Focuser Temperature comoensation, need help

Hi all,

this is the third thread, as we unfortunately did not get any answers to the others.

We want to use the temperature compensate option for the focuser. This works well with using just 1 Filter.

This does not work, when we use several filters, which is what we would like to do.
We want to use the option ,auto adjust focus per filter’ AND ,temperature compensate’

Today we tried to define the filter position in different ways in the filter list. We found: when give the absolute steps for all three filters (for example R:70000, G:70100, B:70200), for each filter the absolute point which has been defined in the filter list will be used. In the log file I see that the temperature compensation steps have been calculated, but the focuser does not use them. So this option failed.
We the moved the focuser to a defined position (70000) with one filter an set the filter list to 0 for this Filter (R:0). For the other filters we put in the relative Position( G:100, B:200). Here, the temperature compensation worked well for both filter where we set the relative position ( G and B) but when the filter ® which has been used to set the focus, so the one with a 0 in the filter list, then the focuser does not move at all, meaning the filter changes from B to R but the focuser does not change at all.

Can someone help how to define the filert position in such a way that both options, the ,auto adjust focus per Filter’ and the ‘temperture compensate’ option works well?
Thanks and hope for some more clarity!
Best regards,


I think I understand what you want to do – adjust filter position based on a relative adjustment to a specific filter AND on temperature change. I’m pretty sure you can’t do both - not exactly.

First off, TC movement is done before the next sub is started. For example, if the TC is 100 steps / C and sub X was focused at 1000 and the temp changed 1 degree during the exposure, then SGP will immediately move the focuser to 1100 before it starts the next sub’s focuser processing. If you are using straight auto focusing, then this movement should put the focuser close to the next focus point before any kind of AF processing starts. That’s end of TC.

If you want to focus using filter offsets, then you need multiple options checked:

  1. Use auto focus
  2. Auto adjust focus per filter
  3. Auto focus with filter [LUM]

In the Filter Setup dialog box, enter a filter position for the LUM filter; for example 70000. This is the position where the LUM filter focuses at some arbitrary temperature. Now you enter the focus positions of the RED, GREEN and BLUE filters that represent their offsets from the LUM filter at the same temperature. For example, when the LUM filter focuses at 70000, the RED focuses at 70100; the GREEN at 70200; and the BLUE at 70300.

Now SGP can auto focus with the LUM filter (at any temperature) and then SGP knows if the next sub is using the RED filter, it needs to move the focuser out 100 steps (70100 - 70000) before starting the RED sub. Similarly for the other filters. Since the auto focus focused the LUM filter first, the temperature is irrelevant.

If you feel the difference between the LUM filter focus position and the RED filter focus position is different at different temperatures, you do not have any ability to make that kind of adjustment.


Hi Charlie,
Thanks for your reply.
Unfortunately, using autofocus is not an option. We have focusboss on a feather touch.
But the auto focus does not work correctly. We tried it several times. The auto focus does not produce a V shaped curve and did not find a good focus position. We testet different move distances, but that was always the problem.
Thats why we manually focus using a bahtinov mask. We found that the temperature compensate helps holding focus pretty perfect through the whole night, but only when we use just one filter.

Is there any other idea how to solve that problem?