Documentation of the Solar Imaging System (SIS)
The data presented within the Solar Data Archive is generated by a dedicated, white-light Solar Imaging System (SIS). This documentation details the specific hardware configuration and standardized acquisition protocol employed to ensure the consistency and scientific integrity of daily solar observations of the photosphere.
1. System Development History
The current system configuration is the result of a staged evolution from a consumer-grade platform to a specialized astronomical instrument focused on high-resolution solar detail.
- Initial Configuration (Start of Archive): Data acquisition began using a standard DSLR camera coupled with a variable-focal-length 70-300mm telephoto lens on a tripod. This configuration was utilized for foundational experience and broad documentation of the photosphere and large-scale sunspot groups.
- Current Configuration (Deployment): The system was upgraded to a fixed-focal-length setup utilizing a dedicated monochrome camera and specific narrow-band filtration. This transition maximizes resolving power and signal-to-noise ratio for accurate sunspot measurement and fine structure observation. The upgrade took place during mid August until the beginning of October 2025 and therefore there’s a gap in the data archive during this time.
2. Hardware and Optical Specifications
The current SIS is optimized for high-contrast, white-light imaging, focusing on the solar photosphere. While the system utilizes components designed for stability and high performance within its specific $62.5\text{mm}$ aperture class, its scientific value is derived from the precision of the filtering and the post-processing protocol.
A. Optical Configuration
| Component | Model / Specification | Function |
|---|---|---|
| Primary Optic | Astromodified Beroflex 500mm f/8 Telephoto Lens ($62.5\text{mm}$ Aperture) | Fixed focal length. Provides stable optical performance. |
| Aperture Filter | Solar Filter Foil (Full Aperture) | Primary safety element; reduces incoming light >99.99% and blocks harmful UV/IR radiation. |
| Contrast Filter | Solar Continuum Filter (7.5nm Bandwidth) | Isolates a 7.5nm spectral band around 540nm (green light) to maximize contrast for sunspot penumbrae and granulation. |
| Safety Filter | UV/IR Cut Filter | Secondary filter placed near to the sensor plane to block residual non-visible radiation and mitigate image blurring. |
B. Digital Acquisition Platform
| Component | Model / Specification | Key Parameters |
|---|---|---|
| Camera Module | ToupTek G3M178M | Sensor: Sony IMX178M (Monochrome) |
| Sensor Resolution | $3096 \times 2080$ pixels (6.3 MP) | Pixel Size: Small pixels are ideal for sampling high-magnification solar details. |
| Data Format | SER Video Sequences | Utilized for “Lucky Imaging” protocol to overcome atmospheric turbulence. |
C. Equatorial Tracking Platform
The system requires stable, precision tracking to maintain the target within the small field of view during high-frame-rate video acquisition.
- Mount: Vixen SuperPolaris DX (SP-DX) Equatorial Mount
- Control: Motorization on Right Ascension (RA) and Declination (Dec) axes.
3. Data Acquisition and Processing Protocol
The final archived images are derived from a multi-step digital protocol designed to enhance the signal-to-noise ratio and resolve structures affected by atmospheric seeing.
3.1 Acquisition Protocol
- Targeting: The Sun is centered using the motorized equatorial mount.
- Capture Software: FireCapture software is utilized to control the G3M178M camera.
- Recording: Short-duration SER video sequences (typically 1,000 to 3,000 frames) are captured to isolate moments of excellent atmospheric stability (lucky imaging).
3.2 Post-Processing Protocol
- Frame Selection and Stacking: The SER video files are imported into AutoStakkert! (AS!3). The software analyzes the quality of each frame, aligning and stacking only the highest-quality subset (typically the best 5-10%). This process aggregates visual data to reduce noise and sharpen the image.
- Orientation and Final Adjustment: The stacked image is imported into GIMP.
- Standardization: The image is rotated to ensure a consistent orientation (Solar North Up). Minor contrast and sharpening adjustments are applied globally when necessary.
- Archiving: The resulting high-resolution image is uploaded to the Solar Data Archive with corresponding metadata.