After that he travelled overseas for four years, including to African countries where he saw "some pretty awful sights". He returned to New Zealand and spent three and a half years as an outdoor instructor for Outward Bound in the Marlborough Sounds.
Then he became a Lands & Survey ranger in national parks, and applied to work in Antarctica again. He was deputy leader at New Zealand's Scott Base for four months in the 1977-78 summer, then leader for the next seven months.
He remembers seal counts, driving Ed Hillary's tractor and going to the South Pole and the Russian base at Vostok.
It was the early days of the New Zealand Antarctic programme, and his slides are a valuable record. They had to be sent to Christchurch to be developed and he didn't get to see them for weeks or months after they were taken.
Back in New Zealand the Conservation Department was formed in 1987, and Mr Lythgoe became a ranger, first at Pipiriki, then in Whanganui.
He often worked with volunteer groups and he carried on tramping in his spare time. His favourite is the Southern Alps, and especially Mount Aspiring National Park, with its alps, bush and rivers.
He took early retirement, aged 60, to do more tramping and travel. He's now 73, and Parkinson's disease has stopped him carrying a full backpack.
"I've had to give up what I love."
Mr Lythgoe made one more trip to the Antarctic about five years ago, as a tourist, travelling by sea. He found Scott Base bigger and more comfortable than in the 1970s.
"It went from one star to five stars. We had pretty basic facilities, with poky little perspex windows. Now they have vista windows, and quiet areas with lounge chairs."
He said it was great to go back, even for a quick visit.
His slides and photographs are now being assessed, Alexander Turnbull Library curatorial services leader John Sullivan said. The Antarctic images are especially likely to be kept.
"I can say that the Antarctica is definitely part of our collecting scope, and we are keen to build the strength of our collections in this area."
Once the images have been accepted people who are registered for the library's online database can ask to look at them in one of the library's reading rooms.
The Alexander Turnbull is also progressively digitising parts of its collection, including its Antarctic images.