what telescope did the astronmers have that discovered alot of things

[caleb]

Im talking design, focal lengths and apeature diametres, what were there eyepieces and did they have barlows.
And when I mean discoverd, i mean along time ago, like Gallileo and his mates.

[leon]

Gallileo and his mates if you like that term, started off with very simple instruments, which consisted of nothing more than a tube with a pair of spectacle lenses on either end, which he could move in and out to get a crude focus.

leon

[Jarrod]

simple long focal length, small apeature refracters.

up to 1" (25mm) apeature, with up to about 1m focal lengths. in Galileo's time (early 1600's) that was considered pretty big. the magification was set at around 20x, as interchangeble eyepieces were not around. design wise, very simple. a tube with a lens at each end. well, two tubes. one tube inside the other, so that the length could be adjusted to focus. aberrations and glass quality issues of all sorts were a big problem, so for a while people were more concerned with building higher quality telescopes then larger telescopes.

these telescope were enough to see the moon's of jupiter, observe the surface of earths moon, and also to project sunlight onto paper to observe sunspots. it was also enough to allow people to see that there were more stars in the sky then they could have ever imagined. and see that some stars were actually "clouds".

then 70 or so years later Newton came along with the idea of using curved mirrors instead of lenses, so then the story kind of splits two ways... refractor vs reflector.

j

[edwardsdj (Doug)]

Galileo was actually a master optician of his time. Particularly considering the glass of the period was so poor. He made about 100 telescopes of which about 10 were good enough for astronomical observation. He ground all the lenses himself.

I believe he discovered the Galilean satellites of Jupiter with an objective of about 35mm stopped down to 15mm and a simple eyepiece (single concave lengs) providing a magnification of about 30x.

I believe most (if not all) of his telescopes had plano-convex primaries which are flat on one side and convex on the other.

With these instruments he discovered moons orbiting Jupiter, the phases of Venus, realized the Milky Way was composed of many faint stairs and saw the rings of Saturn (though he described them as "handles").

Many others tried to make telescopes but Galileo was the master in his time.

Have fun,
Doug

[Karlsson]

Caleb,

If you're interested in this part of history, I can recommend reading Fred Watson's book 'Stargazers', ISBN 1-86508-658-4. It addresses your queries very well, and many more.