Filter offsets

General
1

Hello,

What’s the best way to accurately determine filter offsets? I’ve tried in the past but I guess I didn’t spend enough time on it as the results weren’t great and I moved back to focusing on each filter.

I’m keen to get this nailed down in time for the darker nights, so I know the next couple of months is the time to get it done.

My thoughts are to create a sequence using all the filters with say 1s exposures, focus on filter change enabled and rotate through events. Am I right in thinking this will give me a bunch of autofocus plots for each filter and if so am I able to ignore temperature shift through the evening?

Should I get exactly the same offsets between my frac and newt, or do I need to analyse both?

If my thinking’s correct here how then do I get the offsets from the log?

Thanks,
Ian

2

Hi Ian,

You can use the AF Logviewer to analyse the logs, see the thread here: SGP AF Logviewer v1.2 Release - Auto Focus - Main Sequence Software

If you scroll down in that thread you’ll see an example of what you just described, a sequence of many AF runs using different filters. You provide the logviewer with that logfile and it should compute the filter offsets. If there is a significant change in focus postion with temperature it will also compute that temperature coefficient.

Mikael

3

Thank you Mikael, this is great, I’ll have a good read through and hopefully get my offsets figured out and validated in the coming month.

Great work!

Cheers
Ian