Astronomer Dr David Whitehouse told Sky News that Sir Patrick Moore had "loved astronomy more than he loved himself".
He was passionate, he was dedicated and had an unselfish love of astronomy and he passed that on to everybody who knew him and he came across. He was a difficult person personally to deal with on many occasions, he was sometimes awkward, truculent, stubborn but that was Patrick, that was part of his remarkable personality which so many people came to enjoy and love.
– Dr David Whitehouse
I think many people realised he was a unique person.
He was not a professionally trained astronomer and yet did professional quality work, particularly when it came to mapping the Moon in the 1950s - I think every astronomer in the world owes something to Patrick Moore.
Fellow broadcasters have been sharing their tributes to Sir Patrick Moore on Twitter:
Very sad news about Sir Patrick. Helped inspire my love of astronomy. I will miss him!
A man I've admired from childhood. Sir Patrick Moore has died - great character .... Finally he's going up amongst the Heavens. #RIP
RIP Patrick Moore - you taught me to look up x
The last Sky At Night programme was broadcast on Monday.
Sir Patrick has only missed one episode since it began, on 24th April 1957, when he was struck down by food poisoning.
His trademark monocle, unique delivery and occasional performances on the xylophone made him a familiar target for satirists and impressionists, but his scientific credentials were never in doubt.
The show's guests have included many prominent scientists as well as Goon Show star Michael Bentine and astronauts Neil Armstrong and Buzz Aldrin.
But the demands of live television have led to the occasional blooper, with Sir Patrick famously once swallowing a fly live on air.
Actor and singer John Barrowman has tweeted his sorrow at the death of Sir Patrick Moore:
The stars will not shine as bright tonight. RIP Sir Patrick Moore. Jb
Queen guitarist Brian May paid tribute to Sir Patrick Moore, calling him a "dear friend and a kind of father figure to me".
He said: "Patrick will be mourned by the many to whom he was a caring uncle, and by all who loved the delightful wit and clarity of his writings, or enjoyed his fearlessly eccentric persona in public life.
"Patrick is irreplaceable. There will never be another Patrick Moore. But we were lucky enough to get one."
– A statement from a group of Sir Patrick Moore's friends and staff
Over the past few years, Patrick, an inspiration to generations of astronomers, fought his way back from many serious spells of illness and continued to work and write at a great rate, but this time his body was too weak to overcome the infection which set in, a few weeks ago.
He was able to perform on his world record-holding TV Programme The Sky at Night right up until the most recent episode.
His executors and close friends plan to fulfil his wishes for a quiet ceremony of interment, but a farewell event is planned for what would have been Patrick's 90th birthday in March 2013.
Astronomer Sir Patrick Moore died today aged 89, a group of his friends and staff said.
The broadcaster "passed away peacefully at 12.25pm this afternoon", at his home in Selsey, West Sussex, they said in a statement:
"After a short spell in hospital last week, it was determined that no further treatment would benefit him, and it was his wish to spend his last days in his own home, Farthings, where he today passed on, in the company of close friends and carers and his cat Ptolemy."