How often do you refocus

[iwols]

Hi after years of focusing  and using that setting for the session  on every filter I've realised that I neeed to refocus more often as well as every filter, just wondered what you do.. Thanks 

[scotty38]

I focus at the beginning of a session using the UVIR filter and then have focus offsets for the others (only one in my case as I have OSC) so the focuser moves if filters are swapped. I then have my session set to refocus after a flip and again if the HFR and/or temperature changes by a set amount.

[raadoo]

I don't have a temperature sensor (yet?) so I've set my EAF to refocus every 30min. Takes about 3 minutes for the focus routine to run and then it's back to imaging, so I don't feel like I'm losing that much time. I haven't had any problems with this approach, yet, and there have been quite a few nights when the temperature dropped significantly throughout the session.

[tomato]

I still tend to be in  attendance during an imaging session so keep a close eye on the FWHM trend line as the subs come in. If it starts to trend up and sky conditions remain unchanged which I can check by looking at the guide star stats, then  I will refocus. It depends a lot on the elevation of the object and the orientation of the scopes, as well as how steady the ambient temperature is.

[bottletopburly]

Using Apt  and focussing using inv power it’s constantly checking focus value and adjusts to suit so haven’t bothered fitting the temp sensor on my Deepskydad auto focuser.

[Fegato]

I use NINA, and with the advanced sequencer you can set it to refocus on the basis of a % increase in HFD. In theory this should be much more efficient than just picking a random time period or even a specific temperature change. I've not been using it long, but so far so good.

[Adam J]

Only if I see a change in HFR or I change a filter. Or I don't like the focus curve I got. 

[david_taurus83]

Also with NINA, set to focus if change in temperature or of HFR increases 10%. Also set to focus every couple of hours. The faster the f ratio, the fussier it will be. My Redcat is very fussy. Only a couple of steps out of focus is enough for a 0.3 HFR increase.

[Clarkey]

25 minutes ago, Adam J said:

Only if I see a change in HFR or I change a filter. Or I don't like the focus curve I got. 

Same here.

[carastro]

I check focus at the beginning of a session and check all filters. Generally most are parfocal but I do find this can vary with the temperature.   I then set up a sequence with all the filters that are of the same focus and if any are not I refocus at either the beginning of a session or the end and do them separately.  I do not have an autofocusser so have to do it manually,

Carole