On the evening of May 17th in southern Canberra Australia I observed a very bright light in the sky for about 15 minutes, starting at 5:20 pm finishing at about 5:35 pm. The sky was cloudless with no wind. I first observed it as a very bright light in the NNE on the way home in Monash a suburb in the south of Canberra. It was low in the sky, about 20 degrees up. It was bright yellow, much brighter than Jupiter which was also visible. Over the period of observation it gradually dimmed through orange to red but did not appear to move. The rate of dimming as roughly similar to the loss of daylight.
A post on a friend’s FB page show’s its naked eye appearance and gives an idea of its brightness
https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xpf1/v/t1.0-9/13227171_10153846033058124_5571008360296202243_n.jpg?oh=df29566982ae03d878a0a5f1f26814e7&oe=57E0171C&__gda__=1474459491_f7075b899e2433788686e6e9e420e0c9I looked at it through my 60 mm refractor at magnifications of 20X though to 60X. The object was lenticular, rather like an eye, in that the centre was darker and the ends brighter. There was a very faint line extending down from the bottom, also orange, for a short distance. It did not appear to move in the telescope field of view. Angular diameter was perhaps half as much again as Venus at maximum elongation.
A local amateur astronomer also photographed it
https://twitter.com/Astro0Glen/status/732858361490903040, I came across these photos the next day.
My interpretation was this was some kind of large balloon of translucent material, fully inflated. Which would explain the appearance and shape. It was lit by the setting sun, which explains the colour and the dimming.
Later reports indicated that it was visible at least as far north as Bathurst, more than 200 km NNE of here.
This being the 21st century I posted the observation on a space related FB group and within minutes was referred this link
http://www.nasa.gov/feature/nasa-super-pressure-balloon-begins-globetrotting-journey/ The location matched exactly.
Some people have told me the explanation has spoiled what they saw. I think the fact I saw an unmanned balloon with half a million cubic metre volume more than 30 km up, relecting light from a sun that was below the horizon, carrying a payload the size of a bus, that will spent at least three months circling the globe studying events invisible to our senses thousands of light years away and thousands of years in the past, amazing.
The moral is that without the telescope it would have remained a probable UFO (although I might have suspected a balloon, based on previous knowledge and experience). With the telescope it would have been a probable IFO. Only with the resources of friends on FB did it become a IFO.
Amusingly, one federal government office received reports of a UFO sighting and questions of "what were they going to do about it?"
