I recently added filters to my setup. In the Filter setup dialog there is a section for Focus pt per filter. Is this a starting point for auto focus to run on a filter? Or is this a firm focus point and auto focus won’t run other than set the number I put in the field. I’m hoping it is a suggested starting point. It would definitly speed up the process per filter.
The “Focus Pt” in the filter setup is not a firm focus point. It is a relative number used for autofocus when utilizing “Focus with filter: X” and “Auto adjust focus per filter”.
This means that when you run autofocus, the AF routine will switch to your focusing filter (usually LUM) and focus on that filter. Then, when the filter wheel moves to another filter, it will move the focus the relative difference in focus point between those two filters.
For example, let’s say in the filter setup window you have 10,000 set for the LUM filter, and 10,100 for the RED filter. You run autofocus. The filter wheel changes to the LUM filter and focuses. Then the filter wheel switches to the RED filter and moves the focuser out 100 steps. 100 is the relative difference between the Focus Pt of the LUM and RED filters.
In order for this to work you would need to carefully measure where the LUM filter comes to focus and then focus through the RED filter and see where it comes to focus. You need to focus through all your filters and determine the filter offset - the difference in focuser steps between where the LUM filter comes to focus and where all the other filters come to focus.
So I don’t run auto focus on the filter I’m about to use? Or is the method above a time saving thing? I’m just trying to understand. Thank you
Using filter offsets is a time saving thing. When you focus through narrowband filters it takes much longer exposures (30s-1min) to get good stars to measure the focus. So if you run autofocus on your narrowband filters it can take 6-10 minutes to run autofocus depending on your download times. If instead you measure your filter offsets once, then you can use the LUM filter to focus all filters, using 5s exposures and it takes about 2 minutes to run autofocus.
Of course you can focus through each filter if you want to. In that case you don’t need to do anything in the “Focus pt” dialogue of the filter setup window.
Thank you. This is exactly what I needed. I appreciate your time.