Ability to make filter offsets relative to another filter


Currently filter offsets are absolute which is fine if the camera is fixed to the focuser permanently and there is no manual focus done. For those of us that have Moonlite or Feathertouch focusers and also those who may remove/refit their camera periodically (push-fit fitting) to perhaps change or clean filters or even refocus then inevitably the position changes. With the change in position will be a change in offset values so these would need to be reset per filter. If the filter section supported relative offsets then only one filter need have its focus position re-recorded rather than 5 or 7 etc. Obviously all the relative offsets would be against one filter.

This feature could save a lot of time refocusing.

Many thanks


This is not accurate. They are entered in an absolute way, but we only consider the difference between positions when making a correction from one filter to another.

Please see instructions here: http://mainsequencesoftware.com/Content/SGPHelp/AutoAdjustFocusPerFilter.html


Thanks for pointing out my error. Internally they are treated as relative but externally they don’t seem to be. For instance, if I disengaged the motor and focused manually then the absolute position would be lost. The mechanical position and offsets would still be valid but the focus positions for each of the filters would need to be re-acquired (quite a lengthy process for some cameras).

What I’m saying is that since the offsets are still valid then I really only need the focus position for one filter. Could you consider exposing the offsets for example:

  1. Allow a filter to be marked as the master (use recorded absolute position as is currently the case).
  2. Allow the offset values to be keyed in as an alternative to the absolute position (affecting all or none) making filters slaves.

Apologies for not explaining it better the first time and I hope this makes sense !

Many thanks


Apologies, my ignorance, still learning this SW. I see this is already accounted for in a more elegant way - I should read more !


Hello Jared and Ken,
first, thank you for your previous reply,
I would just add a thing concerning the filter focus offset. I realized this night that the focus offset did not work because I have not clicked on the 'set focus for …" button. I have well imported the offset values from the filter wheel driver and I thought that this was sufficient, but not … ok I have not read this precise part of the SGP instruction, as this functionality appears to be evident, in addition if you re-install every night your telescope you do not want a ‘rigid’ absolute mode and you believe that the instruction ‘successfully’ imported from the FW driver will work.
May be it would be a good think to just made a warning to inform the lazy users, like me,
that SGP works with an ‘hybrid’ filter focus offset mode, that the offset entered in the fw driver are not used as such and that the user have to choose an absolute starting focus position to make SGP working correctly.
Thank you.