Autofocus ran with wrong filter

I have just started using autofocus, so this is quite probably user error or at least me not using the system properly, but I am hoping that somebody will be able to put me on the right track. The issue is that autofocus ran on the wrong filter for my sequence. Here is what happened:

I was imaging the final sub of the final event for a target with the OIII filter and all was going well. During the sub the temperature dropped by 1 degree so autofocus was waiting to run as I have set it to refocus every 1 degree change. The sub finished and the sequence moved to the next target. It ran an auto centre routine, using the Luminance filter. It then did its autofocus routine, with the current filter, the Luminance filter. The first event of the new target was with the OIII filter, but that was slightly out of focus as the filters are not parfocal. What do I need to do to ensure this doesn’t happen again?

Is it something to do with setting an absolute focus value for each filter? That way when the filter changes from one to another the focus changes by the relative difference between the two filters’ stored focus values? Have I understood that correctly?

There is no log or sgf file attached here so I can only guess…

Seems like you have the AF routine set to focus with the LUM filter always. This is typical behavior, but for non parfocal filters it requires that you tell SGPro the delta (in steps) between focus of the LUM and O3 filters.

General info about AF:

Understanding how to set filter focus positions and AF filters:

Adjusting focus position when filters change:

Thank you for your reply Ken. Here is the log file:

I didn’t have AF set to run with the LUM filter, that happened to be the filter that was in place when the AF routine was called. It then moved back to the OIII filter to start the event, but I don’t yet have the focus delta info set, so it stayed in place.

Reading through the various help files (which are very helpful generally, so thank you for putting the time and effort into those!), it looks as though my best use of the AF system is indeed to set up the focus points for each filter, always use the LUM filter for focus and then the system can use the delta steps info to ensure that each filter is always in sharp focus when the filter change happens.

Fingers crossed!


I can’t be sure what happened… I looked at every auto focus event in your log and every single one of them is preceded by:

[07/09/2016 21:44:27] [DEBUG] [Camera Thread] Auto focus: setting filter OIII2

indicating that there were no attempts to focus with the LUM filter.

Ken, thank you for looking through the log and yes, you are correct, it does state that all autofocus events were carried out with the OIII filter set. The two instances of AF were as follows:

The first one after the move to the new target and the platesolve using the LUM filter:

[07/09/2016 23:35:22] [DEBUG] [Camera Thread] Auto focus is complete (best fit method: 1947; HFR 0.90)…

I thought that the focuser had moved more that I expected, so I stopped the sequence and reran AF and it did this:

[07/09/2016 23:43:21] [DEBUG] [Camera Thread] Auto focus is complete (best fit method: 1954; HFR 0.89)…

So, slightly curious as the log does suggest that AF was carried out with the correct OIII filter, but the two results are significantly different.

Anyway, my next task will be to fill all the Focus Point settings in the Filters screen and I will then use the LUM filter for focus and the delta settings info for when the filter changes. Hopefully that will give me consistent and correct autofocus in the future.

Thank you for your help.