Professional Astronomical Refractor ... telescope for adults astronomy beginners to explore nature and the universe 90mm Large Aperture: The astronomy telescope has an 800mm(f/8.88) focal length ...

This refractor telescope is perfect for beginners who ... thanks to their typically long focal length, but unfortunately, they do have a tendency to suffer from chromatic aberration.

There are two types of telescopes: a lens-based refractor and a mirror-based reflector ... be calculated by dividing its objective lens's focal length by the eyepiece's focal length, both ...

Well, any of us who has ever looked through a telescope could say the same, for the two principal types in use today were developed by giants: the refractor ... to make the focal length of the ...

9.53 inch Clark Refractor The main telescope is the original 9.53 inch refractor built in 1885. The objective lens was made by Alvin Clark and Sons of Cambridge, Massachusetts, and has a focal length ...

the Bresser SpaceExplorer refractor telescope comes with a mount, tripod, and multiple accessories to fuel your fascination with the night skies. It boasts a 900mm focal length which works well ...