I’m aware that under certain conditions, and viewed from the right place, some rainbows form a complete circle.
or at least, that’s what the Bad Astronomer says.
Question is: What are the conditions, and where is the place?
more importantly, and what I’m really looking for - does anyone know where I can get a photo of this Phenomenon?
btw, I’m not talking about ‘glorys’ - although I’ve never seen a phot of one of these either - but about real rainbows
OK, I have now seen a photo of a glory:
http://www.asite2see.com/gloryphotos/
but am still interested in a pic of a 360 rainbow (presumably it would be bigger and clearer than the glory?
I saw a circular rainbow once when I was on an airplane. The sun was on the opposite side of the plane from me and it cast a circular rainbow on the cloud cover below. It looked similar to the photos in the gloryphotos link above, except that there was a shadow of a little airplane in the middle. A very nice sight.
Here’s a badly cropped picture of a circular rainbow No description of conditions though.
you’re right - very badly cropped - in fact he’s managed to do it in such a way that you hardly notice the rainbow 
From that pic, it looks like you have to be directly above it to see a circle
Rainbows are caused by the refraction of light through the water droplets at a particular angle from the sun to the observer. A person standing on the ground looking up at the rainbow will always have some significant portion of the arc of light interrupted by the earth on which s/he is standing. To see a circular rainbow, you need to be flying.
The specific difference between a rainbow and a sundog (also called a glory) is that the rainbow will be at an angle of 40º to 42º from the observer (facing away from the sun) while the sundog will be directly opposite the sun extending only to an angle of a few degrees from the shadowed center.
I saw one once while in a helicopter flying over the western coast of Kau’ai. We were probably 3-4000 ft in the air and it was around 3 in the afternoon. Unfortunately, it was impossible to accurately picture because the helicopter was in the way and the rainbow was bigger than the arc of view of the camera.
You don’t necessarily have to be flying. I once saw most of a circular rainbow from the 5th floor of a residential highrise. As I recall it was foggy or misty below, but clear above the mist for the sun to shine down. The only reason I couldn’t see the whole rainbow was that I didn’t have access to the entire floor of the building, so one section of arc was obstructed.
It was not as spectacular as I would have thought, mainly because the other buildings in the area muddied the backdrop some. Mostly it was interesting because it hadn’t occurred to me that such a phenomenon is possible.
I didn’t attempt a photograph.
stypticus
I don’t think a sun dog is a glory. A sun dog is near the sun, a glory is near your shadow (thus opposite the sun.)
This page of Mount Washington weather has both a picture of a glory and of a sun dog.
I’ve seen circular rainbows quite frequently while flying, it helps if you live somewhere where rain is common. Elfoldo it sounds like you saw a glory, as a rainbow won’t have your shadow in the middle of it.
Topgun Fighter Tips:
If you can see a glory (normally appears on cloud oppsite the sun), “fly” it over to your opponent, this ensures that you are directly into the sun from him/her and can’t be detected visually.
You could do the same with your shadow but glories are generally easier to see.
This message is in no way meant to imply that I have anything to do with flying military aircraft.
You’re right. I was confusing glories and haloes.
Then, if you do not have an airplane handy, you can use a garden hose spraying water in a fine mist.
Just what I was about to say, sailor! I used to do this as a kid - I’d play with the garden hose and spray water and make a rainbow. Sometimes you could see the whole circle, but other times you’d have to "trace"it to see it - but it was always the same rainbow. I remember being 7 or so when I did this, and being able to explain why you can’t find the pot of gold at the end of the rainbow - I was always the more scientific type! Of course, for a while, I wondered by what trick the leprechauns were able to “break” the rainbow to get to the gold! hehe
