Understanding and applying focuser backlash compensation

This video is about understanding and applying focuser backlash compensation. It is pretty much essential if you are to retain accurate focus during auto-focus routines as it makes an allowance for the mechanical play within the gearboxes making up the focus train.

[@astronomynotebook]

You have explained it so well...cannot think of doing astronomy without the wonderful tutorials on RUclips

[@llamarvasquez1803]

Hello there sir! how did you get 43 steps from 3 steps? I got lost thanks

[@SuperNova-py1ec]

Hi. Do you have any suggestions for measuring backlash on a SCT?

[@ahmedrizwankhan]

Awesome video as usual and very nicely explained. I am very interested in the methods used to find the backlash compensation in particularly the part where are you racked the focuser draw tube out by one marker and then started to bring that in. So it took 3 steps for the marker to disappear in to the draw tube. So your backlash would've been 3 steps?

[@simplifiedastro2092]

Hi Ahmed. Thanks for that.
No I actually had my step size set on 10 steps here as the resolution is relatively high. This meant that each movement was 10 steps. If you look at the SGP screen shots you will see that my backlash compensation setting was 40. This is made up of the 3 lots of 10 steps to get the focuser clearly moving, and I then added 10. It doesn't really matter what the number is, it will just take longer to get to the point of clearly seeing movement with a higher number, so it is easier to use 3 movements of 10 steps, than 30 movements of 1.
If your focuser is lower resolution you can use 1 or 2 steps, or on higher resolution you can increase this to whatever figure shows clear movement.
As noted, it isn't that critical as you are looking set the backlash figure at more than this, but naturally need to have a base figure to know what to put in, so this is about getting that base figure.
The resolution of your focusing train is the key thing as, depending what this is, you could be programming in 20 or 200 in SGP, and this could make the difference between it working or not. By way of example, my Lakeside/TS 80 needs to be set at 40, but my SestoSenso/Feathertouch is set at 200 as the focuser motor connects to the micro focus shaft so immediately has a 10x resolution.
Hope this all makes sense.

[@ahmedrizwankhan]

@@simplifiedastro2092 makes complete sense and thank you for taking your time in explaining this in further detail. Yes I did notice that you had backlash compensation set to 40 and then I wondered maybe this setting is for another scope. Makes complete sense.
It's always good to know the answers to some questions rather than blindly use "Yeah just use 100 and you'll be fine as long as it's more than the actual backlash" but I always did wonder how to find that magic number.
Appreciate your quality video once again and keep up the great work here mate.