This section gives ASCOM and INDIGO / INDI compatible focusers control. APT can control two focusers in same time - one for the main imaging scope and second for the guider like motorized Off-Axis-Guiders (OAG). The Auto Focusing features can be used with the first focuser, while the second focuser control could be used to apply different position offset per filter (this is unique feature, by the time when APT 4.20 is released, no other imaging software had it before!)
There are two types of focusers Absolute and Relative. The Absolute use servo motor to drive the telescope focuser and can measure every move in steps and to give the exact position of the focuser in every moment. The Relative use DC motor and can't measure the exact position. APT can make emulation and make Relative focuser to look like Absolute. To enable the emulation use the options in Scope & Focuser settings tab.
APT is capable to apply temperature focus compensations and focuser backlash compensations. For details on configuring them see Scope & Focuser settings tab. Note that temperature compensations will not be applied when Focusing Aid, Auto Focus Aid or Bahtinov Aid are open.
Some focusers has built-in temperature sensor. Also there are some DIY (Do-It-Yourself) projects based in the Arduino platform that has both temperature and humidity sensors. For more information on how such sensors can be used see the section Temperature /Humidity Sensors.
If you have Meade focuser connected to the AutoStar hand-controller see Meade Specific section.
The focuser connection is used or can be used by the following APT features:

Active Focuser Selection

1. Active Focuser Selection
Defines which focuser is active in the moment. The control options bellow are applied to the active focuser.

Connect / Disconnect

2.  Connect / Disconnect
When you connect a focuser for the first time you will be asked to select the connection parameters from ASCOM or INDIGO / INDI selector dialog. APT will remember your selection and when you click again on the “Connect” button it will use the previous settings automatically. If you want to change the connection parameters, use “Shift+Click” on the Connect button. Use Ctrl+Click to forget the selected connection parameters.


3.  Position
If the focuser is of type Absolute shows the current position of the focuser. If the focuser is Relative the position is not available, unless emulation is enabled in Scope & Focuser settings tab.

Position Bookmarks

4. Position Bookmarks
Allows storing and using of three focuser position values.
To store the current focuser position use Shift+Click. To use stored position, just click on the button and the value will be populated into the GoTo field.
Ctrl+Click on the bookmark buttons stores the values in GoTo edit box as bookmark.


5.  Settings
Opens the settings dialog of the ASCOM driver. If this action is not supported by the driver, use Shift+Click on Connect button and then click Properties in the driver selector dialog box.

GoTo section

6. GoTo section
This section allows to move the focuser to particular position. Enter the position (or use the Position Bookmarks) and click on GoTo button. This requires Absolute focuser or enabled positions emulation (Scope & Focuser settings tab).
If position emulation is enabled Shift+Click on the Goto button will set the entered GoTo value as current position of the focuser.

Step Size

7. Step Size
Defines how many positions to change on every move step. The button "..." allows creation/selection of different step size profiles. When Step size control is focused you can use arrow up/down keys to scroll through the profiles you have defined.

Out x5

8. Out x5
Move the focuser in outward direction with five times the defined step size.


9. Out
Move the focuser in outward direction with the defined step size.


10. Stop
Stops the running focuser move.


11.  In
Move the focuser in inward direction with the defined step size.

In x5

12.  In x5
Move the focuser in inward direction with five times the defined step size.