuser moving to 0
[01/03/22 03:22:17.922][DEBUG][Focuser Thread][NONE] Focuser backlash active, modified move to -35
Link to Logs
Useful Info
Backlash is only an issue for taking images. It can be ignored if the limts are approached e.g. to prevent hitting a physical end stop. Pegaus Astro has programmed limits e.g. a MIN and a MAX. It also won’t allow the count to be set to less than ZERO.
NB using (IN + value) goes the other way so isn’t an issue. There really isn’t a need to perform backlash when the move would go negative. It’s just to stop issues with hitting the end of the focuser and not for taking images, so can be skipped?
OS: Windows 10 64 bit Ver: 4.1.0.725 (latest beta) - I don’t have license (have used Trial for a week). Setting up camera - seems OK. Now setting up Focuser - get an invalid count when going to ZERO.
Is this an issue - when limits greater than the min/max get passed to the focuser when SGP backlash goes IN or OUT close to the limit? Causes the focuser to go to unknown.
Capping the lower end e.g. to not go below zero would be great, e.g. with backlash of 50 the lowest that the Focuser could be asked to move to would be 0 and not -50 when capped. Might want to check that the move to maximum can’t also be exceeded too?
I initially started with the Focuser operating in Reverse. That’s because my scope is marked IN @ 0 cm - OUT @ 9 cm and I wanted the count to also increase as the scale increased. It also meant that I had to Reverse the IN and OUT button movement. The most recent versions of the Beta don’t seem to like this and the count often doesn’t match what Count the Focuser (Controller) knows. IT works OK in other Apps. To avoid this I set the Focuser to OUT @ 8.75 cm and then 34,000 as a limit at IN @ 0.5 cm. This works better.
The issue I had was SGP would keep reversing the values in the ASCOM settings, so other Apps got confused. If the Focuser gets the count wrong then it also tries to pass the end stops and on my Focuser it can cause the mechanical link to weaken or shift or detach - not good.
The result is fewer reverses and a count that decreases until 0 when the Focuser is approaching the minimum extension. A by product is that the IN/OUT backlash doesn’t have an issue. Since I’m not looking at the scopes scale anyway this is better because SGP seems to have fewer issues. Of course everything should work e.g. not having to say which setup is preferred.