Tutorial Seven: Alignment Subsystem

This tutorial demonstrates how to create a telescope simulator that uses the INDI Alignment Subsystem to improve pointing performance. The Alignment Subsystem helps correct for mechanical and optical misalignments in telescope mounts.

What You’ll Learn

  • How to integrate the INDI Alignment Subsystem into a telescope driver
  • How to handle alignment points and sync operations
  • How to transform coordinates using the alignment model
  • How to improve telescope pointing accuracy

Source Code

The source code for this tutorial can be found in the INDI library repository under the examples/tutorial_seven directory.

INDI Alignment Subsystem

The INDI Alignment Subsystem provides a framework for improving telescope pointing accuracy by building a mathematical model of the telescope’s pointing errors. The key components are:

  1. Alignment Database: Stores alignment points (pairs of requested and actual coordinates)
  2. Math Plugins: Implement different mathematical models for coordinate transformation
  3. Coordinate Conversion: Transforms between different coordinate systems (e.g., equatorial to horizontal)

Code Explanation

This tutorial demonstrates:

  1. Alignment Integration:

    • Initializing the Alignment Subsystem
    • Adding alignment-related properties to the driver
    • Handling alignment commands

  2. Coordinate Transformation:

    • Converting between coordinate systems
    • Applying the alignment model to correct coordinates
    • Handling sync operations to build the alignment model

  3. Telescope Control:

    • Implementing GOTO operations with alignment correction
    • Simulating telescope movement
    • Reporting telescope status

Running the Tutorial

To run this tutorial:

  1. Build the tutorial using CMake:

    cd /path/to/indi/build
make

  2. Run the INDI server with the tutorial driver:

    indiserver -v ./tutorial_seven

  3. Connect to the server using an INDI client that supports the Alignment Subsystem (like KStars/EKOS).

  4. You can now perform alignment operations:

    • Slew to a known object
    • Sync the telescope to the object’s actual position
    • Repeat for multiple objects to build an alignment model
    • Observe improved pointing accuracy in subsequent slews

Next Steps

This tutorial demonstrates how to use the INDI Alignment Subsystem to improve telescope pointing accuracy. In Tutorial Eight, we’ll learn how to create a simple rotator device.