Telescope eyepiece

An eyepiece are builted with optical elements disposed at a certain distance from each other.
There are many types of eyepieces. Around the web and in wikipedia there are several types of eyepieces.

Some references:
http://en.wikipedia.org/wiki/Eyepiece
http://www.olympusmicro.com/primer/anatomy/oculars.html

Some cheap telescopes refer to the magnification they can get, however the most relevant measures are the telescope aperture, somehow relates to the image quality, by combining the focal length of the telescope and eyepiece we can calculate the power magnification.
There is a maximum magnification / minimum focal lengh recommended for the eyepiece

How to calculate the telescope apertue?
The aperture of the telescope can be calculated by dividing the diameter of the mirror (in mm) by the tube diameter (in mm).

How to calculate the magnification?
The magnification can be calculated by dividing the focal length of the rear mirror by the eyepiece focal length.
Since the rear mirror and the tube diameter are fixed, we can discover the maximum recomended magnification, given by the eyepiece. The smaller focal distance for the eyepiece is equal to the f-number of the aperture. If the telescope has an aperture of f/10, the smaller eyepiece is 10mm.

Online calculators:
http://www.astro.shoregalaxy.com/index_010.htm
http://www.rocketmime.com/astronomy/Telescope/MaximumMagnification.html

Building an eyepiece

I chose to build a simple eyepiece, similar to a Ramsden eyepiece, since it is the simplest and I get an excellent result, better than I expected.
The final magnification depends on the focal length of the eyepiece and the telescope mirror.
I used two plano-convex lenses of 30mm placed in opposite directions, separated by a distance of approximately half of the focal length (15mm), resulting in an eyepiece with approximately 15mm.

Building an eyepiece (click to enlarge)

Using this eyepiece, it's possible to put an adapter to attach the camera to the telescope.

An adapter to attach the camera to the telescope

Using this adapter I can photograph Saturn.

Picture of the planet Saturn

It's not like a NASA picture, but I like the result, inspires for more and better...