Presentation Information
[O12-P84]Sunspot Observations and a Study of Sunspot Latitudes at Tokyo Metropolitan Tachikawa Senior High School
*Koki Tsuruta1, *Rihito Nakagawa1 (1. Tokyo Metropolitan Tachikawa Senior High School)
Keywords:
sunspot,butterfly diagram,SeeStar S50
1. Introduction
Sunspots are magnetic phenomena on the solar surface that appear dark due to their relatively lower temperatures. They serve as primary indicators of the 11-year solar cycle. During the "Solar Maximum," increased sunspot activity leads to solar flares that can impact Earth’s technological infrastructure.
The Tachikawa High School Astronomy and Meteorology Club has maintained continuous sunspot observations since 1947, contributing data to the National Astronomical Observatory of Japan (NAOJ). This study compares the scale of the current Solar Cycle 25 with the previous Cycle 24 by visualizing sunspot relative numbers and latitudinal migration (Butterfly Diagrams). Furthermore, we developed a digital imaging system to minimize human error inherent in traditional sketching.
2. Data and Methodology
Observations were conducted using a Takahashi FS-152 refractor telescope. Traditionally, sunspots were recorded by projecting the solar disk onto paper. The Relative Sunspot Number (R) is calculated as:
R = k(10g + f)
Where g is the number of groups, f is the individual spot count, and k is a correction factor (1.0 for our station). We analyzed data from 1947 to September 2024, cross-referencing with NAOJ and the Royal Observatory of Belgium.
To create Butterfly Diagrams, we measured sunspot latitudes using heliographic coordinate maps. Data points were plotted as vertical lines representing the latitudinal range of spots over time. We corrected these measurements by accounting for the solar axis tilt (P) and the solar equator inclination (B).
In March 2025, we introduced the SeeStar S50 smart telescope. Images are automatically uploaded to a server via LINE and Google Drive. Using a custom image-processing program, we perform raw development, masking, and noise reduction to calculate sunspot areas, which are archived on our "TAMOS" website.
3. Results and Discussion
The Butterfly Diagram for 2005–2025 (Fig. 7) clearly visualizes the transition to Cycle 25. Both cycles followed Spörer’s Law, where spots emerge at high latitudes and migrate toward the equator. Although the "wing spread" (latitudinal distribution) fluctuates periodically, we found that the maximum spread does not always coincide with the solar maximum.
While the Relative Sunspot Number suggests that Cycle 25 is larger in scale than Cycle 24 (Fig. 8), the Butterfly Diagram does not clearly reflect this difference in intensity. This indicates that the latitudinal distribution alone is insufficient to evaluate the total magnitude of solar activity.
Additionally, the SeeStar system successfully automated data storage, but image processing occasionally failed to detect sunspots. We observed that changes in capture brightness significantly affected detection accuracy, suggesting that standardized exposure is vital for digital observation.
4. Conclusion and Future Outlook
This research highlights the limitations of using Butterfly Diagrams alone to assess cycle intensity. Moving forward, we aim to extend our diagrams to data before 2005 (Cycle 23 and earlier) to establish more robust patterns. We will also refine the digital imaging system by optimizing brightness settings to evaluate solar activity through total sunspot area, bridging our historical archives with modern technology.
Sunspots are magnetic phenomena on the solar surface that appear dark due to their relatively lower temperatures. They serve as primary indicators of the 11-year solar cycle. During the "Solar Maximum," increased sunspot activity leads to solar flares that can impact Earth’s technological infrastructure.
The Tachikawa High School Astronomy and Meteorology Club has maintained continuous sunspot observations since 1947, contributing data to the National Astronomical Observatory of Japan (NAOJ). This study compares the scale of the current Solar Cycle 25 with the previous Cycle 24 by visualizing sunspot relative numbers and latitudinal migration (Butterfly Diagrams). Furthermore, we developed a digital imaging system to minimize human error inherent in traditional sketching.
2. Data and Methodology
Observations were conducted using a Takahashi FS-152 refractor telescope. Traditionally, sunspots were recorded by projecting the solar disk onto paper. The Relative Sunspot Number (R) is calculated as:
R = k(10g + f)
Where g is the number of groups, f is the individual spot count, and k is a correction factor (1.0 for our station). We analyzed data from 1947 to September 2024, cross-referencing with NAOJ and the Royal Observatory of Belgium.
To create Butterfly Diagrams, we measured sunspot latitudes using heliographic coordinate maps. Data points were plotted as vertical lines representing the latitudinal range of spots over time. We corrected these measurements by accounting for the solar axis tilt (P) and the solar equator inclination (B).
In March 2025, we introduced the SeeStar S50 smart telescope. Images are automatically uploaded to a server via LINE and Google Drive. Using a custom image-processing program, we perform raw development, masking, and noise reduction to calculate sunspot areas, which are archived on our "TAMOS" website.
3. Results and Discussion
The Butterfly Diagram for 2005–2025 (Fig. 7) clearly visualizes the transition to Cycle 25. Both cycles followed Spörer’s Law, where spots emerge at high latitudes and migrate toward the equator. Although the "wing spread" (latitudinal distribution) fluctuates periodically, we found that the maximum spread does not always coincide with the solar maximum.
While the Relative Sunspot Number suggests that Cycle 25 is larger in scale than Cycle 24 (Fig. 8), the Butterfly Diagram does not clearly reflect this difference in intensity. This indicates that the latitudinal distribution alone is insufficient to evaluate the total magnitude of solar activity.
Additionally, the SeeStar system successfully automated data storage, but image processing occasionally failed to detect sunspots. We observed that changes in capture brightness significantly affected detection accuracy, suggesting that standardized exposure is vital for digital observation.
4. Conclusion and Future Outlook
This research highlights the limitations of using Butterfly Diagrams alone to assess cycle intensity. Moving forward, we aim to extend our diagrams to data before 2005 (Cycle 23 and earlier) to establish more robust patterns. We will also refine the digital imaging system by optimizing brightness settings to evaluate solar activity through total sunspot area, bridging our historical archives with modern technology.