The Sun is a G2V main-sequence star at magnitude -26.7, the only star close enough to study in detail. NEVER observe the Sun without proper solar filtration — unfiltered telescopes or binoculars will cause instant, permanent eye damage. Safe observation methods include dedicated solar filters (white light showing sunspots and faculae), H-alpha telescopes (revealing prominences, filaments, and flares on the chromosphere), and projection onto a white screen. Sunspots are dark regions of intense magnetic activity, typically 1,500K cooler than the 5,778K photosphere, and vary on the approximately 11-year solar cycle (Schwabe cycle). Solar Cycle 25 began in December 2019 and is expected to peak around 2025. During solar maximum, large sunspot groups are easily visible with proper filters, and coronal mass ejections can trigger auroral displays visible at mid-latitudes. Total solar eclipses — when the Moon's angular diameter (31.5 arcmin) precisely covers the Sun (32.0 arcmin) — are among the most dramatic natural phenomena. This geometric coincidence exists only because the Sun is both 400 times the Moon's diameter and 400 times farther away. Key missions include SOHO (1995, L1 point), the twin STEREO spacecraft (2006, stereo imaging), SDO (2010, high-resolution EUV monitoring), and Parker Solar Probe (2018, closest approach to a star, entering the corona).

The Moon reaches magnitude -12.7 at full phase and is the most detailed celestial object observable from Earth. Even small binoculars reveal hundreds of craters, the dark volcanic maria (seas), and bright ray systems from young impacts. The lunar surface is divided between dark, flat maria (iron-rich basalt, 3.1-3.9 billion years old) and bright, rugged highlands (anorthosite, 4.4 billion years). Major maria visible to the naked eye include Mare Tranquillitatis (Apollo 11 landing site), Mare Serenitatis, and Oceanus Procellarum. The best telescopic observing is along the terminator (day/night boundary), where low-angle lighting throws craters into sharp relief — features as small as 2 km are resolvable in a 200mm telescope. The Moon's 29.5-day synodic period produces the familiar cycle of phases: new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, waning crescent. Libration — a slow wobble from orbital eccentricity and tilt — reveals 59% of the surface over time rather than just 50%. Twelve Apollo astronauts walked on the surface between 1969 and 1972, returning 382 kg of samples. Recent missions include LCROSS (confirmed water ice in Cabeus crater, 2009), GRAIL (gravity mapping, 2012), Chandrayaan-3 (India's first soft landing, 2023), and SLIM (Japan, precision landing, 2024). Lunar eclipses occur 2-4 times per year and are visible from the entire night hemisphere. Total lunar eclipses produce the copper-red 'blood moon' from refracted sunlight filtering through Earth's atmosphere.