The government of the United States has never acknowledged its existence, however it has been identified by amateur observers and through leaked information.

Following the satellite's retirement these modifications ceased to be effective, allowing it to be found by amateur observers.

Data were also collected from a network of amateur co-operative observers who corresponded by mail.

It was unusual for him, the most theoretical of theoreticians, to be attending a meeting of amateur observers.

Ferris's profiles of professional and amateur observers, rendering their special experiences, are particularly rare and interesting.

She coordinated many important observing programs between amateur observers and professional astronomers.

Think of me as an interested amateur observer.

George Alcock is the outstanding amateur observer of this century.

However, many planetary successes come from amateur observers with small and medium-aperture telescopes.

Collaborations between researchers and amateur observers is successful in astronomy.