Comparison Between 10mm and 25mm Eyepieces- A Complete Guide

If you’re an amateur astronomer, you know that there are a lot of different eyepiece sizes to choose from. Two of the most common sizes are 10mm and 25mm, but which one is better? In this article, we will break down the differences between the two and help you decide which one is right for you.

Comparison Between 10mm and 25mm Eyepieces

Below are some key features to consider when deciding which one is best for your needs.

Field of View

The field of view (FOV) describes how large an area can be seen through an eyepiece at any given moment. A wider FOV means more sky can be seen in one glance; think binoculars vs telescopes here. Generally speaking, 10 mm lenses have a narrower FOV than 25 mm lenses, meaning less sky can be seen at once with a 10 mm lens versus a 25 mm lens.


Magnification describes how much bigger an object appears when viewed through an eyepiece compared to its actual size in the night sky. Both 10 mm and 25 mm lenses offer high levels of magnification, however, due to their larger size and wider FOV, a 25 mm lens will typically provide higher levels of magnification than that offered by a 10 mm lens.       


As mentioned earlier, larger lenses can gather more light than smaller ones; this means that images viewed through a 25 mm lens will usually appear brighter than those viewed through a 10 mm lens due to their ability to collect more light from distant objects in space.

Factors to consider before buying 10mm & 25mm eyepieces

Eyepiece selection is a critical factor when it comes to enjoying your time under the stars, which is why this guide will break down the important factors that should be considered before making a purchase. 

Eye Relief & Eye Widths 

The first point to consider when buying eyepieces is eye relief. This refers to the distance between your eye and the lens of the eyepiece. When using an eyepiece with low eye relief, your eye needs to be very close to the lens for it to be effective—which can cause discomfort for those who wear glasses or contact lenses. With higher eye relief options, however, there is more space between your eye and the lens, making them better suited for people who wear glasses or contacts. Additionally, make sure that you take into account the width of your eyes to get maximum comfort while using any given eyepiece.  

Field Of View & Magnification  

Another factor that should be considered before purchasing eyepieces is a field of view (FOV). FOV refers to how much sky you can see through your telescope at any given time—the bigger the number, the wider and bigger the image will appear in your telescope’s viewfinder. Generally speaking, 10mm and 25mm eyepieces offer great FOVs—but keep in mind that as magnification increases with these eyepieces, FOV decreases accordingly.

So if you’re looking for a wide view of the night sky then keep in mind that lower magnifications are best suited for this purpose. Additionally, keep in mind that different telescopes require different levels of magnification; so if you’re planning on using multiple telescopes then make sure each one has compatible eyepieces with its respective magnification requirements.  

Price & Quality  

Finally, consider price and quality when selecting 10mm & 25mm eyepieces for your needs. As mentioned earlier, higher magnifications decrease both FOV and comfort; therefore some cheaper models may not provide satisfactory results due to their lack of luster construction materials or lower quality optics/lenses used during production.

Make sure you do research on any given model you’re considering buying—read reviews from other users who have used it and compare prices against other brands/models to ensure maximum value per dollar spent on any particular model! Overall, good quality doesn’t necessarily need to come at a high cost – do your research beforehand.

You can check reviews of telescopes here


When it comes down to it, both 10mm and 25mmeyepieces offer their unique benefits depending on what type of telescope you have and what type of views you want out of it. If you want bright views with lots of detail then go for the larger size (25MM) if you want wider fields then go for the smaller size (10MM). Ultimately it comes down to personal preference so take your time testing out different options before settling on one! Thanks for reading our comparison between 10mm vs 25MM eyepieces – happy stargazing!


Q: What does “10mm” or “25mm” refer to in terms of eyepieces?

A: The number refers to the diameter of the lens inside the eyepiece. A 10mm lens has a smaller diameter than a 25 mm lens.

Q: What type of telescope do I need for each type of eyepiece?

A: Generally speaking, 10 mm lenses are designed for telescopes with slower focal ratios (f/6 or slower). Meanwhile, 25 mm lenses are designed for telescopes with faster focal ratios (f/5 or faster).

Q: Does size matter when it comes to choosing an eyepiece?

A: Yes! The larger the lens size, the brighter your images will be in your telescope. This is because larger lenses can gather more light than smaller lenses.

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