It will be "eyes up" Friday and Saturday for those interested in viewing the rings of Saturn.
Sutherland Astronomical Society president Ken McEwen said other objects visible on the two nights are expected to be craters on the moon and Saturn, star clusters and a number of deep-sky objects including nebulae.
There will be a 41-centimetre Selby and a 35-centimetre Napier telescope plus a variety of portable telescopes on the field on the two nights.
Astronomy lectures will be given and there will be special guests from the US space camp.
There will be hot and cold food and drinks, books, posters and gifts on sale.
The society is operated by volunteers.
Members of the public are invited to visit the Green Point Observatory at the intersection of Green Point and Caravan Head roads, Oyster Bay, with viewing from 6pm to 11pm.
People should wear warm clothes.
Bookings are not needed, with charges of adults $10 children $5, family $20, concession $5.
Details: www.sasi.net.au