Object detection using webcam?

[Jose_VB]

I'm trying to write a software to detect an object in realtime using the webcam video as a source.
I've no idea about how to do it. I've seen some techniques that seems to filter some colors so it shows only the characteristic colors of that object.
I want to know to get some idea about how to start.
The object I want to detect is the Moon.

[dunfiddlin]

What do you mean, detect it? If the camera's pointing at it, it'll be the whitish thing. If it's not pointing at it, or there's cloud, or it's a new moon, it won't. I mean I could see some logic if you were tracking with a high definition camera on a long exposure but webcam?

[Jose_VB]

I use a webcam pointing to the sky, outdoors.
What kind of instruction can I use to show only a predefined amount of colours, without showing the others one?
I mean, If I use grayscale, to show for example all the grays between 50 RGB and 140 RGB colors?
(50,50,50) - (140,140,140)

[Shaggy Hiker]

Actually, the moon should be some seriously high contrast, so you might be able to apply a filter to the image where everything above X becomes white and everything below X becomes black. That would result in a two color image, and the largest region of all white should be the moon. As for the filter, it is technically fairly easy, as you would just have to look at the colors levels for each pixel, but there are probably MUCH faster ways to do that which I don't know about.

[dunfiddlin]

Actually, the moon should be some seriously high contrast

See, the trouble with that is, it's not true. When people think of the moon they always picture it full and shining down maximum intensity but it's actually a much more complex beast than that and in reality is darker than you ever perceive it to be. This is why I can't really see the point of using a webcam for this. It just doesn't have the sensitivity, especially in low light, necessary.

[Jose_VB]

See, the trouble with that is, it's not true. When people think of the moon they always picture it full and shining down maximum intensity but it's actually a much more complex beast than that and in reality is darker than you ever perceive it to be. This is why I can't really see the point of using a webcam for this. It just doesn't have the sensitivity, especially in low light, necessary.

So you recommend a high definition camera?
I know the colour can be a difficult task to control with the vb program, because sometimes the moon has different colors depending its position and the solar light.

[Shaggy Hiker]

A new moon won't show up at all, but for the others, I'd suggest taking a couple trial pictures. Can YOU see the moon in the picutes? If so, then it probably has high enough contrast. However, what dunfiddlin said was essentially correct: The moon looks bright to us because our eyes are pretty awesome. If you take a standard photo of the night sky you won't get a picture of stars because they are too faint to make it onto a fast exposure. You may not be able to see the moon at all without using some kind of long exposure setting, which a webcam may not be capable of. However, if you can see the moon in pictures taken by the web cam, then what I was suggesting should still work. If you can't see the moon in the pictures, then the camera won't work and no amount of programming can fix that.