How To Set Up A Dobsonian Telescope

What is a Dobsonian Telescope? A backyard astronomer's best friend

Terminal Updated: 25 September 2022

Dobsonian telescopes are a type of reflecting telescope that is very popular in the visual astronomy community. They piece of work by reflecting the light travelling inside their optical tube assembly (OTA) from a curved primary mirror to a flat secondary mirror which so directs the light to the focuser. What makes those telescopes "Dobsonian" is the fact that they are mounted on a simple altazimuth mount.

This telescope design was created by John Dobson in 1965, who wanted to make apprentice astronomy accessible to a larger number of people. He nicknamed his project "the sidewalk telescope" considering he used to have his Dobsonian telescope through the streets of San Francisco and let bypassers look at the night sky through the eyepiece.

dobsonian telescope

How do they work?
What type of mount do they utilise?
Advantages
Drawbacks
What tin can you observe?
Maintenance tips
How much do they toll?
Where to purchase a Dobsonian telescope?
Edifice a homemade Dobsonian
Upgrading your telescope

How practice they piece of work?

When you point a Dobsonian telescope at a celestial target, it collects lite rays from that object through the aperture (the opening). This light travels inside the telescope'south optical tube assembly and hits the parabolic mirror placed at the end of the tube. The light then bounces off the chief mirror and is directed towards the apartment secondary mirror. It bounces off the secondary mirror again and is sent to the focuser where you place your eyepiece.

For this to work perfectly, your telescope must be properly collimated. This ways aligning the chief mirror so that the light bouncing off it is perfectly directed toward the secondary mirror without any loss of light rays.

And that's it! It'southward a very uncomplicated telescope to use. They are nicknamed "Lite Buckets" because their wide opening makes their light-gathering adequacy i of the best on the market place. As long as you are fine with having to manually find and rails your telescopic targets yourself, a Dobsonian telescope is without a doubt the best choice for getting started with visual astronomy. Regarding accessories, you should experiment with eyepieces and Barlow lenses to encounter what works all-time based on what you observe.

What type of mount do they use?

The Dobsonians are mounted on an altazimuth platform. To point your OTA towards your chosen target in the sky, you lot volition beginning take to manually orient the telescope to the correct or left by gently pushing the azimuth turntable. And so you will need to adjust the altitude axis by turning the control knob on the side of the rocker box, which allows you lot to move the optical tube up or down. Once you have your desired target in the middle of the eyepiece, you tin tighten the control knob to concord the tube in place.

Dobsonian mounts are indeed very simple in design and easy to manufacture, which is function of the reason why they are then affordable. They are quite robust too which is particularly important when using large aperture telescopes.

When placing the Dobsonian mount on your observing spot, brand sure that the base is properly levelled on the basis. Some astronomers also place the mount on a vibration pad which significantly reduces vibrations effectually the telescope and makes for a ameliorate viewing experience.

The advantages of using a Dobsonian telescope

They have big apertures

Dobsonian telescopes are renowned for offering the widest aperture at the best price. The discontinuity is the size of the opening of the telescope where the light enters the OTA (optical tube assembly). The larger the discontinuity = the telescope collects more calorie-free = the observed image is brighter and sharper. They are therefore popular for visual astronomy: the planets, the moon and some deep-sky objects are swell celestial targets for this type of reflecting telescope. Dobsonians are particularly suitable for big openings (6 inches upwards to 36 inches) because they utilize mirrors instead of drinking glass, which means they are cheaper to manufacture than refractors (doublet & triplet) and Schmidt-Cassegrains.

They are great for planetary observation

Dobsonians are among the best planetary telescopes bachelor to purchase with a low upkeep. Their large discontinuity allows them to collect lots of low-cal reflecting off the planets, significant that yous may bask a much brighter and clearer prototype within the eyepiece. Jupiter and Saturn are amidst the most popular targets, as Dobsonians can easily resolve the peachy cerise spot and Saturn's ring. Their large aperture means that Dobsonians are more than sensitive to atmospheric turbulence, so a steady "seeing" is very important when observing the planets. If the weather condition is on your side, be prepared to be wowed at the view of the giant planets and their moons.

They are like shooting fish in a barrel to use

Dobsonians are amidst the easiest and quickest telescopes to set up. You just demand to identify them on the ascertainment spot, check that they are well collimated, select your eyepiece, locate your target with the help of a stargazing mobile app, point the telescope at it, and yous're ready to go! They don't require whatever cables to connect to a computer, whatsoever ability source for the mount, whatsoever polar alignment, or any complex software setup. For these reasons, they are particularly popular at star parties and are a prime choice as a first telescope for beginners.

The eyepiece is besides ideally placed, at the top of the OTA which ways you lot don't accept to bend down too much to observe the starry sky.

Lower cost compared to other types of telescope

As we mentioned before, reflectors are less expensive than a refractor or a Catadioptric telescope. They are perfect for beginners considering they offer the about ability for the least amount of money . This is due to the fact that they are non costly to manufacture… The mount is mostly made of wood, and the OTA uses mirrors rather than high-grade glass lenses with a special blanket. It is hard to not be tempted by a total astronomy kit that includes: a powerful telescope, a solid mount, and a set of high-quality eyepieces, and sometimes a moon filter for about 350 dollars.

They do not endure from image baloney

To enjoy a sharp view of your target in your eyepiece, you desire all the low-cal nerveless through the aperture to be focused at the same point and at the same time. Some telescopes that collect light through a lens, for instance, suffer from what is known as chromatic aberration. This is when the different coloured light rays (ruddy, blue, green) are not focused on exactly the same place, causing colour fringes in the image. For example, Jupiter may appear to take a subtle but distinct ruby-red and blue hue on its sides.

Because Dobsonian uses mirrors to reflect light, each wavelength of the spectrum hits exactly the same signal at the same time.

The cons of using a Dobsonian telescope

Big Size

Although an 8 or ten inch Dobsonian telescope can be carried by one person, information technology is not actually a "grab and go" type telescope. If you lot want to go to a night sky surface area, yous volition need sufficient space in your car. Besides, if y'all've had a long day, you may not be motivated to lift 45 pounds worth of equipment from your storage space to your backyard. Consider this fact before you buy a Dobsonian, as you probably don't want to invest in a telescope that volition only exist used a few times a year.

Harder to store

Earlier buying a Dobsonian scope, yous demand to determine if y'all take plenty room to store it in your home or backyard shed. Dobsonian telescopes are quite large and take up a fleck of space. Due to their optical design, their aperture is actually quite wide and open, which makes it easy for dust and moisture to attain the mirrors. It is therefore important not but to find a space big enough to store them simply also to brand sure that the place is acceptable for a high-quality astronomical telescope.

They are not suitable for astrophotography

You won't exist able to see every single object from the Messier Itemize. Unfortunately, because archetype Dobsonians use an Alt-Azimuth mount, they are non suitable for taking images of deep-sky objects. They are lacking one of the most important factors for astrophotography: a tracking mount that allows you lot to accept long exposure pictures with your DSLR. A motorised equatorial is paramount for astrophotography equally it counters the Earth's rotation. Without it, your images would be full of star trails.

If you are interested in taking photos of deep-heaven objects, you should await into getting a Newtonian or a Refracting telescope and a motorised equatorial mountain instead.

What can you observe with a Dobsonian Telescope?

You lot can hands observe the almost interesting planets such every bit Venus, Mars, Jupiter and Saturn. Dobsonians are sometimes chosen "planet busters" every bit they have the perfect telescope features for observing them: large aperture and long focal length . Adding a Barlow lens can really increment the magnification power of the telescope and improve your viewing experience.

Venus : You volition be able to observe the different phases the planet is going through.

Mars : Yous will encounter the distinct carmine colours as well as the polar ice caps.

Jupiter : You volition appreciate the different colours in Jupiter'south belts, the large cherry-red spot too as the Galilean moons (Io, Europa, Ganymede and Callisto).

Saturn : You should hands resolve the shape of the planet, some color differentiation, Saturn's band including the Cassini division. On a clear night with a stable atmosphere, you may even be able to detect Saturn'due south principal moons: Titan, Rhea, Dione, Tethys, Enceladus and Mimas.

I accept never tried to observe the most distant planets (Neptune and Uranus) considering they are too far away and would probably wait similar a bluish ball of calorie-free.

Dobsonians can give you access to many of the brightest deep-heaven objects (galaxies, nebulae and star clusters), such as the Pleiades, Orion and Andromeda. These deep space targets can only be visually observed since it is very difficult to practise any Astro imaging with this type of telescope.

How to care for your Dobsonian telescope

Telescopes are an important investment. There is no other way to draw information technology. Whether y'all accept a big or modest budget… when you spend a few hundred dollars on a single piece of equipment, you desire it to last. Although Dobsonians are durable and crave niggling maintenance, we have a few recommendations that volition help you protect them and brand them terminal longer.

Some archetype Dobsonians bases are fabricated of particle forest glued together (like some Ikea furniture) which makes them particularly vulnerable to moisture and causes them to curve and warp slowly over time. Avoid placing your Dobsonian mount on wet or snowy grass. Some users have built an elevated wooden platform for the scope to sit on during their stargazing sessions.
Store your OTA within a large travel bag. This ensures that your tube is protected from wet in the storage expanse, from whatsoever insects deciding to live in your telescope and from any dust reaching your primary mirror.
Due to the temperature difference between the outside and inside, some dew may course inside your telescope once you bring it home. Practice not put the grit cap on for nigh half an hour to allow the dew to misemploy. Point the telescope down while y'all let it defog to prevent dust from entering.
Dobsonians crave regular collimation because the primary mirror might move a little when you move the telescope in and out of the firm. Collimating your telescope is the act of realigning the primary mirror by adjusting the three small rotating knobs at the back of the telescope. This ensures that the collected lite is fully directed toward the secondary mirror then that you don't lose any "data".

How much does a Dobsonian telescope costs?

fifty to 250 dollars: Tabletop Dobsonians are a smaller version of the classical Dobsonian. Brand no mistake, they may await like children'southward telescopes, but they are much more powerful. They are perfect for the space lover who merely wants to enjoy the night sky every at present and again without getting into astronomy too seriously.

250 to 500 dollars: This is the ideal price range for those who want to become a little more serious nigh visual astronomy. Dobsonians with a 6 or 8-inch aperture are the best introductory telescopes as they offer the best value for the money for beginners.

500 to g Dollars: At this price point, Dobsonian telescopes get very large, x or 12 inch in aperture size. This is usually the upgrade that experienced astronomers get for, should they decide to stay in the visual astronomy field rather than astrophotography.

1000 to 2500 dollars: If you are wanting la creme de la creme of Dobsonians. At this level, your telescope will come up with a super large aperture (xiv" to 16"). They volition be equipped with fantastic features such as the collapsible FlexTube design and SynScan computerised Get-To applied science.

Related: Our beginner'due south guide on how to purchase a telescope.

Where tin can you buy a Dobsonian?

As they are relatively affordable, I recommend that you buy a brand new Dobsonian rather than a used ane on eBay or gumtree. This way, you can be sure that the equipment is delivered in impeccable condition and under warranty.

If you are ownership a telescope for the get-go fourth dimension, I suggest yous visit your nearest astronomy shop. There, you volition be able to talk to an experienced astronomer who can explicate to you how Dobsonian works, what information technology can and cannot practice. They are very helpful and happy to share their passion for telescopes and astronomy in general.

If you don't have admission to an astronomy shop, there are a number of online shops where you tin browse and choose a Dobsonian :

Online Uk Stores

https://www.harrisontelescopes.co.uk/
https://uk.telescope.com/
https://www.telescopehouse.com/
https://www.tringastro.co.uk/

Online Usa Stores

https://world wide web.highpointscientific.com/
https://www.telescope.com/
https://optcorp.com/
https://telescopes.net/

Among the brands you want to check out, Apertura (in item the Apertura AD8 model) has a reputation for building superb Dobsonian telescopes at a bang-up price. Other reputable brands include Sky-Watcher, Orion, Meade and Zhumell.

Notation: Some telescope manufacturers are known to increase their prices when need is high. Have the time to research the telescope you are interested in. There are tons of online resources, such as forums where you can get advice.

Building Your Own Dobsonian

The design of this classic telescope is so simple that many people have managed to build their own homemade Dobsonian using basic materials such equally plywood, wood and metal fasteners. The most important function of the project, as well as the most expensive, are the primary parabolic mirror, the secondary flat mirror and the focuser. It is essential to summate exactly how far the secondary mirror must exist placed from the master mirror in lodge to reach focus. In that location are many videos describing the process from beginning to terminate:

How to Brand a Telescope – 8 Inch Newtonian Reflector (Role 1)
How to Make a Telescope (Role 2)

If y'all ever built your own Dobsonian, allow u.s.a. know in the annotate, we would love to characteristic your images!

Upgrading your telescope

Similar any other astronomer with a passion for this fascinating hobby, there volition come up a time when you volition master your Dobsonian telescope perfectly. You lot volition have used information technology to its full potential and will be looking for ways to get more ability out of it. It volition be time to upgrade it! The usual next step for a visual astronomer would exist to start experimenting with astrophotography. Fortunately for you, in that location are many excellent Newtonian telescopes that are perfect for imaging objects in deep space. So you won't be lost, considering the optical design is the same equally your onetime Dobsonian.

If you are perfectly happy with observing planets , the moon and some DSOs, then your telescope upgrade would simply exist a Dobsonian with a larger aperture or one with more than advanced features similar a collapsible optical tube or even a GoTo functionality. Since Dobsonians are a popular type of telescope, y'all should accept no problem selling your faithful telescope on the dissimilar online marketplaces.

Practise you own a Dobsonian telescope? We'd love to hear your experience with it in the comment section!

Tom Urbain

Hey! I'thou Tom Urbain, the founder of StarLust.org. I have been obsessed with space from a very young historic period. When I'm not binge-watching space documentaries, movies or TV shows, I can exist establish in my lawn, carefully collimating my telescope… ready to discover the universe!

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