Auto Focusing Aid

The Auto Focusing Aid is accessible from Tools tab
The automated focusing requires some initial preparation and measurements in order to provide best results. Please read this section before you start using it.
Hardware requirements
Use the button Settings to open the dialog box and tune the options related to auto-focusing.
The settings Threshold, Coarse/Fine Step (see the explanations below) and the backlash compensation are the things that affect the quality and success of the auto focus. Usually these parameters are set one time only.
Here are two scenarios how to use the automated focusing:
Auto-Focusing with Images
Auto-Focusing with LiveView (supported for DSLRs)
The Auto-Focusing Aid is designed to collect data that at later stage can be used to calculate the temperature compensation. When “Record results” is enabled APT will store data for every successful focusing. If you want to make deep study of the focus change during the night you can leave APT to make continuous re-focusing by enabling “Loop focusing”.
The collected data will be analyzed in the Analyzer which is expected to be ready in one of the next versions. Meanwhile you can use the Analyzer button to export the data in a file that to be opened with MS Excel or similar application.
Tips&Tricks. Closer to the focus point you start Auto-Focusing faster APT will finish.
Auto Focusing Aid

Ringy Thingy

1. Ringy Thingy
Ringy Thingy is an innovative way to edit numeric values using only mouse or touch pad. See details and animation how to use it in the Application Interface notes.


2. Threshold
This is the focus value tolerance. Usually because of the atmosphere turbulence the FWHM (Full Width Half Maximum) / HFD (Half Flux Diameter) readings are changing even when there is no focuser move. Threshold is here to ignore these changes. It is important to measure it well. If it is too big the focusing will be inaccurate, if it is too small the Auto-Focus Aid will take the turbulence for focus change and will make wrong moves. So make the focus manually using Focus Aid on a star, then:
  • If you use EOS LiveView increase the stack count to get more stable readings of FWHM / HFD. Leave it for few seconds and mark what is the scale of the changes. Enter for Threshold a bit bigger value than the observed one. For example if you see that FWHM is changing in the range 3.78 - 3.76 set the Threshold to 0.03 or 0.04.
  • If you use focusing with images, it is better to use exposures with duration enough to eliminate the turbulence usually 2-5s is enough. However we suggest to execute an "Focusing/Framing" type plan to determine the threshold value.  As for LiveView see the scale of FWHM / HFD changes and set a bit bigger value.
Note: The Threshold can be different for FWHM and HFD, so inspect the readings changes for the metrics that you will use for auto-focusing!

Fine Step

3. Fine Step
This is the step for the fine focusing. Defines how many steps are needed to make in order to see change in FWHM/HFD (change that is bigger than the Threshold). It depends on how the motor is installed, the f-ratio of the scope, how fine the steps are and so on. The idea is that there is no need to make 5 moves if the FWHM/HFD will not change at all for less than 5 focuser steps. So in this case the Fine Step has to be 5 and APT will make 5 stapes every time when there is need to change the focuser position.

Coarse Step

4. Coarse Step
APT makes the focusing into two passes. The first one is to find the range where is the focus point using bigger steps and then find the exact point using fine steps. Use the controller or APT to move to focuser and find how many steps make a noticeable change in the FWHM/HFD readings. The change should bigger than Threshold*2. Don't set too very big step because the second pass will be very long. Also don't set too small value because APT can miss the FWHM/HFD change.

Max moves

5. Max moves
Defines the upper limit of the focuser moves that to make in trying to find the focus. When reached the aid will report and error and stop.

Pause after move

6. Pause after move
Defines how many second to wait after focuser move is finished before taking another image. The default value is 1.
  • 7

    Focusing source

7. Focusing source
Defines what to use for focusing - Images or LiveView (LiveView is supported only for DSLRs).

Focusing Method

8. Focusing Method
Defines which metrics to use for Auto-Focusing - FWHM (Full Width Half Maximum) or HFD (Half Flux Diameter).
This setting is also used by the EOS Lens auto-focusing.


9. Loop
When enabled the Auto-focusing will make continuing focusing till it is manually stopped. Use this option if you want to collect data and study how the focus changes with the temperature changes.


10. Record
When enabled will store information for every successful focusing. Useful when calculating a temperature compensation value.

Run / Stop

11. Run / Stop
Starts/Stops the auto-focusing.


12. Status
Shows the current status of Auto-Focusing Aid.


13. Settings
Opens the settings dialog box.


14. Analyzer
In one of the next versions it will open a dialog box for analysis of the stored focusing data and temperature compensation calculation. Meanwhile you can use it to export the data in a file that to be opened with MS Excel or similar application