Filter offsets and runs

[Onimusha]

Hi all,

Since im tired of refocusing all the time I ended up with the topic filter offsets. I do have Focusmax V4, Lakeside Astrofocuser and MDL.

I was thinking about how to proper find out the filter offsets:

1. I had in mind that i should first do 1 Run FM4 with the Luminance Filter --> Notice to focus position i.e. 2050
2. Switching i. e. to H-Alpha and then do 5 FM4 runs --> Average the values (i.e 2020,2030,2035,2025,2040 --> 2028)
3. Filteroffset for H-Alpha to my Reference Filter Luminance would be then 2050-2028 --> 22
4. Lets assume Procedure 3 (above) has taken 1.5 hours. Now I want to do the same for OIII Filter. From my experience i need to refocus now Luminance and do the same for OIII as done under Point 3 with H-Alpha right?  I come to this conclusion because in my Area the temperature drops for example by 4 C often or the atmosphere has changed so i need to do a refocus of Luminance to be in focus again to start over with OIII offset measurements. Is this the correct way to do it?

Thanks for you inputs. 

Francesco