I took this photograph in 1987 in Golden Colorado at dusk. I was in the front yard taking photos of my kids when this flash happened in the sky so I took a quick photo with my 35mm camera. It lasted only about 20 seconds and then it was gone. Can anyone help me try to explain what might have happened. I do not need any UFO or ET explanations as to what it is. I would like to find a scientific explanation.

<img src="/attachment.php?attachmentid=3689&stc=1">

maybe aurorae?
http://www.edmontonrasc.com/auroraephotos.html

If you were facing North, I'd say it was the Northern Lights, although I don't know if Colorado is far north enough to see them.

What bothers me is the colour in the image though, ... the 'aurora' is purple, as is the uniform streak down the side of the image, leading me to believe it's false colour. Usually the background colour from any scanned image is the white, as the lid of a scanner is nearly always white. There's also some coloured streaking along the top of the image, which I presume wasn't actually present in the sky, and is an artefact of some kind. It being purple too, I'd suggest this adds credibility to the idea that the colours are way off.

So, what I'd say this was, was a fog bank, illuminated by some light source (Not camera flash or the tree should be lit up.) maybe car headlights, and the colour was altered, to make it look more weird.

that "object" is atually a reflection from the top of a tree, if you look closely you con see the rest of the tree blurred out by autofocus and light filtering

I took this photograph in 1987 in Golden Colorado at dusk. I was in the front yard taking photos of my kids when this flash happened in the sky so I took a quick photo with my 35mm camera. It lasted only about 20 seconds and then it was gone. Can anyone help me try to explain what might have happened. I do not need any UFO or ET explanations as to what it is. I would like to find a scientific explanation.

Can you tell us anything else? Was the lighting steady, or did the intensity waver? Are you sure it actually happened, and you are not trying to get us to identify a faked image? :) Was there an accompanying sound?

If you were facing North, I'd say it was the Northern Lights, although I don't know if Colorado is far north enough to see them.

We once got Northern Lights in our town (42 degrees latitude). So It could be northern lights.

Whatever it was was lit from behind. I think I agree with phlogistician about the fog. And it DOES look like false color. Why did you withhold that information?

Provide exact (as possible) time and date, and send it to NASA for evaluation.