Re: Can refractor telescopes have different sized third lenses?

Hello Ben

I think that this would be a great science project. My first telescope was a refractor and I still use it from time to time. I am not sure if I understand about the third lens in a refractor. Most refractors just have two lenses, the objective lens in the front to gather the light and an eyepiece that focuses the light onto the retina. By changing the eyepiece we can change the magnification of the image and we can insert a corrector that will invert the image a second time so it appears right side up to our eye. Since you want to investigate this as a science fair project, I suggest that you get several magnifying glasses and see for yourself what will happen.

Remember that in an astronomical telescope, each time we pass light through a lens it gets bent again and that can cause problems with the image. If the lenses are not great quality the image can be degraded and less distinct. What we are looking at is usually very faint and we want to distort the light as little as possible.

I have included several links that should help you with the research. Good luck.

http://www.hows tuffworks.com/telescope.htm/printable

http://www.howstuffworks .com/telescope1.htm

http://www.sal .wisc.edu/SpacePlace/optics/optics.html

http://Sky andTelescope.com/howto/scopes/article_241_1.asp

http://es.rice.edu/ES/humsoc/Galileo/Student_Work/Astronomy96/mtele scope.html

[Moderator's note: Ben, I'm sure you know this, but just a reminder to others: DON'T use a telescope or magnifying glass to look at the Sun!!]