<p>A Barlow lens doesn't multiply the focal length of your eyepiece, it multiplies the focal length of your telescope. Example:</p>

<p>Let's use a telescope of 1000mm focal length. 8" f/5 Newtonian, for example. And you have a 10mm and 25mm Eyepiece and a 3x barlow.</p>

<p>Then the barlow turns these 1000mm into 1000 x 3 = 3000mm focal length.</p>

<p>The magnification is always: <strong>FL telescope / FL eyepiece</strong>. That means, with the barlow, you have 3000 / 10 = 300x magnification or 3000 / 25 = 120 x magnification. Without barlow it's 100x (10mm) and 40x (25mm)</p>

<p>An eyepiece is a magnification lense. You can put two eyepieces on top of each other. You just won't see anything useful with that. Lens systems are carefully designed to result in an eyepiece that works.</p>

<p>Eyepieces with a bigger focal length give smaller magnification.</p>

CC BY-SA 3.0
2018-03-13T23:32:08.233Z
2018-03-13T23:32:08.233Z
Haunt_House
<p>You will get the maximum magnification by using the 10mm eyepiece with the barlow lens.  You cannot connect 2 eyepieces in the way you suggest, but even if you could add the 10 and the 25 to get a 35mm, that would give lower magnification, as I explained in a previous answer.</p>

CC BY-SA 3.0
2017-12-16T11:47:04.073Z
2017-12-16T11:47:04.073Z
Dr Chuck
<p>how to connect two eyepieces together with the x3 Barlow lens</p>

<p>I have 10mm,25mm, and x3 Barlow. Is there any way to connect them together to archive the maximum magnification of 105mm?</p>

CC BY-SA 3.0
2018-01-15T13:06:47.870Z
linked: https://astronomy.stackexchange.com/a/23971/11264
J. Chomel
<telescope>
how to connect two eyepieces together with the x3 Barlow lens
Eng. Sultan
# how to connect two eyepieces together with the x3 Barlow lens

(Asked by: username_0 on 2017-12-16)

how to connect two eyepieces together with the x3 Barlow lens

I have 10mm,25mm, and x3 Barlow. Is there any way to connect them together to archive the maximum magnification of 105mm?

**Tags:** telescope

> **Comments:**
> **username_1**: linked: https://astronomy.stackexchange.com/a/23971/11264  

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## 2 answers

### Answer by username_2 on 2018-03-13. Score: 1

A Barlow lens doesn't multiply the focal length of your eyepiece, it multiplies the focal length of your telescope. Example:

Let's use a telescope of 1000mm focal length. 8" f/5 Newtonian, for example. And you have a 10mm and 25mm Eyepiece and a 3x barlow.

Then the barlow turns these 1000mm into 1000 x 3 = 3000mm focal length.

The magnification is always: **FL telescope / FL eyepiece**. That means, with the barlow, you have 3000 / 10 = 300x magnification or 3000 / 25 = 120 x magnification. Without barlow it's 100x (10mm) and 40x (25mm)

An eyepiece is a magnification lense. You can put two eyepieces on top of each other. You just won't see anything useful with that. Lens systems are carefully designed to result in an eyepiece that works.

Eyepieces with a bigger focal length give smaller magnification.


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### Answer by username_3 on 2017-12-16. Score: 1

You will get the maximum magnification by using the 10mm eyepiece with the barlow lens. You cannot connect 2 eyepieces in the way you suggest, but even if you could add the 10 and the 25 to get a 35mm, that would give lower magnification, as I explained in a previous answer.


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