Higher magnifications are not always the best decision. If you have a purpose to observe the night sky and look at many stars at once, a low magnification telescope will be better than a more powerful device because it is more comfortable to use. It also gives a wide picture and a bright image.

It also happens that powerful lenses are useless and work like their cheaper analogs if a telescope is not fit for them.

To clarify what telescope, lenses, and other accessories are enough for your purposes, use the telescope magnification calculator.

Contents

- 1 Focal length and how to use it
- 2 Telescope focal length
- 3 Eyepiece focal length
- 4 Barlow lens
- 5 Maximum usable magnification
- 6 Frequently asked questions
- 6.1 How do you calculate magnification on a telescope?
- 6.2 What is a good magnification for a telescope to see planets?
- 6.3 What does 40x mean on a telescope?
- 6.4 Is a 60x magnification telescope good?
- 6.5 What can I see with a 200x magnification telescope?
- 6.6 What is the max magnification of a 6-inch telescope?

- 7 Summary

## Focal length and how to use it

So, you do not know the telescope magnification and want to find it out by calculations.

There is the formula:

**Telescope’s focal length / Focal length of the eyepiece = The magnification**

For instance, if the focal length of the telescope is 1500 mm and the focal length of the eyepiece is 10 mm, the telescope goes up to 150x magnification.

Now it’s time to clarify what a focal length means.

## Telescope focal length

It is the distance the light goes through a telescope. It is measured from an aperture (an entrance hole) to an exit pupil (eyepiece) of a device.

Usually, the information about a focal length is not marked on an eyepiece.

If you do not know this characteristic, try to find the information in the manual or on the Internet. The official site of the manufacturer is the most reliable source.

**Telescopes with shorter focal lengths can give a less magnification** than the other ones.

## Eyepiece focal length

This characteristic means the distance between the principal plane and the spot where all the rays intersect at one point. Most likely, you can easily find the information on the given eyepiece. Eyepiece focal lengths are usually written down in millimeters.

Any **eyepiece with shorter focal lengths can give higher magnification **than the others.

## Barlow lens

Such an accessory can be placed between the focuser of your telescope and its eyepiece. A Barlow lens gives more magnification. For instance, with a 2x Barlow, the magnification of 50x can become 100x.

Meantime, a 3x Barlow lens makes 150x, etc.

By the way, there are other accessories like a focal reducer. It cuts the focal length instead of increasing it.

If you use this accessory, you should **keep in mind the effect of the Barlow lens or focal reducer** in your calculations.

## Maximum usable magnification

This characteristic is important to count because high-quality magnification can be done only within the maximum usable magnification range.

Otherwise, you may get a blurred picture.

To calculate magnifications, use the formula:

**Telescope’s aperture (in inches) x 50**

or

**Telescope’s aperture (in millimeters) x 2**

For example, if the telescope aperture is 60 mm, the device allows you to watch objects clearly at 120x magnification.

## Frequently asked questions

### How do you calculate magnification on a telescope?

Divide the telescope’s focal length (the distance between the aperture and exit pupil) by the same characteristic of the eyepiece.

### What is a good magnification for a telescope to see planets?

Usually, it requires 200x or 250x. Sometimes, 100x is enough.

### What does 40x mean on a telescope?

It means a magnification.

### Is a 60x magnification telescope good?

It is good for watching the night sky, but you need higher magnification to observe the planets.

### What can I see with a 200x magnification telescope?

It is a powerful device. It allows us to see even the planets.

### What is the max magnification of a 6-inch telescope?

According to the special formula, it is 300x (6 x 50 = 300).

## Summary

To calculate the telescope magnification, use the magnification calculator:

**The Magnification = Telescope’s focal length / Eyepiece’s focal length**

Remember that the maximum usable magnification matters. If the magnification you have got is higher than the telescope’s maximum, the image won’t be good.

If you need to read about telescope magnification calculator, please read our article.