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Eyepiece 101

Eyepiece 101

Eyepiece 101

1. How to choose the eyepiece?

There are three most basic technical indicators: focal length, apparent field of view, and exit pupil.

1.1 Focal length

The structure of the eyepiece is complex, so the focal length here refers to the composite focal length, that is, an eyepiece is equivalent to a single convex lens with a focal length. Observing under the same telescope, using eyepieces with different focal lengths, will have different magnification effects.

Magnification = focal length of objective lens/focal length of the eyepiece

Now here’s the point.

There is a limit to the magnification of the telescope, which is about twice the telescope’s aperture, so you need to calculate the magnification with the eyepiece, and do not exceed the limit magnification of your telescope.

Let’s take a look at SV503 102mm ED. This telescope’s focal length is 714mm and the maximum magnification of this telescope is 204x, which would be achieved with a 3.5mm eyepiece.

1.2 Apparent field of view

The field angle can be observed when observing the target through the eyepiece. This is the size of the "black circle" that is often referred to. Generally speaking, the larger the apparent field of view, the more immersive it is. Just imagine the VR.

1.3 Exit pupil distance

The distance from the last lens surface of the eyepiece to the focal plane of the eyes. Eyepieces with a longer exit pupil are more suitable for people who wear glasses.

2. What do we have?

2.1. PL

Plössls, also known as PL, uses two sets of cemented lenses, each cemented lens is convex and a concave cemented together. The advantage of a cemented lens is that it can greatly reduce chromatic aberration. It has also become the standard one of the current astronomical telescopes. Almost every manufacturer will equip the telescope with PL eyepieces as standard.

2.2 Svbonys PL

SV207 1.25 inch Super Plossl 8/15/25/30 mm 50-Degree Eyepiece

The SV207 series are classic Plossl eyepieces that offer higher performance than the majority of eyepieces supplied with telescopes.  

SV131 1.25" Plossl 6/12/17/25/40mm Eyepiece 48-Degrees

SV131 Eyepiece has five focal length sizes, meeting different needs. It has a high-quality image for its fully coating in each glass. Besides, the 48-degree field of view allows you to see more bright images. The all-metal mirror structure will give you comfortable touching. M28.5*0.6 threaded supports 1.25-inch filter adapter installation. The lens edges and inside the barrel are light-removed, which can prevent stray light. The 4-element in 2 groups optical structure brings the great clear images. This eyepiece will show you a brilliant viewing.

More eyepiece.

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