He takes images of many cosmological objects, including comets, planets, novae, supernovae and asteroids from his observatory in Suffolk, England.
Mobberley joined the British Astronomical Association (BAA) in 1969, aged 11, and has held various posts in the organisation since the early 1980s, culminating in his presidency from 1997 to 1999.
In 1997 the International Astronomical Union (IAU) named asteroid 7239 as "Mobberley" in recognition of his services to astronomy.
Together with the late Ken Goward, Mobberley carried out detailed research into the astronomical life and telescopes of the stage and screen comedian Will Hay, who famously discovered a white spot on Saturn in 1933.
Mobberley and Goward's research on this subject was published in the April 2009 Journal of the British Astronomical Association as a paper entitled Will Hay (1888 - 1949) and his telescopes.