I have been using the focus after 'n' minutes option since it was first introduced into the software and it does what it is supposed to.

Sometimes, I find the option is less than optimal and wondered if anyone had considered adding an option of focus after every 'n' images.

So, if was set to 20 it would focus at first as per normal then capture 20 images, refocus, another 20 images etc.

This would give me more flexibility as it would allow me to more easily control when it performed the focussing, taking some of the randomness out of the process.

Paul

This is not the answer you are looking for, but from my point of view, the best way to exclude such issues is to use the HFR threshold in the In-Sequence options.
So your HFR is calculated after the initial focus and you set the threshold. If the next HFR calculation exceeds the previous then an autofocus starts.

In addition to that, you could take the chance to look at John's videos www.youtube.com/@johneevans1 who is responsible for great things on the focus module

Euripides,

I have tried the focus on HFR settings in the past and found them more trouble than they are worth.

The focus routine takes some time to complete and sometimes it needs to repeat the process so it can be time consuming when it decides to do a focus run.

That is why I turned to time based focussing and after using it successfully, for a long time, I thought that having it controlled by the number of images would give me more control, but it is only a suggestion and thought I would put it out there for people to consider.

Paul

Hi Paul,

It could obviously be done, but currently the way the setup works is to set the refocus schedule for the sequence as a whole. So if had say:
30 x 1 min Red
30 x 1 min Green
30 x 1 min Blue
30 x 5 min Ha
30 x 5 min Oiii

and I set refocus after 20 frames then I would be refocusing every 20mins during RGB but every 1hr 40mins during narrowband (ignoring download time, dither time, etc).

Maybe this would be useful in some circumstances but would require adjustment based on each sequence.

In contrast with the time based approach, folks would generally pick a time period they are happy with, say 1 hour, and leave refocus unchanged as they use different sequences on different nights.

In case you aren't aware, in addition to time based refocuses, you can refocus:
- when temperature changes by X degrees C
- when HFR changes by a certain amount

Also, if you configure Adaptive Focus you can adapt focus per subframe as temperature or altitude changes.

When you say the time based approach is less than optimal could you explain that a little more? I'm aware that some folks prefer to refocus more frequently at the start of the night when temperature is changing more rapidly than later on, but by setting a combination of time based and temperature based refocuses they can achieve what they want (I think).

I've been there too...But I was losing so much precious time for focusing.

My current routine gives me 100% great focus, no donut-shaped stars (due to temp changes) and the Autofocus routine (maximum 1 minute) runs 3-4 times max, all night long (right now my sessions are 8 hours long).

1. First things first: Filter offsets. This is a game-changer for every mono user. If offsets are correct that saves us lots and lots of time.

2. Open up my observatory 1 hour before capturing time. That gives the required time for my gear to acclimate to the temperature.
indilib.org/forum/ekos/13682-suggestion-...autofocus.html#94833

3. After several nights of inspection, I know that my HFR is usually from 1.18 - 1.3. So I set my limit to HFR 1.25.

4. I set to check my HFR after every frame (my captures are 10' long). So if my calculated HFR is >1.25 then autofocus starts, otherwise the session continues.