Are you considering the Celestron SkyMaster Binoculars but are not quite sure which spec is going to best for you? If you want to compare, this 15×70 vs 25×70 guide will help you take a look at spec of each side by side. This review will help you to make the best decision, for you.
If you want a quick summary of this article, this is it. All Celestron SkyMaster models are reputable, well designed and constructed water-resistant binoculars that will provide you with sharp views of the night sky. The difference between the 15×70’s and the 25×70’s is primarily the magnification as they both offer the same light gathering ability. The 15×70’s provide you with a larger field of view (to see more of the sky at any one time), focus distance, eye relief and are typically better for holding. However, if you are looking for a more focused view of the moon and planets, then the 25×70’s will be best. For the 25×70’s however, you may want to consider getting a Tripod.
What is to follow is a direct comparison and analysis of the two sets of binoculars. However, consider that the Skymaster Series are considered as some of the most premium yet affordable binoculars on the market. So, let’s take a look at the two options and what they provide:
Celestron SkyMaster 15×70 vs 25×70
A Comparison of The Specification
Above you can closely compare the specification of each model against one another. But you may know be wondering what some of, or all of this means. Let’s quickly break this down further.
All SkyMasters are built with Porro Prisms.These are an Optical Design which is considered a superior way to collect and utilize light to show images.
Porro prisms are renowned for providing greater depths of field and a wider field of view than the standard “Roof Prism” design.
Magnification and Light Gathering Ability
Let us know consider the strength of the binoculars. The 25×70 and 15×70 references the Magnification and the Diameter of the Objective Lenses (front lenses).
Those numbers are essential for us to understand what we can see, and in what level of detail when using them.
Magnification is shown against the power of the naked eye (so 25x/15x what your eyes will normally be able to see).
The Diameter (70) is the precise measurement of the lenses at the front of the binoculars (in millimeters).
So, ’25×70′ binoculars will provide 25 times the magnification on an image compared to your naked eye. It does this through lenses that are 70 millimeters in diameter.
15×70’s provide 15 times the magnification on an image compared to the naked eye. It does this through lenses that are 70 millimeters in diameter.
But what are the consequences of these subtle differences?
By now, you may be thinking that the higher magnification SkyMasters are superior as you will be able to see more. This is not always the case.
With any pair of Binoculars/Telescope, the higher the magnification provided, relative to the diameter of the lenses, the dimmer images will appear. You may not be able to see as much.
With Astronomy, the bigger the lenses you are using the better. Larger lenses can collect more light, and this means you can view fainter objects in the sky.
The front lenses are called ‘Objectives’ on binoculars, compared to the smaller lenses you look through (these are called the Eyepieces). Both lenses work synergistically to collect light from the sky (objects you are observing) and send it back to yours eyes. This allows us to see faint objects in the sky.
Taking these factors into consideration, choosing the right magnification in conjunction to the lens diameter of the objective lenses is very important. One is no good without the other.
Comparing the 25×70’s and the 15×70 SkyMasters, the former provides you with more magnification. This means you can essentially ‘zoom in further’. However because of this you will lose some of the “field of view” – how much of the sky you will see at any one time (to be discussed below). As both SkyMaster models have 70mm Objective Lenses, the sharpness of the images they provide will not differ between them because they can both gather the same amount of light. Therefore the decision will be how much do you want to see at any one time.
Angle of View
The Angle of View is the technical term for how much of the sky you can see at any one time. This is the measurement of the angle that appears when looking through the optics. It is expressed in °.
If you take a look at the specification table provided, the 15×70 SkyMasters give you a greater Angle of View (4.4°) compared to the 25×70 SkyMasters (2.7°)
So with the 15×70’s you will be able to observe more of the sky at any one time than if you were to use the 25×70’s for the same task.
Field of View
The Field of View refers to the width of the image that you will be able to see. This is related closely to the magnification of the binoculars. Usually, the higher the field of view the better, this is particularly important if you are observing objects in the sky that move.
The larger the field of view, the more time and room for error you will have. Basically, the object will appear through your lenses for longer.
However, as field of view increases, magnification decreases; you cannot have both at the same time. For this reason, astronomers tend to opt for higher fields of view, with less magnification (e.g. the 15×70’s are normally preferred).
The 15×70’s have a superior field of view to the 25×70’s.
Minimum Focus Distance
The Minimum Focus Distance is the shortest distance that a lens can focus at.
This will largely dictate your ability to observe finer details of planets, stars and other objects that you choose to view.
Minimum focus distance is also closely tied to Magnification, so as you will see the 25×70’s provide a higher minimum focus distance than the 15×70’s.
Exit Pupil Diameter
The Exit Pupil Diameter refers to the light that comes through the Eyepiece. Specifically it is the measurement of that light. This measurement is taken in millimeters – dividing the length of the objective lens by the magnification: Here is what it is for both models of the SkyMasters:
The larger the Exit Pupil Diameter, the better the binoculars will perform in low light conditions, especially in darkness (like during the night). This will help images to appear brighter.
The Exit Pupil of binoculars should be referenced against your own eye pupil dilation (once it has become dark-adapted). for the majority of people, eyes dilate to a range between 5 mm and 9 mm (the latter being the max dilation of a human eye).
Here is something to consider on the Exit Pupil Diameter. If the binoculars provide more than than the dilation of your eye – a lot of that light will be going to waste (it will fall onto your iris but is not able to be used by your eye).
Taking all of this into consideration, the 15×70 SkyMasters will provide more light into your eye and you should be able to see more with them. They are particularly useful in darker conditions.
Eye relief is just the distance that your eyes will be from the eyepieces (when the maximum field of view can be comfortably observed). This is measured in millimeters.
The measurement is the spacing in between the eyepiece lens and the area behind the eyepiece (where light is focused to create views of the image).
With Eye Relief, anything under 10 mm will be largely uncomfortable which is why the SkyMasters provide more than this. The higher the Eye Relief, the more comfortable the Binoculars will feel. If you wear glasses, you are going to want this to be as high as possible as you will need the extra distance.
The 15×70’s provide a higher eye relief than the 25×70’s and will therefore be more comfortable to use.
Every pair of binoculars in the SkyMaster range are designed with a Center Focus.
This means you will have a single and central wheel to help you focus in and out of objects in the sky. This wheel will give you flexible views of the sky, and you can quickly and easily change focus.
This makes them more versatile and adaptable than other focus types.
This is just how heavy the binoculars are (and how much you will need to hold).
This is something to consider depending on when and how you will use them. Do you want to observe the sky for long stretches of time, what are your personal preferences and what is going to be possible and most comfortable.
The 15×70’s are lighter by 0.25 lbs, despite having the same dimensions in terms of size: 220mm x 110mm x 280mm (8.7″ x 4.3″ x 11.0″).
This makes the 15×70 better suited for carry and holding for longer periods of time without discomfort.
However, both pairs have a Tripod Adapter included. This means that you can attach them to any Tripod (three-legged base). This may or may not be appropriate for you but it does make observing easier, less tiring and also helps you to focus more steadily.
Verdict and Final Words
In this SkyMaster 15×70 vs 25×70 comparison, we’ve taken a look at a lot of specification and differences between the pairs.
At the end of the day whilst both pairs are good, you need to consider what, when and how you will be using them.
Do you want to more closely observe planets and their detail? If so, the 25×70’s may be for you (for the extra magnification).
However, depending on your maximum budget/your preference for a lighter pair or for the larger Field of View, you may opt for the 15×70’s.
Ultimately, both pairs have very high and positive reviews and recommendations on Amazon. Whether its the 15×70’s or the 25×70’s, the Celestron SkyMasters will provide you with great, crisp and clear views of the night sky.