EKOS has been making some tremendous progress over the last year. The addition of the new polar alignment feature without needing Polaris puts it again ahead of the competition. Not that EKOS needs to be in competition with anyone. But it's always been my favorite imaging application due to all of the advanced features.
But looking forward I'd like to put focus on some additional features that would be super beneficial.
First would be a repeatable way to measure focuser backlash. Nina used to do this, but they've taken it out. Now they rely on a focuser run that moves the focuser out of focus in one direction, then slowly moves backwards in small increments taking focus measurements of the FWHM. At the point that the FWHM measurement starts to drop, you take the total steps from the first point to the first drop, and that's your focuser backlash. It seems this type of measurement could be done automatically by the system if implemented.
Second would be focuser characterization. This would be an attempt to measure focus changes from on focus, to out of focus, to determine the best step size increment, max step, etc. Nina also has a manual method to determine this, and it worked quite well for their focus system.
- Example: assuming a starting point of good focus of 4000 steps, we will move the focuser outward by an amount of 10 steps at the time, and take a new exposure at the end of each increment to check the measured HFR. Let's say that after 12 moves (120 focuser steps) no or just a couple of very defocused stars will still be detected by N.I.N.A. The value of 120 steps will therefore represent be the max increment. Scaling it by 80% (roughly 100) and dividing it by the Initial Offset (4) will give us an <em>Auto Focus Step Size</em> of 25.
I think a lot of the focus issues that have lingered over the last few years have come down to these two things primarily. And not the focus system itself. So any help to make focusing reproducible, and reliable will go a long way to making this a better system.
Third is temperature focus compensation. This is measuring the focus change over time (could be measured with a log noting the temperature and focus change), then deriving the rate of change in steps per degC drop in temperature. This requires the first two focuser tools are implemented. And if this is then implemented, will eliminate multiple additional focus runs throughout a night, giving you more imaging time. Focus will be adjusting in real time along with the drop in temperature as characterized for your system using the noted method. You would want to save the rate of change per telescope/focus system attached so that you could get repeatable results with different imaging rigs. What I regularly experience with the traditional method of focus, is my first frames are very good, then begin to become poor until a new focus routine is invoked by either FWHM change, forced time, filter change, or set temp change. I'd like something that is more consistent throughout the night, and only require a forced focuser run if focus exceeds some predetermined FWHM change.
Thoughts?