astronomy

William Lassell

William Lassell is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand William Lassell rather than just read about it. In short: William Lassell (18 June 1799 – 5 October 1880) was an English merchant and astronomer. He is remembered for his improvements to the reflecting telescope and his ensuing discoveries of four planetary satellites.

Key takeaways

William Lassell belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect William Lassell to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of William Lassell from memory before moving on to harder problems.

Reference excerpt

William Lassell (18 June 1799 – 5 October 1880) was an English merchant and astronomer. He is remembered for his improvements to the reflecting telescope and his ensuing discoveries of four planetary satellites.

Life William Lassell was born in Bolton, Lancashire, on 18 June 1799. He received his early education in Bolton and later attended Rochdale Academy. After the death of his father, William Lassell was apprenticed to a merchant in Liverpool from 1814 to 1821. He later made his fortune as a beer brewer, which afforded him the means to pursue his passion for astronomy. He built an observatory at his house "Starfield" in West Derby, a suburb of Liverpool. There he had a 24-inch (610 mm) aperture metal mirror reflector telescope (a.k.a. the "two-foot" telescope), for which he pioneered the use of an equatorial mount for easy tracking of objects as the Earth rotates. He ground and polished the mirror himself, using equipment he constructed. The observatory was later (1854) moved further out of Liverpool, to Bradstones. In 1846, Lassell discovered Triton, the largest moon of Neptune, just 17 days after the discovery of Neptune itself by German astronomer Johann Gottfried Galle, using his self-built instrument. In 1848, he independently co-discovered Hyperion, a moon of Saturn. In 1851 he discovered Ariel and Umbriel, two moons of Uranus. In 1855, he built a 48-inch (1,200 mm) telescope, which he installed in Malta because of the observing conditions that were better than in often-overcast England. While in Malta his astronomical observing assistant was Albert Marth. On his return to the UK after several years in Malta, he moved to Maidenhead and operated his 24-inch (610 mm) telescope in an observatory there. The 48-inch telescope was dismantled and was eventually scrapped. The 24-inch telescope was later moved to Royal Observatory, Greenwich in the 1880s, but eventually dismantled. Lassell was a Fellow of the Royal Astronomical Society (FRAS) from 1839, won the Gold Medal of the Royal Astronomical Society in 1849, and served as its president for two years starting in 1870. He was elected a Fellow of the Royal Society (FRS) in 1849 and won their Royal Medal in 1858. Lassell was also a Fellow of the Royal Society of Literature (FRSL). He was furthermore elected an honorary Fellow of the Royal Society of Edinburgh (HonFRSE) and of the Society of Sciences of Upsala, and received an honorary LL.D. degree from the University of Cambridge in 1874. Lassell died in Maidenhead in 1880 and is buried at St. Luke's Church. Upon his death, he left a fortune of £80,000 (roughly equivalent to £8,300,000 in 2025). His telescope was presented to the Royal Observatory in Greenwich. The crater Lassell on the Moon, a crater on Mars, the asteroid 2636 Lassell and a ring of Neptune are named in his honour. At the University of Liverpool the William Lassell prize is awarded to the student with the highest grades graduating the B.Sc. program in Physics with Astronomy each year. In Alfred Bester's novel The Stars My Destination, an inhabited moon of Neptune is named Lassell.

Obituaries Astronomical Register, 18 (1880), p. 284 Nature, 22 (1880), p. 565 The Observatory, 3 (1880), p. 587 Monthly Notices of the Royal Astronomical Society, 41 (1880), p. 188

See also List of largest optical telescopes in the 19th century

References

External links

Biography and other topics Archived 2 August 2020 at the Wayback Machine Short biography and pictures Biography and technical detail of telescopes Archived 11 May 2023 at the Wayback Machine

Worked examples

Example 1 — a first encounter with William Lassell

Start with the simplest possible case. Write down what William Lassell claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to William Lassell before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about William Lassell ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of William Lassell

In research: William Lassell appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses William Lassell in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: William Lassell is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1799 births, 1880 deaths, 19th-century British merchants, so understanding it makes those chapters shorter.
In everyday life: Look for William Lassell outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study William Lassell in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what William Lassell means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain William Lassell out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is William Lassell in simple terms?

Why does William Lassell matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study William Lassell?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on William Lassell.