Who is the 17th century scientist that pioneered telescopic observations of the sun?

Galileo Galilei (1564-1642) was the first to use a telescope for systematic astronomical observations of the Sun in the early 17th century (around 1610-1613). He observed and recorded sunspots, challenging the then-prevailing belief in celestial perfection. Isaac Newton came later (17th century). Nicolaus Copernicus (16th century) developed the heliocentric model but died before telescopes were invented. Louis Pasteur was a 19th-century microbiologist.