Auto focus settings

[admin]

Hi Chris,

sorry about the confusion - can you confirm which button you used to launch the scan in the focus assistant please?

thanks,

Robin

[Chris_h]

Apologies for the late reply, busy weekend.

Tools - Focus Assistant

I tried using Contrast Detection, Multi Star FWHM and FWHM. It used 10 and 200 in all of them, even thought the settings were set to 1 and 1.

I did get autofocus to work with Deep Sky Sequence Planner though! My settings worked like a charm there!

[admin]

Hi Chris,

right, but in the focus assistant, are you using the Scan In / Scan Out buttons or the Refocus button?

I would expect the scan in/scan out buttons to use the settings that you have adjusted in the options pop up.

The refocus button however uses the settings as they were on the last successful scan (that found best focus) as these are the settings that SharpCap *knows* worked at least once. If you want the refocus button to use different settings, set them up in the popup, use scan in/scan out and then 'Goto best focus position', which will reset the settings used by 'Refocus'.

Hope that makes sense at least a bit

cheers,

Robin

[Chris_h]

Right, I just used Refocus. That would explain it I guess

Thanks!

- Chris

[abillionnewstars]

I am going to start doing EAA for public outreach. I was planning to use auto focus to get the best focus possible BUT SC process seems to be quite confusing in that regard. Is there somewhere a guide to follow? I use NINA for my regular imaging and autofocus without a glitch.

Thanks

[woldsweather]

How3 do you get SXC to plot the graph?

[kaymann]

I have needlessly struggled with SC Auto Focus for a long time and then Borodog hinted, well more than hinted, there are two things (I add one more) you can do to make it so much easier for yourself:

Set up exposure for speed of the AF run, and gain for the number of stars selected in Multi-Star Auto Focus to be a high enough count to start.

Backlash -

• Do not try to tirelessly try to figure out the exact amount of backlash your focuser has.

• Instead get a close approximation or simply estimate of the worst case scenario for your brand of focuser.

• For my ZWO EAF all indicators from other owners are it is going to be around 100 or so.

• Now go into File-SharpCap Settings-Hardware-Focuser. Set the radio button to Overshoot, approach in the (I choose positive) direction. The reason I choose positive is because of bullet list below.

• I then set the overshoot to well over my estimated backlash. So in my ZWO EAF case I set my overshoot to 200.

• This is effectively the same as putting in the exact amount and having SC overshoot by that exact amount. The amount of time saved in putting the exact backlash in is minimal as the time difference from going from 100 overshoot to 200 overshoot. The idea is to make sure you go far enough in overshoot to absorb the backlash.

Be out of focus Negative when starting autofocus and then start the SC autofocus routine with the Positive button.

• I try to get close to focus then I hit the Negative button so it takes me back at least 200 steps. Even when I back it up 500 steps things work perfectly.

• Doing this negative starting point by pushing the focuser negatively, and then starting AF with the Positive button ensures that backlash has been consumed before the AF procedure even begins.

• Then SC will continue in the positive direction where there is no need to worry about backlash.

Since starting this new procedure it has resulted in successful auto focus runs every single time. Before doing these three procedures my auto focus would typically run forever and completely fail into nowhere near focus results.

[woldsweather]

Thanks for that, imaging now but will try this next time.

[admin]

Hi @kaymann,

out of interest, what things were you doing differently before that might be associated with the problems you were seeing? I might be able to tweak the user interface to make it less likely that people try to do it the bad way and more likely to do it the good way.

thanks,

Robin

[kaymann]

Robin, there were a couple of things I was doing wrong, which all stemmed from the fact that I had no idea what the science behind the curve was doing (how could that curve find perfect focus without actually going there at least once) if the curve is not understood clearly then assumptions made will invariably lead you down the rabbit hole of failure. Common misunderstanding: SC tries here nope, tries there nope, tries further nope, SC this one I tried is closest I'll leave it there. That's not what is happening SC is extrapolating to the best focus - this has to be super clear...

Here are some Ideas that might take make it easier.

• Start negatively defocused (for the sake of SCT Mirror Shift) no options less confusing.

• Defocus before starting is a hard step to grasp (big popup maybe)

• Instruct to always defocus negatively and with the above bullet, half the battle is won

• When I was worried about exact back focus I actually got it wrong and if I get it wrong by not being enough well everything broke down.

• Some how make overshoot and come in from the same side on every focus more of the default instead of using specific backlash