Autofocus and default filter

I want to used lum filter to run autofocus when doing RGB and use the offsets. But despite having the box checked in the settings, the AF run uses the filter currently in the slot. Oddly, I plate solve with the lum filter and it has no problems switching from RGB. Am I missing something simple here? Thx

We need more info. Where exactly are the “settings” you are referring to?
Control panel in the sequence? Equipment profile? Posting a log would be
even better…

I’ll run a log off when I get home, but pretty sure I’ve got the right box ticked to use Lum as the filer. Attached. Thx

Well, that shows the setting in the equipment profile, but not necessarily
in the actual sequence control panel you are using. You may or may not
know that equipment profiles and sequence control panel operate somewhat
independently. I can explain that further if you need.

For now, go into your actual sequence…control panel/focus/autofocus
options and make sure the same setting is enabled there.

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Also check the settings in your filters set up in the Filters section of the Equipment Profile and Control Panel.

You need to set Lum against each filter. If ‘default’ is selected for the Red filter, the Red filter will be used for AF rather than the Lum filter.



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Thanks, Barry. Bullseye. That’s where I’ve been going wrong.
Clear skies,

Hi Barry, Happy New Year and apologies for picking up this old thread, but I’m struggling to understand how offsets work if autofocus is always using the L filter and not the intended RGBHa, etc. So am I correctly understanding that the autofocus will select L then once focus point is determined it then moves to correct RGBHa filter then adjusts for the calculated offset WITHOUT running a new autofcus on the selected filter. Currently I have my filters set to ‘default’ and autofocus runs on the selected filter, but I’m getting some weird results if the seeing is poor and/or when imaging at low altitudes. If I rerun the autofocus it then starts even further out of focus rather than previous focus start point and sometimes I just have to abort and start over…
TIA, Geof

Yes, you’ve got it Geof.

It’s important when measuring the offset for each filter that you run AF when the temp is stable and the scope is well equilibriated. Run a few curves to test the reproducibility of the offset. For NB filters you’ll need to allow about 45s for each data point. The process takes some time but once done, you’ve set offsets permanently for each profile.

Thanks Barry, that sounds great. I’m mid process swapping over from my C14 to my TSAPO100Q (4"), which I started a couple of weeks before Cristmas, but I only got my L focus point established when I lost the sky to cloud. I haven’t seen a clear sky since, other than last night, but with 40mph winds I wasn’t going to roll back the obs roof. Last year I was using Maxim and couldn’t detect a discernable difference in focus point for LRGB, so elected not to change focus. However, I now have an Ha filter so want to try some HaRGB processing and suspect that the Ha will have a different focus point, so it will be very intersted to try using this method with SGP autofocus using the offsets with auto L focussing. The focus points for all LRGB filters were different imaging with my C14, so it will be great if I can use the offsets with auto L focussing when I move back to that for galaxy season close ups in a few months time.
Cheers, Geof

Just reporting back that I successfully set up the filter offsets with my QSIwsg-5 using L for autofocus with my 4" TSAPO100Q. I took my time, maybe a couple of hours to check the offsets several times and once all was done there were only 3 steps difference between the 5 filters HaLRGB, so I’m guessing my Astronomik TypeII filters come out pretty much parfocal, at least when shooting though the 4" - I’d noticed slightly bigger focus differences shooting through the C14. I had other issues to fix last night getting PHD2 to play with the new set up, but I did shoot a single 10 minute Ha sub of IC443 (Jellyfish Nebula) and the new focus ran smoothly :slight_smile:.

I did a quick ArcSinH stretch and noise reduction on the single sub, but no calibration (Flats, darks, etc. hence hot pixels & bad columns), just to check what I’d got. Stars look good, but boy this is a faint target, as it was almost invisible without the stretch…
Many thanks for the help, I now feel ready to go capture some proper data next time we get some clear skies.
Cheers, Geof