All telescopes have a fixed focal length, just like lenses on a camera. So a 20mm focal length will give you a wider field of view than say a 300mm. You will also notice that with a 300mm you get a larger image of the subject, be it a person or animal or even the moon.
Is a 20mm eyepiece good?
A 20 mm is useful just as a 13 mm is useful in most any telescope but I'm not sure "all purpose" is a good description. My telescopes range in focal length from under 400 mm to about 2800mm, a 20mm is not a planetary or high power or even mid-power eyepiece in any of them, it's a low to mid power deep sky eyepiece.
How many mm is a good telescope?
The aperture's diameter (D) will be expressed either in millimeters or, less commonly, in inches (1 inch equals 25.4 mm). As a rule of thumb, your telescope should have at least 2.8 inches (70 mm) aperture — and preferably more.
What can you see with a 20x telescope?
First Planets: all the planets and some asteroids. Mercury like a point, Venus with the phases, on Jupiter the cloud bands and 4 satellites, maybe not the Great red spot, on Saturn the rings and Cassini division, Uranus and Neptune like blue-green dots.
Is a 10mm or 20mm eyepiece more powerful?
The most important eyepiece characteristic is focal length. … This means that a smaller number on an eyepiece gives a higher magnification. A 10mm eyepiece would provide twice as much magnification as a 20mm eyepiece. It also means that the same eyepiece gives different magnifications on different scopes.
What can you see with a 25mm telescope?
25mm – 30.9mm Telescope Eyepieces: These are extended field eyepieces for longer focal length – good for large nebula and open clusters. For shorter focal length, they are fantastic for large objects such as the Orion nebula, views of the full lunar disc, large open clusters and more.
What can you see with a 100mm telescope?
What Can You Expect From 100mm Telescopes? (With Photos)
- The maximum magnitude of a 100mm telescope is 13.6. For reference, the Moon has a magnitude of -12.74 and Mars has a magnitude of -2.6. …
- The Moon. The Moon looks amazing in these telescopes. …
- Mars. …
- Venus. …
- Jupiter. …
- Saturn and Neptune. …
- Pluto and Dwarf Planets. …
- Mercury.
What is considered a large telescope?
Finally, any telescope with a lens or mirror larger than 10 inches is “large.” More large telescopes are in use today than ever before.
What can you see with a 700mm telescope?
With a 70mm telescope, you will easily be able to see every planet in the Solar System. You will also be able to take a great look at the Moon and clearly distinguish most of its recognizable features and craters. Mars will look great.