Dobsonian vs Cassegrain – Which to choose?

The Dobsonian is one type of mount, while the Schmidt-Cassegrain and the Newtonian are different configurations of the optics inside the telescope. The Dobsonian is one type of mount, while the Schmidt-Cassegrain and Newtonian are different configurations of the optics inside the telescope.

Personally, I and many others would recommend investing in a Dobsonian reflector first because of its value, but SCTs, with their lower maintenance, might change your mind. In recent years, Dobsonian telescopes have become one of the most widely used and purchased telescope variants, and you can find a good telescope for $500.

The SCT will be more compact and easier to move and mount and the dob will probably have a wider field of view. However, they tend to be much more expensive. Dobsonians and Cassegrains are the two main types of reflecting telescopes. However, their operation is very different from that of a Dobsonian.

Dobsonian vs Cassegrain

Dobsonians and reflecting telescopes in general tend to have a short focal length, while Cassegrain telescopes have a long focal length. The secondary mirrors are about the same size (Orion shows that the XT10’s secondary is 63 mm, their classic Cassegrain GSO is 68 mm).

Perhaps the most prominent feature of a Dobsonian is its Altazimuth (sometimes referred to as Alt-Az) mount. The big difference is the FOV, which differs to other types of telescope. Many of the large telescopes used by NASA and other space agencies are Dobsonian telescopes, including the Hubble Space Telescope.

However, it is important to note that some Cassegrains fall into the category of Catedioptric because they use a slightly different optical system (it is basically the combination of refraction and reflection optical systems). Dobsonians are generally the best choice for beginners because of their ease of use and lower cost. The Cassegrain assembly will be lighter if mounted individually. Dobsonian mounted telescopes are almost always Newtonian due to the ideal eyepiece placement.

Dobsonians will be heavier by individual pieces. Image Brightness – In my experience, you are going to get brighter images with more of a ‘pop’ with a Dobsonian telescope. An alternative to Dobsonian telescopes are Cassegrain telescopes (another type of reflecting telescope option). But I’m a fan of the cassegrain too, so if you get a good one WITH A GOOD MOUNT, then you’ll definitely go for it.

If you are going to get a Go-To dob then the differences are a little less since most dobs are manual. It depends a lot on the type of sky you have where you will be seeing most of the time and your interest in planets vs DSO’s, I might buy the SCT for planets and the dob for DSO’s.

On the other hand, the Cassegrain telescopes provide the same power and performance (aperture), but have a more compact design. The 10″ dob on the other hand will have a significantly wider FOV so you can see more ratios.

In my experience and research prior to buying my own scope, Dobsonian scopes tend to provide brighter images. That Cassegrain has a really long focal length, so it won’t show you the wider FOV of some larger DSO.


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It also features Orion’s CorrecTension spring system to aid balance and secure attachment to the base. A large primary mirror at the bottom of the tube collects light and focuses it onto a small secondary mirror, which deflects the light cone down the side of the tube and into the eyepiece.

You can change various types of eyepieces for magnification and field of view depending on your needs, as you are not limited by size. Besides the size of the mirror and the weight of the telescope, there are other things to consider when buying a Dobsonian telescope.


While Dobsonian telescopes are not always super lightweight, portability and transportability are still pretty good. He has found refractor and reflector telescopes, but he has also discovered that a Dobsonian telescope exists.

The larger Dobs, while bulkier to transport, are very popular with experienced observers, thanks to their enormous light gathering capacity and, again, their affordability compared to refractors or catadioptric telescopes. Zhumell has a great reputation for good quality Dobsonian telescopes, and the entire Z series is noted for its attention to detail and quality.

Because Dobsonians are designed with a short rocker box base rather than a tripod, a smaller, portable Dobsonian telescope is much easier to look through when sitting on a table or other elevated, flat surface. You can pack this baby up and transport it across the country if that’s where you can get the best views – no problems there.

Instead of adjustable tripods and sophisticated mounting technology, Dobsonian telescopes are spartan by comparison. Product image color is for reference only, actual product color may vary depending on dealer).

Yes, Dobsonian type telescopes can be used for short exposure astrophotography, especially for planets and the Moon. If you are looking for pure visual performance on a budget, a hand-held Dobsonian telescope is your best choice. Even relative to similar aperture Newtonians in equatorial mounts, Dobsonians are delightfully inexpensive.

There’s a lot to see with this Dob, and with 203mm aperture, you can take advantage of dark skies to access the thousands of DSOs waiting to be explored.

Its affordability and simplicity of operation make the Dobsonian a great first telescope to get started in the amateur astronomy hobby, especially those in the 6 to 8 aperture range. It is responsible for reflecting the light collected by the primary mirror through the focuser and eyepiece to the eye.

A Dobsonian with truss tube increases the portability of large Dobs by using truss poles in the central part of the telescope tube assembly. Zhumell’s “tabletop Dobsonian scope” offers a revolutionary balance of flexibility and affordability, without sacrificing too much power.

The folding feature consists of rods that retract and extend into place, so you don’t have to deal with removing any rods and parts. The bearings are small and can be replaced with larger ones to provide ultra-smooth movement.

Focal Length

A key consideration in a Dobsonian telescope is the focal length (or focal length, which is the same thing). It’s not an easy telescope to carry and mount alone, but even so, observers have carried telescope systems of nearly and over 100 pounds before – something to think about in context.

As for the mount, it has a carrying handle on the base that is very convenient for travel, and it is relatively light at 21 pounds (approx. For a beginner looking for a telescope with great visual performance and versatility, the Dobsonian is hard to beat.

A good example of this Dobsonian telescope design is the Explore Scientific Truss Tube Dobsonian Telescope in an aperture of 10. However, you will have to purchase more accessories for the telescope as it only comes with a low power eyepiece, a 25mm.

The Dobsonian mount telescope is popular with amateur astronomers and telescope makers because of its simplicity. Secondly, most Dobsonians are fully manual, which means that they do not usually have computers or motorization to aim the targets for you automatically.

In reality, and taking a look at the specs, the 8 is just as portable as the model 6, so you don’t lose any convenience advantage by switching to the larger size. The larger mirror, located at the rear of the tube and responsible for light gathering, is called the primary, and the smaller mirror, located higher up, is called the secondary.

Dobsonians can provide fantastic views of both deep sky objects and solar system objects such as the planets and the moon. Below is a list of the most common Dobsonian telescope apertures and how they compare to each other in terms of light gathering ability.


Catadioptric Cassegrain telescopes use two mirrors, often with a spherical primary mirror to reduce cost, combined with one or more refraction-correcting elements to correct the resulting aberrations. Since Cassegrain telescopes use two mirrors to focus the image, many Cassegrain designs such as the Ritchey-Chretiéns are reflecting telescopes.

In the late 1920s, Ritchey and Chrétien recognized that the cause of coma in the classical Cassegrain is that the final U′ of the marginal beam is too small, making the marginal focal length F′ too long. With a Cassegrain configuration, it is not necessary to route the signals along a beam, leading to somewhat less cable loss.

The value of the Cassegrain reflector was not fully appreciated until a century later, when English optician Jesse Ramsden discovered that this design reduces image blurring caused by the sphericity of lenses or mirrors. A cassegrain telescope is a general term used to describe a telescope design that uses a convex primary mirror and a concave secondary mirror.


Cassegrain reflector, in astronomical telescopy, is an arrangement of mirrors to focus incoming light at a point near the main light-gathering mirror. Although less common, telescopes such as the classical Cassegrain and the (uncorrected) Dall-Kirkham designs are excellent reflectors used primarily for high-level planetary observing and imaging.

If one changes these conditions to a smaller field, of the order of 1° diameter, and Cassegrain focal ratios ≈ 10, then one finds a family of aplanatic SC designs with σ ≈ 1 and tolerable astigmatism. This is what is known as folded optics in the telescope world, and allows for a very long focal length design in a compact body.

With a different secondary than the one designed for the Cassegrain focus, the focus of the telescope is usually located in a different physical position. This last statement is true for antennas whose diameters are large compared to the wavelength of the signal being received (on the order of 40 wavelengths); smaller antennas tend to suffer too much diffraction at the edges of the sub-reflector for the Cassegrain antenna to be useful.

Select the Cassegrain telescope that suits your specific observing needs, as not all offer the same features. The Cassegrain reflector is a combination of a concave primary mirror and a convex secondary mirror, often used in optical telescopes and radio antennas,. Learn more about Cassegrain telescopesCassegrain (or catadioptric) telescopes offer versatility and high magnification power. Selecting additional accessories, such as telescope diagonals and prisms, can give you a clearer planetary view and increase detail.

Maksutov-Cassegrain options offer compact sizes and reliable optics for people living in the city, and are designed primarily for viewing larger planets and double stars. Orion Telescopes offers both Schmidt-cassegrain and Maksutov-cassegrain telescopes in a variety of sizes, all of which provide excellent image quality and full viewing capability.

To take advantage of the design flexibility of Cassegrain telescopes, many are fitted with interchangeable secondaries and each primary-secondary combination offers a different focal length and telescope focal ratio. Light enters at the front of the tube and passes to the bottom, where it reflects off the primary mirror, back up to the secondary mirror, and finally back down the rear of the telescope to the focal plane.

SCT telescopes produce better results in open spaces because city lights can cause glare and poor viewing conditions. This design places the focal point in a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system.

The Cassegrain reflector is a combination of a concave primary mirror and a convex secondary mirror, often used in optical telescopes and radio antennas, whose main feature is that the optical path folds back on itself, relative to the entrance aperture of the primary mirror of the optical system. The Cassegrain system is somewhat more difficult to align, as the installer must align not only the feeder but also the sub-reflector.

Thus, the classic Cassegrain has an ideal focus for the main beam (the center point diagram is a dot). The Schmidt-Cassegrain was developed from the wide field Schmidt camera, although the Cassegrain configuration gives a much narrower field of view.

However, since most Cassegrain telescopes have very long focal lengths, it can be like looking at space through a coffee straw. Small Maksutov-Cassegrain telescopes are excellent for carrying, while Schmidt-Cassegrain telescopes accept a wide variety of accessories for both observing and astrophotography.

Schmidt cassegrain and other Cassegrain types

Maksutov-Cassegrain telescopes are similar to Schmidt-Cassegrain telescopes in that they use both mirrors and a lens to focus light onto a smaller area. The Schmidt-Cassegrain is a type of catadioptric telescope with a folded light path that uses both mirrors and a lens to focus the light onto the focal plane.

Schmidt-Cassegrain telescopes come in many different sizes and configurations, so it is a good idea to narrow down what you are looking for first. Variations of the Schmidt-Cassegrain design include Celestron’s EdgeHD and Meade’s Advanced Coma Free (ACF) optical systems.

As a result, the SCT telescope tube is shorter than other designs of the same aperture, making it easier to transport, store and attach to your choice of mount. The Schmidt-Cassegrain is a catadioptric telescope that combines the optical path of a Cassegrain reflector with a Schmidt corrector plate to make a compact.

Finally, because Schmidt-Cassegrain telescopes are so popular, there are plenty of accessories available that will allow you to do visual astronomy as well as multiple types of photography with everything from your smartphone or point-and-shoot camera to a DSLR or dedicated astronomy camera.

Whether you are buying your first telescope or are an advanced astrophotographer, OPT has a wide selection of schmidt cassegrain Telescopes for any application.

Reflecting SCT

Refractors have the disadvantage of being the most expensive per unit aperture, so refractors tend to be smaller than all other designs. The market for commercially produced Schmidt-Cassegrains has been dominated by Celestron and Meade Instruments Corporation since the 1980s.

Refractor telescopes have the advantage of having an unobstructed light path, which produces greater visual contrast than other optical designs. This includes lunar and planetary observation, astrophotography and deep space observation, provided they have a large enough aperture.

Schmidt-Cassegrain telescopes are some of the most popular telescopes on the market, favored for their large aperture in a relatively small and lightweight package. Schmidt-Cassegrain telescopes are high-end multi-purpose telescopes, ideal for observing the moon, planets and deep sky objects.

These telescopes are named after their designer, John Dobson, who sought to build a low-cost large-aperture telescope. A Dobsonian telescope is a Newtonian reflector mounted on a simple but stable alt-azimuth (lazy Susan style) mount.

The disadvantage is that the images they produce are inverted, which means they are not suitable for earth observation. Refractors or refracting telescopes are a design that uses only lenses to focus light; any other type of telescope relies on one or more mirrors to perform that task.

Perhaps the best way to describe a Schmidt-Cassegrain would be to label it the jack of all trades among telescope designs. Celestron’s design, known as EdgeHD, incorporates a group of coma correction lenses into a standard Schmidt-Cassegrain.

Schmidt-Cassegrains equipped with a 90-degree stellar diagonal produce a vertical but inverted right-to-left image, making them suitable for ground-based observing as well. The main advantage of a Schmidt-Cassegrain telescope is that it usually offers the highest degree of portability per unit aperture.

The Schmidt-Cassegrain is a catadioptric telescope that combines the optical path of a Cassegrain reflector with a Schmidt corrector plate to make a compact astronomical instrument using simple spherical surfaces. Schmidt’s Cassegrains are at the high end of the scale, so incredible views are obtained with all models.

Both companies now offer more expensive derivatives of the Schmidt-Cassegrain design that are technically known as flattened Schmidt-Cassegrains. We believe that most users of visual-only telescopes will be satisfied with the original Schmidt-Cassegrain designs. Schmidt-Cassegrain telescopes use mirrors and a lens (corrector plate) to focus light onto a smaller area.

The SCT has an optical tube that is much more compact and portable than a reflector or refractor of the same aperture, and there is a large selection of accessories available that are designed specifically for the Schmidt-Cassegrain.

The light path of a Schmidt-Cassegrain is folded, which means that the light has a couple of bounces before it reaches the eye. Both the Schmidt-Cassegrain and the Maksutov Cassegrains are part of the catadioptric or compound type of telescopes, with very similar advantages and disadvantages.

The Schmidt-Cassegrain telescope is worth a closer look, whether you want to do visual astronomy, earth observation or photography of day or night objects. The SCT telescope has a primary and a secondary mirror, but also uses a very thin lens called a corrector plate to enhance the image.


Newtonian reflecting telescopes are an optical design that uses a mirror to focus light onto a smaller area. The long, thin optical tube of a refractor is the image most people associate with a telescope. They are moderately well suited to a wide variety of applications, such as lunar, planetary, deep space, and even terrestrial observation.

Some telescope designs use mirrors to collect and focus light (Newtonian reflectors) and others use lenses (refractors), but catadioptric telescopes use a combination of mirrors and lenses to do the job.

It is less expensive to produce a mirror than a lens, and that advantage increases with the size of the telescope. Dobsonian telescopes may seem unconventional to the first-time buyer, but the fact is that they dominate the market for amateur telescopes over eleven inches in aperture.