What is the relationship between eyepiece focal length and telescope magnification?
The calculation is simple: divide the focal length of the scope by that of the eyepiece. So, if you have a scope with a 1,200mm focal length and a 20mm eyepiece, your magnification would be 60x. The smaller the focal length of the eyepiece, the greater the resulting magnification on any given telescope.
What is the focal length of a telescope eyepiece?
about 3 mm to 50 mm
Amateur astronomers tend to refer to telescope eyepieces by their focal length in millimetres. These typically range from about 3 mm to 50 mm.
What does D and f mean on a telescope?
The aperture of the objective lens of this simple telescope is D. The focal length of the objective lens if F. The focal length of the eyepiece is f.
What is a 10mm telescope lens good for?
10mm – 13.9mm Telescope Eyepieces: These are fine to use across all focal lengths and offer great background darkening capabilities for studying planetary nebula, small galaxies, planetary details and lunar details.
Is a 10mm or 20mm eyepiece more powerful?
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 focal length eyepiece do you need?
The most common and time-tested rule of thumb suggests not exceeding a magnification of about 50x per inch of aperture of your scope. For a 4″ telescope, for example, you should stick to less than 200x with your shortest focal length eyepiece. Any higher and the view will become unacceptably dim and less sharp.
What is the best focal length for a telescope?
A shorter focal length telescope will be more suited to wide field views of the stars. A good all round first telescope should have a focal length of around 1000mm to 1200mm. All refracting telescopes use a glass lens as their primary focusing unit.
What is a good f ratio for telescope?
Focal Ratio – Faster, Brighter, Smaller A long focal ratio implies higher magnification and narrower field of view with a given eyepiece, which is great for observing the moon and planets and double stars. For such objects, a focal ratio of f/10 or more is ideal.
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.
What is the best focal length for telescope?
What eyepiece is best for planets?
Ultra-short focal length (2-4mm) eyepieces provide very high power magnifications and are best for observing the planets and the moon on shorter focal length telescopes.
Is a 70x magnification good?
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.