Astronomy Plus eADC-V3 Electronic Atmospheric Dispersion Corrector

The SunObserver eADC V3 is the third-generation electric atmospheric dispersion corrector (ADC) equipped with Zero Image Shift technology, designed for advanced astrophotography and high-precision visual observation. This updated V3 version includes enhanced automation, improved optical correction logic, expanded software compatibility, and a completely redesigned encoder control interface.

At the core of the eADC V3 is a system of four prisms in two groups, manufactured from high-quality optical glass and coated with broadband AR (anti-reflection) coatings. The integrated accelerometer sensor detects the current orientation of the telescope and automatically calculates the required atmospheric dispersion correction, including during meridian flips, without any manual adjustment.

Key Features

• Automatic dispersion correction based on the real-time altitude of the observed target

• Zero image shift ensures perfect image centering during adjustments

• Dual operation: offline via rotary encoder or online via PC software (Windows only)

• Compatible with Newtonians, refractors, catadioptrics, and Cassegrain optical systems

• Integrated tilt compensation for lateral chromatic aberration correction

• Supports automatic orientation detection even during zenith flips

What’s new in eADC V3

• Improved accelerometer logic for fully automatic real-time dispersion compensation

• Refined rotary encoder interface for precise offline control

• Full support for latest ADC alignment tools in Sharpcap 4.0+ and ASICAP

• Optimized performance for fast optical systems using focal extenders

• Updated firmware logic for zero image shift and automatic mode detection

• Refined tolerance for tilt correction across wider altitudes

Operating Modes

• Mode 0: for refractors, catadioptrics, and Cassegrain systems without a diagonal mirror or erecting prisms between telescope and eADC

• Mode 1: for Newtonian telescopes, which use a 90° secondary mirror; requires proper physical orientation (long side of eADC parallel to optical axis)

Encoder-Based Standalone Operation

eADC V3 features a digital display and rotary encoder for fully autonomous control:

• Clockwise rotation: increases selected parameter

• Counterclockwise rotation: decreases selected parameter

• Single press: cycles through compensation coefficient, mode selection, and tilt adjustment

• All settings are saved automatically after 4 seconds of inactivity

Dispersion Compensation Process

1. Initialization: After powering up (USB or power bank), the device boots up (“Initializing” → “smart eADC” in ~60 seconds)

2. Adjustment:

   • Point the camera at the target

   • Increase exposure/saturation or decrease green gain for better chromatic visibility

   • Use Sharpcap 4.0+ or ASICAP ADC Alignment tools for precision tuning

   • Adjust the dispersion coefficient until red/blue fringes disappear

   • If chromatic tilt remains, adjust horizontal tilt compensation

3. Visual use: Follow the same principle as for imaging; tilt compensation may be necessary

Installation & Optical Considerations

• f/10 and slower telescopes: negligible image degradation

• Fast telescopes (f/7, f/5, f/4): use of a focal extender is strongly recommended to reduce aberrations

• Keep camera sensor at a moderate distance from the prism to avoid performance loss and dust reflection

• Clean prism surfaces regularly to ensure optimal optical clarity

Operating Altitude Limits

• Minimum target altitude: ~10° — below which the eADC V3 may not offer sufficient compensation

• Maximum recommended target altitude: ~82° — above which the eADC may introduce chromatic aberration

• Above 82°: it is advisable to remove the eADC from the optical train

PC Software (Windows only)

The eADC V3 includes a Windows-compatible software suite for advanced users:

• Communication via FTDI FT232RQ virtual COM port

• Automatic detection and COM port assignment

• Real-time readout of temperature, target elevation, compensation, and tilt

• Adjustable parameters via mouse sliders or keyboard arrows

• Auto-refresh every 4 seconds (optional)

• Safe switching between Mode 0 and Mode 1 with auto-restart after 4 seconds