More than 100 people are expected to attend the conference, which has not been held in Dunedin since 1975.
Organisers said hosting the event was an honour for the Dunedin Astronomical Society, the country's oldest astronomical society which will celebrate its centenary this year.
The three-day gathering will be held at the Otago Museum, starting on May 28.
Dr Ryder (42) grew up in Dunedin and attended Kings High School, where he was dux in 1984.
A former member of the Dunedin society, during the conference he will give a public talk on supernovas at the museum's Hutton Theatre on May 30, starting at 3.30pm.
Dr Ryder began his tertiary studies at the University of Otago before switching to Canterbury University because it offered an astronomy specialty.
He gained a BSc (Hons) degree in astronomy in 1988.
He gained a PhD in astronomy at the Australian National University, Canberra, in 1993.
Mr Ryder now heads the Australian Gemini Office, which co-ordinates Australia's use of several large overseas telescopes, including in Hawaii and Chile.
Ash Pennell, chairman of the Dunedin conference organising committee, said the Dunedin society had faced declining membership about 15 years ago, but that had since more than doubled, and the society's Beverly Begg Observatory was increasingly popular with visitors.
