webcam lens?

[Darkstar_1]

Hi, here is what may seem a dumb question; Why do you need to take the lens off a webcam for astrophotography? Is it due to focusing issues or something else? Thanks.

dark skies, Den.

[themos]

You don't have to. You can leave it on and do what is called "afocal" photography. In that, the telescope forms a real image (that is, you could actually see it if you put a white card at the right spot) and then you focus the webcam lens on that image.

The reason we usually take out the lens is that the less glass in the way, the better the image. And since you can make an image on the webcam sensor without the lens (the telescope produces the image and the sensor is put where that white card would be), we do it that way.

[michael8554]

Okay, switch on your webcam with its supplied lens attached and point it at the moon

What do you see on your screen?

A dark sky with a tiny white dot (the moon) in it

So how do you make the image of the moon bigger?

You replace the standard lens with a telephoto (long focal length) lens

A BIG telephoto lens

And a telescope is just that, a big telephoto lens

That's why you take the lens off.