Sage-Tips

What effect does a Barlow lens have on what you see through a telescope?

Steve says: “A Barlow lens is an optical tube containing lens elements that diverge the light passing through them. Inserting a Barlow lens into the light path of any type of telescope increases the effective focal length, usually by doubling it, although some designs have an even greater effect.

What is the purpose of the Barlow lens?

In microscopy the Barlow lens is used to increase working distance and decrease magnification. The lenses are “objective lenses” that are mounted in front of the microscope’s last objective element. Barlow lenses for microscopes can be found with magnifications ranging from 0.3× to 2×.

What difference does a Barlow lens make?

To put it simply, Barlow lenses are a cost-effective way to increase the magnification of your eyepieces. Their effect is to increase the magnification of any eyepiece used with them, usually 2 or 3 times. As you’d expect, a 2x Barlow doubles your eyepiece magnification, whilst a 3x trebles it.

Does a Barlow lens decrease quality?

Most barlows should improve the outer field sharpness of eyepieces that have problems with sharpness at the field edge. A truly bad barlow will degrade the edge performance of good eyepieces.

Can you use a Barlow lens with a diagonal?

You can use a standard Barlow in a refractor, SCT, or other scope that uses a diagonal, either by inserting it between the telescope and diagonal or by (carefully) inserting it between the diagonal and the eyepiece. (The danger is that the long Barlow may protrude too far into the diagonal, damaging the mirror.)

Can you use a Barlow lens on a reflector telescope?

That means a 32mm Plossl with a 2x Barlow delivers a similar magnification to a 15mm Plossl without a Barlow, but the 32mm eyepiece is much more comfortable to look through. Barlow lenses also allow the use of simpler eyepiece designs with fast focal-ratio refractors or reflectors.

How does a Barlow affect focal ratio?

By increasing the focal length of a telescope, a Barlow also increases its focal ratio. For example, using a 2X Barlow with a 250mm f/5 telescope (focal length 1,250mm) effectively converts that scope to a 250mm f/10 scope (focal length 2,500mm).

What does a Barlow lens do in a telescope?

It increases the telescope focal length. A Barlow lens increases the power of your telescope by increasing the telescope focal length as it creates a more acute diverging cone of light. It can help get you better views of the details of planets. For eyeglass wearers: A Barlow lens can increase the eye relief of a given eyepiece.

How do you increase the magnification of a Barlow lens?

One way to increase the magnification of your telescope is to use an eyepiece with a smaller focal length, and this is what we do when we use a high powered eyepiece. A Barlow Lens, however, increases the magnification by effectively increasing the focal length of the telescope instead.

What is the difference between a 2x and 3x Barlow lens?

Thus, giving us the ability to use a wider field of view for lenses to achieve the same magnification. A 2X Barlow lens doubles your telescope’s focal length while a 3X Barlow lens triples it. For example, a 20mm eyepiece on a telescope with a 1000mm focal length gives a magnification of 50.

Why do Barlow lenses get dimmer over time?

With a Barlow lens, because of the higher magnification and optical resolution, you often need a very precise Polar Alignment and/or a guiding system. Because it is a diverging lens, the cone of light is spread on a larger area, so the image gets dimmer with the increase of the magnification.