Can I build a telescope with a lens from a CD-ROM as eyepiece? I saw some article on the web about making an eyepiece of a telescope with the lens from a CD-ROM. Will this really work? I have an objective lens of 100 cm focal length. What will be the magnification if I could make a refractive telescope? Can I see the planets and moon with that? Can anyone suggest the arrangement of the lenses?
This article gives a construction guide for how to make an eyepiece using a CD ROM player lens: How to make an eyepiece for a telescope.

As to what the focal length of your  eyepiece will be, you can refer to this paper, in particular Figure 1 from which I derived the following relation:

$f=0.73r$

where $f$ is the focal length of your lens, and $r$ its radius (this is a rough approximation, of course). So given the fact that a typical CD drive lens is about 5mm in radius, its focal length will be only a few millimeters.

Now, assuming the focal length of your telescope is 1000mm, the magnification will be a few hundred times. What you will be able to see with that depends on the width of your objective lens and how well you will have built your eyepiece, but you should probably be able to see the Moon with your custom eyepiece. As for the planets, it will be hard to get something good given how much you are magnifying—not impossible, but be aware that magnifying several hundred times requires a good weather, a good telescope and a good eyepiece.