If you're reading this, then I'm assuming that you'd be interested in picking up one of Celestron's most popular telescope lines, which is the Celestron NexStar computerised Schmidt Cassegrain.
Now, the NexStar range comes in at a variety of different price points, starting at £504.99 for the 4SE, and finishing at £1,499 for the 8SE.
For the most part, this article will be relevant for the entire range (4SE, 5SE, 6SE, and 8SE), but seeing as I've recommended a few other telescopes specifically for beginners, I'm going to be objectively reviewing the 8SE in particular, which is the most common option, and in my opinion, the one that I would advise people to consider purchasing.
So without any further or do, let's jump straight into the fundamentals of the telescope, as they should ultimately dictate whether or not you should consider buying the telescope.
Aperture - 8 inch (203.2 mm)
Focal length - 80 inch (2032 mm)
F-ratio - 10
Maximum useful magnification - 480x
Assembly weight - 33lbs (15kg)
What does any of that actually mean?
Let's talk about it.
Starting with Aperture, the NexStar 8SE has an aperture of 203mm, or 8inches. If you're not already aware, the aperture of a telescope, or any mirror in fact, is simply a fancy word for its diameter. In other words, the diameter of the primary mirror is 8 inches.
This, along with focal length, is what ultimately differentiates the 4SE, 5SE, 6SE, and 8SE from each other. The higher the aperture, the more light the telescope can collect, and hence the clearer the image that you can obtain. Naturally though, the higher the aperture, the more expensive the telescope becomes to manufacture and sell.
While this isn't strictly true if you're comparing two different types of telescopes, the NexStar range are all fundamentally the same design, and hence the most important factor that you need to consider when looking these telescopes, is what you actually intend to see through the telescope...
Even with the cheapest option, the 4SE, with an aperture of 4 inches, you'll be able to identify Mercury, Venus, Mars, Jupiter and even Saturn without a problem. However, the clarity of the image will largely depend on the aperture of the primary mirror.
At 4 inches in diameter, you can expect to be able to make out the 4 Galilean moons of Jupiter (Europa, Io, Ganymede, and Callisto), the craters on the Moon, and, depending on seeing conditions, the rings of Saturn - for £504.99, you really can't complain with that, and if that's all that that you'd like to be able to see, then I'd definitely recommend going for either the 4SE or the 5SE.
However, if you're after something a bit more powerful, then your eyes should definitely be set on either the 6SE or the 8SE, and to be honest, at this price range, you're probably best looking at either the 8SE, or a completely different type of telescope that tailors your needs a bit better.
At 8 inches, you can expect to clearly identify the rings of Saturn, the polar ice-caps on Mars, the Great Red Spot on Jupiter, as well as it's different bands of colour, and you should also be able to identify the 2 outermost planets - Uranus, and Neptune.
Notice how I said "identify" though, as even at 8 inches in diameter, don't forget that Neptune is approximately 4 billion kilometers away... and the light that it receives, let alone is able to reflect, from the Sun is absolutely tiny. Hence, both the planets will mostly appear as blobs of colour in the average seeing conditions.
Just to talk more about that, it is extremely important that you consider your seeing conditions when looking at buying telescopes, and hence indirectly, its ability to be moved around (ie it's weight and "clunkiness"). You're ability to observe anything through a telescope will greatly depend on not only the specifications of that telescope, but briefly also:
How clear the sky is
How dark the sky is
How hot the telescope is (we'll talk more about that) and;
Wether or not you choose to use any filters (also more to follow on that)
The first 2 are pretty straight forward, as in the further away you can get from light sources, the brighter the night sky will appear, and hence the clearer the image that you'll be able to obtain, and passing clouds or haze will also obstruct and hinder the clarity of an image.
We'll talk about the last 2 at the end as it's more important that we cover the fundamentals first.
Okay, so this is where the design of the telescope comes into play.
The focal length of a telescope largely dictates the level of magnification that you can achieve. While this is also dependant on the aperture, for the most part, the aperture doesn't really vary all that much... As in, most amateur telescopes range between 4 and 12. The focal length of such telescopes, however, can be as low as 200 and as high as 3000.
Generally speaking, the higher the focal length, the higher the magnification that you can expect to achieve, and this is an extremely important factor that you need to consider, as it basically determines what you can and cannot see/image with the telescope.
What I mean by this, is that if you intend to be able to see planets such as Mars, Jupiter and Saturn fairly "close-up", then you absolutely need to be looking at a telescope with a high focal length. The NexStar 8SE has a focal length of 2000 mm, which you'll be glad to hear is ideal for such observations at this price level.
Observing the planets/the Sun/the Moon VS Observing Deep Space Objects
At 2000 mm, you'll be able to achieve an amazing level of planetary observation, with an exceptional level of quality that comes from an aperture of 8 inches.
This does, however, come with it's drawbacks... (Well it depends on what you're after....)
Something that you need to understand about telescopes is that, unfortunately, there is no "catch-all" kind of scope. I know that's a pain to hear, but it's something that is honestly extremely helpful to understand early on as it can prevent wasting money in the future.
Fundamentally, there's 2 types of observing:
Unfortunately, you can't have both in 1 telescope, unless you're willing to compromise on them by some factor of course. So if you're after something that's going to be ideal for observing the planets, then unfortunately it isn't going to be ideal for observing Deep Space Objects (commonly abbreviated as DSO), such as nebulae, galaxies, star clusters etc, and visa versa.
So, to summarise on focal length, the NexStar range in general is great for planetary/lunar/solar observation, but if you want to be able to do some deep space observation, you will at least need to go for the 8SE, although that does depend on what kind of results you'd be looking to expect.
Deep space observation is a completely different ball game from planetary observation, in that you need to consider so many other things which aren't really relevant to the NexStar range. Suffice to say though, that if you're looking to be able to get vibrant, colourful and clear images of galaxies or nebulae, I would advise looking at getting a small, mobile refractor and star-tracker as opposed to a Schmidt-cassegrain such as the NexStar range.
If, however, you mostly want to observe the planets, moons and the Sun*with an appropriate solar filter, and just want to dabble in galaxies and nebulae, then I'd absolutely recommend the NexStar range, but more specifically either the 6SE or the 8SE.
Following on well from the previous subject of observation, the focal-ratio of a telescope is essentially the relationship between its aperture and focal length, and it's one of the most important factors to consider if you plan on taking images with your equipment.
Just like how you can do different types of observation, you can also do different types of viewing:
They're both pretty self-explanatory, but if you plan on being able to take images of pretty much anything in the night-sky, then you definitely need to be looking at the focal ratio of the telescope that you plan on using.
F-ratio is determined by diving the focal length of the telescope by the aperture, and it essentially describes how "fast" your optics are.
I know that might sound a bit confusing if you're new to optics in general (ie you've never been interested in cameras and the like), but believe me it's pretty simple...
The lower the f-ratio, the faster your telescope is at producing an image from the incident light, which means that the you're able to produce clearer images than telescopes with longer f-ratios for the same exposure time.
For telescopes, the scale goes like this:
An f-ratio of 2 is considered extremely fast, and an f-ratio of 12 is considered extremely slow.
What does this mean exactly?
Well, at lower f-ratios, you're able to produce brighter images over a shorter period of time, which is ideal for people who are looking to spend hours outside collecting images and eventually stacking them together using the appropriate software to produce an insanely detailed image.
Personally, I've never really been interested in that, as the reason why I found observing the night sky so incredible is because I'm looking at a live image... If you feel the same way, then you can forget about the whole stacking game as well, and simply work with exposure times of 1-2 minutes or so, which you really do not need a low f-ratio for!
A high f-ratio means that you just need to allow your telescope more time to collect light, but when we're working with a few minutes at most, it really doesn't matter.
Something else to consider as well, is that our eyes don't operate like camera lenses, in that we can't increase our exposure time!
Therefore, since lower f-ratio telescopes are collecting light a lot faster than high f-ratio telescopes, images appear much brighter when observing with your eyes in lower f-ratio telescopes.
Essentially, this makes them amazing for dim objects like nebulae and galaxies, but horrible for already extremely bright objects like planets. Hence why high f-ratio telescopes like the NexStar line up are ideal for planets, but not so great for DSO....
The f-ratios of all the telescopes in the NexStar range are all pretty much the same, as remember it's the relationship between the aperture and focal length, so as long as you modify them both by the same proportion, you're f-ratio will remain the same.
They have an f-ratio of 10, which is for sure on the slower end of the scale - I wouldn't let this put you off though, if you're not interested in sitting outside for hours collecting images of deep space objects (although a lot of people just leave their equipment running outside and just check in on it periodically, which isn't so bad I guess...)
You can however, invest in a small piece of equipment known as a focal reducer, which essentially reduces the focal length of the telescope and hence makes it faster at collecting light.
They're very easy to use, and are similar to just putting in an eyepiece to look through. I'd definitely recommend getting one if you plan on being able to take things just a bit further with imaging DSO.
At f/10, the telescope has no issue in handling the light of brighter objects like planets, but when you get to very dim DSO such as nebulae and distant galaxies, it really would be beneficial to reduce the focal length - plus you can simply remove it when viewing planets to retain the high-level magnification that comes with f/10.
While that does sound idyllic, and in a few situations it definitely is, focal reducers can be incredibly expensive depending on your scope and how much you need the focal length to be reduced by.
As a beginner, I'd probably advise that if you would like to obtain detailed images of nebulae and galaxies, you should look at investing in a <f/5 telescope.
The design of the NexStar range
As you might know by now if you've had a look at getting into visual astronomy before, there are several different types and variations of telescopes that have been invented over the years.
In particular, the NexStar range follows a Schmidt-cassegrain design, which naturally offers both advantages and disadvantages.
Going through specifics of the design probably isn't all that relevant, but the main takeaways are as follows:
It's a very compact design and weighs extremely little given the focal length and aperture when compared to the more common Newtonian reflectors.
The NexStar 8SE comes in at a 14kg which allows it to be easily transported around. Believe me, this might not seem like such an amazing thing, but when you get started and realise just how much observations are affect by light pollution, the ability to stick it in the boot of a car and drive 45 minutes or so away from bright lights is a game changer.
So what is the NexStar all about? Why is it so perfect for beginners who are mostly interested in planetary observation, and why do they sell so well?
Well the Optical Tube Assembly (OTA) comes with a goto mount and controller, which means that, after a very simple process, you can view and track virtually anything in the sky with a click of a button!
The mount and controller has built in technology that stores the location of thousands of objects in the sky as data. All you have to do is enter your date and time, and voila....
Well, it's not quite a simple as that, but it's really not that complicated either which makes it extremely appealing to beginners and intermediates alike.
Humans have been chartering the night sky in detail for hundreds of years, and since there's nothing really random about our solar system in terms of the motion of planets, moons etc, technology has allowed us to accurately predict the location of thousands of objects at any point in time.
However, there is one piece of information that your telescope will need to know in order to accurately do this, and it can be a bit intimidating to beginners, but trust me, not only is it not that difficult, it also becomes increasingly easy as you do it.
The process is known as Polar Alignment, and an accurate alignment is absolutely critical if you want the telescope to accurately track objects over long periods of time.
As you're probably aware, everything in the sky appears to move as the Earth rotates, but this movement isn't random.
You might know that the Sun rises in the West and sets in the East, but the truth is that this can be said for every celestial object in the sky, which is due to the anti-clockwise rotation of the Earth. Importantly though, the Earth doesn't just spin randomly, and in fact happens to spin at an angle that's nearly directly pointed at a bright star called Polaris, commonly referred to as the North Star.
We use this star to easily identify the North Celestial Pole, and all you have to do is point your telescope's polar scope towards this point to allow your mount to rotate the telescope in exactly the same direction and at exactly the same speed as the Earth.
After accurately polar aligning, you will be able to view objects and track them across the sky, completely automatically, which is a huge plus for the NexStar series.
While it might seem easy enough to pull out a map of the night sky and point your telescope towards a point of light, it can actually be quite difficult if either you're in a heavily light polluted area, or the object that you wish to see isn't visible with the naked eye... A GO-TO feature can be exceptionally handy, and it's probably the reason why this line-up is so popular.
Tracking the night sky is not only helpful for visual observation, but it also allows for imaging. Without tracking equipment, it's very hard to obtain clear images as you need to allow for exposures of over 30 seconds or so. In that time, without tracking equipment, everything in the night sky will have moved across the field of view, making it near enough impossible to take clear images.
As you'll quickly find out with a telescope that doesn't track, the Earth rotates extremely quickly (1000mph), and objects appear to move very quickly over the night sky - another massive plus of the NexStar range...
In summary, the NexStar range are absolute powerhouses of telescopes, and are exceptional pieces of equipment when observing objects within our solar system.
The NexStar 8SE is their flagship model, and will offer unparalleled views (for this price range) of both the Great Red Spot on Jupiter, and the rings of Saturn, while also allowing you to identify the 2 outer most planets, Uranus and Neptune.
They are, however, designed for planetary observations, and hence fall slightly short when trying to image DSO.
Having said that, at 8 inches of aperture, the NexStar 8SE will allow for some imaging of bright nebulae and galaxies under the right conditions and exposure times.
Ultimately, it's as close to a catch-all telescope as you're going to get!
Looking to get one for yourself, or a relative perhaps?
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