I would like to understand more how the “Focus with filter” in the filter setup tab works with the ‘auto focus with filter’ on the focus settings tab and “auto adjust focus per filter”.
For instance - if I set Lum, for a narrowband filter in the ‘focus with filter’ tab (in the filter setup) with ‘auto adjust focus per filter’ set, does the AF use the Lum and then offset?
Or, put it another way - is there a setting combination that would achieve the following:
Autofocus for wideband filters (LRGB) use its LRG or B filter for focusing
Narrowband filters use Lum for AF, and then automatically offset.
There is an interplay - which I think is only partially explained in the help file and I am not entirely sure of what overrides what.
Yes, as long as “Auto Adjust Filter” is set the offsets between those two filters will be used. For Autofocus SGP will switch to your Lum filter, apply the offset difference between the two filters, then focus. After focus is complete SGP will switch back to your other filter and reverse the applied offset. So as long as the offsets are accurate you end up in focus.
Something like this is probably what you’re after.
thanks Jared - I’ll give it a go - as soon as the clouds go away. I cannot complain about the weather really, considering the appalling devastation in the wake of the hurricanes.
For sure, hard time to complain about the weather. Thankfully we’re high and dry. We got a ton of rain with Harvey (about 8-10 inches, we’re in the Austin TX area) but nothing compared to Houston.
thanks - got it. Just needed to improve some of my RGB star FWHM in a narrowband target. I have been dodging the clouds for 5 weeks and will just about accumulate 45 hours of data on a Sharpless target.
As long as we are on the subject of filter offsets and relative focus positions, I would like to make a suggestion for some future release. While I understand the current method of implementing filter offset focusing, I don’t find the current setup method intuitive since SGP is doing a lot of stuff in the background and the filter points are specified as absolute focuser positions. How about making filter offsets be just that – a position relative to some other position. I would like to always auto focus with my luminance filter and then have SGP switch to the specified filter and make a focuser movement relative to the current position. For example, my RED filter always focuses 38 steps further out than my LUM filter. I would like to setup filter offsets similar to the following:
So when auto focusing prior to taking a sub with the RED filter, the above instruction says to actually focus with the LUM filter and then move the focuser 38 steps “out”, switch to the RED filter and start the exposure. No temperature issues are involved. Using the + and - symbols makes it perfectly clear this is relative movement and not some absolute focus point.
Charlie - the same thought occurred to me - but then I realised that SGP can additionally use the points as absolutes as the starting point for an AF run. With this proposal, if you had a well behaved and fairly static system, you would need offsets and a starting point. I don’t think there is a universal solution without making yet more boxes to fill in, which at some point makes ergonomics unmanageable. I always remember the original Nebulosity ethos - the idea of making software work on a cramped, damp laptop with gloved fingers… it is always going to be a challenge as the needs become more sophisticated, which is why in another post, relating to start-up, I’m deliberately suggesting a behind-the-scenes logic change that is kinda logical (well, to my mind anyway).
I agree that you also want to be able to enter absolute focus positions. That is why I used the + and - symbols. When a + or - symbol is included in the position entry it means relative focuser position; no + or - means absolute focuser position. Also you could mix the entries. For example, the LUM filter might have an entry showing 1255. This means the LUM filter focuses at absolute position 1255. The problem is there is no way to say its 1255 @ 85 degrees and auto apply a temperature adjustment for the current conditions.
As a safe guard, SGP would not allow the + / - entry unless the “Focus with Filter” option had an entry other than “Default.”
I think the current SGPro approach has some drawbacks.
When focuser TempComp is enabled, focuser can not move so offset can not be applied.
And it also create unnecessary move of focuser, eg, when meridian flip (which requires to plate solve and move filter), it will move focuser back and forth when changing filter.
So it seems that SGPro should improve offset function as outlined by OP, which requires no focuser move outside AF routine (plate solve does not need very accurate focus)
Suggesting solutions is always tricky as it often depends on your equipment. My filters are not parfocal, far from it. My Astrodon’s colored filters are a completely different thickness to my L filter, an IDAS. With a fast scope, operating at f/4, the stars are way out of focus and I am not sure if that would work.
Using L filters for AF is also much quicker. Even so, the exposures are about 8 seconds. If that were SII, the AF routine would be very lengthy indeed.
Lastly, with an SCT, it is usually the case to AF after a meridian flip due to mirror movement. It is very difficult to find a solution that fits everyone’s setup, without making the interface overly complicated and an issue in its own right.
I would like to add my 2¢ - since the autofocus took so long with my S2 and OIII filters (90s X 9), I have run the autofocus individually on each of the filters to determine all the offsets from the Lum filter. Would love it I can run the autofocus every 30 mins on only the Lum and then focusing for the remaining filters would just use the offsets.
Graham, if I am reading your note correctly, you can do just that. You enable filter offsets and then tell the AF routine to use the Lum filter to do the focusing, You have a choice of triggers, including exposure count, time, temperature and so on.
