Transparent sphere straight & level flight into the distance during air force air display in Australia.Last Saturday (02 Oct 2004) I was at RAAF (Royal Australian Air Force) base Amberley watching the model planes before the big guns came out. I saw past a model plane and spotted a clear sphere in the direction of Denmark Hill as viewed from a little north of the old control tower e\west of the main strip. It seemed far away and was traveling east-South East straight and level flight. Its size was 3mm diameter as measured with the fingers at full arms length. Its height was about 20 degree above horizon. Its appearance was of a glass ball in that I could see the complete spherical outline with the left side being slightly brighter. This agrees with where the sun was (not sure of the time as I did not take my watch that day, however the program (I have a copy) states that the model aircraft were on from 10:41am to 11:05am. Here is more on the actual sequence and timing of my observation: Spotted it while looking at a model (large model, 1-2 meters across) from a distance of about 50 meters.I stopped following the model (from left to right) and watched it intently for about 5-8 seconds and then I deliberately looked away while closing and rolling my eyes.Looked back; I could not see it straight away: perfectly clear sky; nothing to focus on anywhere so I strained and then I caught it (10 seconds later) again, now it was smaller and seemed further away and was blending into the blue of the sky.It only dawned on me then that I had my 35mm SLR and a 200mm lens with me so I quickly opened the bag, fitted the 200mm (took about 15 seconds) looked up and tried and tried to see it again but could not. I raised the camera up and looked through the lens (only slight advantage for the eyes in object size but screens out side light) but to no avail. What a bummer! If only I had prepared my camera upon arrival I reckon I would have caught it and at a size that would blow up nicely! My feelings are as follows: It was not a balloon due to its straight and determined flight path, its speed, and its size which is difficult for me to work out though it gave me the immediate impression that it was large, say 3 plus meters across. This impression was formed due to my experience of observing aircraft at altitude and distance (ex RAAF and keen follower of Air Force displays) and my rather good view over the Amberley area from my street in Sadliers Crossing.It seemed rigid, as if it was a solid globe structure.It did not immediately cause me to think it was unusual as I have seen much in the way of junk flying around in the sky especially paper and plastic bags! It was the fact that it was so straight and purposeful in flight that grabbed my interest. Logical answers. Nuh. Can’t think of any. And I’ll tell you what it reminded me of, early in the peace - that shot of the ball flying across the fields in the crop circles documentary that is available on DVD! Except the object I saw was much clearer than the one as presented on that DVD and traveled dead straight! That’s it!!!