Enhancing focuser management


As part of the on-going feature enhancements for v3, I would like to see SGP
provide more control of the focuser to include management of the temperature
compensation option and to provide a method of implementing an initial focuser

The ASCOM standard for focusers says that if the focuser has its temperature
compenstation feature enabled, a client application may not move the focuser.
So, when I run my initial, manual focusing steps, I have to remember to go
to the ASCOM driver and disable TC. After getting my initial focus, I then
have to return to the ASCOM driver and re-enable TC. Not a big task,
assuming you remember to do it!

Since SGP’s auto focus routine expects the camera to be close to good focus
when it starts, there needs to be a way for the focuser to be automatically
moved to that initial position, with temperature compenstion taken into

So the request is to have the Focuser Control module have the following new

  1. A way to specify an initial focuser position, its corresponding
    temperature and the focuser temperature coefficent. On connect,
    the temperature compensated position is calculated and the focuser
    moved to that position. This would put the camera approximately
    in focus so that an initial auto focus run would be accurate.

  2. A check box that enables full management of the temperature compensation option.
    When checked, SGP would enable TC in the focuser on connect. If
    an auto focus routine is run manually, SGP would disable TC in the focuser,
    perform the AF run and then re-enable TC in the focuser. This would
    match what is currently being done when AF is run automatically by
    SGP during an imaging sequence.



I’d also like to repeat my request for a tolerance of a couple of microns to be permitted in the returned focused position - for the ASA focusers with an absolute encoder.


Charlie - I think that exists today. The filter look up table with its focus positions can be used like that I recall. I’m not sure about the temp.co. however as I do not go that route.



I have the same question – does the focus position recorded in the filter table include the associated temperature value? It might if you are capturing that position automatically but I suspect the temperature is not used since that focus position can be entered manually and there is no position in the array to put the corresponding temperature. For filter offset focusing, temperature is not needed – simply focus with the LUM filter and then move to the calculated offset for the selected filter.

For me, enhanced focuser management is the one thing I was hoping for in SGP v3. Right now I have to perform a manual auto focus run before target start or the initial auto focus run will fail. Is this a really big deal? No, but a nice to have feature.



I pretty sure you can set an initial position and then the startup AF routine will nail the focus. I’m assuming the temperature tracking is in steps/degree and can take it from there?



I do have a focus position entered for the LUM filter but there is not a matching temperature value. So, even if SGP moved the focuser to that position on focuser connect, which I don’t think it does, it would still be out of focus because there is not a reference temperature to use to adjust the focus position.