Night Sky & Meteor Detection
Sky brightness, light pollution, and detecting meteors with a camera
Nepal sits at the edge of some of the world's last truly dark skies — high-altitude sites in the Himalaya see the Milky Way with the naked eye. Yet even here, light pollution is creeping in. In this activity students use the station's sky camera and brightness sensor to quantify sky darkness, observe or reconstruct meteor events, and connect sky quality to both scientific access and cultural heritage.
विधि
- Measure sky brightness: observe the brightness value shown by the station (0–255 scale). Record it now, then compare to a night reading if available in the image history.
- Light pollution mapping: look at the live image. Which directions show the brightest horizon glow? What human settlements or infrastructure lie in those directions?
- Estimate cloud cover: use the station's cloud cover % and compare to your own visual estimate. How would cloud cover affect a night sky observation?
- Meteor detection method: explain in your own words how frame-differencing works — comparing two consecutive images and highlighting pixels that changed. Why would this flag meteors?
- Classify a streak: if any linear streak appears in the sky image, estimate its angular length, direction, and whether it could be a meteor, aircraft, or satellite. Give reasons.
- Bortle scale: use the station's night brightness reading to estimate the Bortle class of this site (1=darkest, 9=city). What would need to change to improve it by one class?
छलफल प्रश्नहरू
- The sky camera brightness reads 8 at midnight. What does this tell you about cloud cover vs. light pollution? What extra measurements would help distinguish the two causes?
- Meteor detection requires capturing fast streaks on slow hardware. The OV5647 runs at ~15 fps at full resolution. What frame rate and exposure would you need to reliably capture a meteor moving at 70 km/s across 10° of sky?
- Light pollution is rarely discussed as an environmental problem in Nepal. Who does it harm? Who benefits from the lights that cause it? Is it worth regulating?
कार्यपत्र
1. A meteor enters the atmosphere at 40 km/s and produces a visible streak for 0.3 seconds. Calculate the length of the streak in km, assuming it travels at an altitude of 100 km. [3 अंक]
उत्तर मार्गदर्शन (शिक्षकका लागि)
Distance = speed × time = 40,000 m/s × 0.3 s = 12,000 m = 12 km. Accept 10–15 km range with working shown.
2. Explain the frame-differencing technique for meteor detection. Why would aircraft and satellites also be flagged, and how could you distinguish them from meteors? [5 अंक]
उत्तर मार्गदर्शन (शिक्षकका लागि)
Frame differencing: subtract consecutive frames; changed pixels mark a moving object. Aircraft: dashed/intermittent streak (flashing nav lights ~1 Hz); satellite: slow consistent arc, visible only in twilight; meteor: continuous bright streak, duration <1 s, no colour change. Award marks for explaining differencing and identifying specific distinguishing features.
शब्दावली
- Bortle Scale
- A nine-level scale measuring night sky darkness. Class 1 is the darkest; class 9 is the most light-polluted inner-city sky.
- Frame Differencing
- A computer vision technique detecting motion by comparing two consecutive frames and highlighting pixels that changed.
- Meteor Shower Radiant
- The point in the sky from which a shower's meteors appear to originate — caused by Earth entering a stream of cometary debris.
- Sky Brightness
- How bright the night sky appears, combining natural sources (stars, airglow) and artificial light pollution.
- Light Pollution
- Excessive artificial light brightening the night sky, wasting energy and harming astronomy, ecosystems, and human sleep.
विस्तार
Write a Python script that loads two consecutive camera images and computes the absolute difference image using Pillow. Apply a threshold to suppress noise and count "bright streak" pixels. Test it on any two images from the station archive.