Thank you. The offsets are only used in Voyager Array where focusing for each array (imaging unit) is done with a single filter and then other filter positions are offset to achieve best focus. So for Array 1, I have the L filter as “master” for focusing and all other filters on that unit (Ha, OIII and SII) are offset from whatever best focus position is achieved with L. For Array 2, I use an OSC camera so by default the colour grid is focused at once. If I were to have R,G and B filters on array 2, I would perhaps use R as “master” and offset B and G.
When I used MaxIM in the past (from 2002 until I started using Voyager), I always used offsets for my filter wheel. Having a refractor with a relatively stable relationship between T and filter position, it wasn’t difficult to achieve acceptable focus for other filters.
As Voyager is so fast focusing, even in narrowband, I moved away from offsets when imaging with just one unit. Now that I have two scopes in tandem and am using Array, I have had to recalculate offsets and use them once more. I know Leo is not keen on offsets and has been looking at other ways of focusing in Voyager Array but so far my results are good enough for the seeing I get in the UK.
Offsets are entered as numeric values relative to the zero L position in the settings menu of Observatory Array in Voyager Array - a window that is visible to those using that version of Voyager.