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Practicality of Dobsonian telescopes

Practicality of Dobsonian telescopes


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I've been using binocular for more than a decade for visual observation. I'm thinking of upgrading to a telescope. The Dob caught my attention due to its simplicity in setup and also cost effectiveness. I was thinking of going for 8" or 10" Dob.

What I have also observed is - If I'm going to use dob, I need to keep moving the OTA frequently to keep the focus. If I'm going to use the dob alone, it is not an issue. But my concern is when I want to show the celestial objects to others, I need to frequently move the OTA to keep the objects in focus. It may become tiring if there are many people waiting to watch.

Has anyone encountered similar situation with dob? What are your thoughts? Did you ever feel that you should have gone for go-to mount instead of Dob? Any suggestions please?


An 8 or 10 inch Newtonian telescope is principally a fine thing. Much telescope for little money.

A Dobson is a Newtonian telescope mounted on a rockerbox (see Alt/Az mount for a discussion). Consequences are: cheap, lightweight, trivial setup, your're either on your knees or on a chair, too seldom in between, it needs constant adjustment because the sky doesn't move that way.

If you want to track stars you need an equatorial mount, a cross of 2 axes of which one points to the celestial north (or south) pole. The same tube from the Dobson can also be mounted there. They can be motorized on one or both axes or/and have a computer built in to automagically find an object out of a database, then they are decorated with the "goto" attribute.

They are heavy, expensive (multiple times the price of a newton tube) and need a setup ritual each time they are moved. But once oriented, a motorized mount, connected to some software and computer, can be left alone for hours and will track the stars it points to.


So, the question is: do I want it light and cheap and don't I care about gymnastics, then the Dob. Do I want to go further and track things, do photography, than the other way. Perhaps with a sexy apochromatic refractor. But that's easily more than 20 times the price of a dob without camera stuff.

I personally don't do goto. Finding things is half of the fun for me. I go with equatorial mounts, a small portable one and one for photography setup I can drag outside. How about, you start with the Dob. If you bite, you're going to invest more anyway :-)

Edit: there is a third way (and potentially others) that might be worth considering, that would be a telescope like the one in this thread, a small reflector mounted on a computerized alt/az mount.


You are correct that a traditional dob will require frequent manual intervention to stop objects drifting out of view. There are 2 main to deal with this:

  1. keep to low magnification and use a wide angle eyepiece
  2. get a goto dob. These can be had for a reasonable price in many countries, particularly if you don't exceed 8" (200mm) aperture.

As @a_donda implies, you can see an awful lot with an 8" scope, especially if you have reasonably dark skies.


Cost effectiveness? That also means you get what you pay for.

When you compare a Dob to a similar sized Goto telescope the Goto cost seems to be extremely high.

When you compare the versatility of the two, the dob is so far behind it thinks it is first.

That will upset a few dedicated Dob users but many of them have only used a Dob. They have accepted the limitations of the dob and are willing to live with them. I refuse to allow tradition to limit my viewing.

What is your maximum budget? Every penny that you can beg borrow or steal?

If all you can possibly afford is a dob then that's all there is to it. If you can afford a goto (new or used) that is your best choice and will give you the most enjoyment out of the hobby for years to come.

The traditional eyepiece has limitations as well. I suggest you take a look at what people can see with the electronic eyepieces. An electronic eyepieces is just a very sensitive camera that is generally used for direct viewing on a small screen rather than for making photographic images.

I have used Mallincams for nearly fifteen years and viewed with eyepieces for over fifty years before that.

There are a lot of objects in the deep sky one can see with the newest technology. When I used eyepieces my viewing was basically limited to the Messier and Caldwell lists. I recently compiled a new list of 26761 deep sky objects that can be seen with a 10" SCT setup like mine.


A Guide to the Best Dobsonian Telescopes on the UK Market

So you finally made up your mind about getting a Dobsonian telescope? Well, you’re no doubt finding out just how many different models and types there are in the market. But before you get overwhelmed and make a hasty decision, we’ve chalked up this here buyer’s guide and some of the best telescopes already making rounds in the UK.

Looking for a balanced, powerful yet affordable dobsonian telescope with all the frills? Then look no further than the SkyLiner 200 P Parabolic Sky Watcher. This is the best overall Dobsonian that has some of the characteristics of a high end model without the unbelievably high price.

How about a state of the art, fully computerized dobsonian telescope to give you a huge head start? The Orion SkyQuest XT8i Dobsonian IntelliScope is the smart solution for the tech loving astronomer willing to make a solid investment.

So you love peering into the great expanse of space but barely have a budget to work on? If you’re looking for something affordable but still capable of doing the job, how about the simple, budget friendly Skywatcher HERITAGE-100P T Parabolic Dobsonian Telescope?


TELESCOPES



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SAXON DOBSONIANS
6" Dobsonian $390AUD
8" Dobsonian $590AUD
10" Dobsonian $860AUD
12" Dobsonian $1390AUD
- COLLAPSIBLE 8" DOBSONIAN $560AUD
- COLLAPSIBLE 10" DOBSONIAN $860AUD
- COLLAPSIBLE 12" DOBSONIAN $1585AUD


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GM-8 with stepper motors $CALL
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Optics and Who It Is For

These specs mean that this telescope is going to give extremely clear views of the very distant universe. The image quality, if tuned correctly, is going to be extremely crisp and give you views that you won’t be able to get with any other telescope.

With the massive size, high lowest magnification level and low focal ratio this telescope are not going to do some standard things, like look at the moon, very well. It is specifically designed to sit and stare into deep space, not near space.

It’s stated intended use is to look at distant galaxies according to a leading telescope site. Distant galaxies. That means it is not even best intended to look within our own galaxy. That kind of power also comes with a bit of a caveat.

As cool as these specs are and as awe-inspiring as the size of this scope is, it is not going to be for everyone. This telescope is going to be the end of the road for the enthusiast who has continued to get larger and larger reflectors over the years as they’ve honed their skills and refined their interests.

Dobsonians already fill a sort of niche for those astronomers who love the deep space ability of reflectors who want to take that ability as far as they can in a residential setting. These telescopes are fondly referred to as light buckets by their users who have set them up to soak up as much light from the cosmos as possible.

A look at the size

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If that is not you, then you probably don’t need a Dobsonian much less the largest Dobsonian out there.

That being said, if light buckets are your thing and you have graduated on to the largest sizes and yearn for more deep space then this could be the last telescope you ever need to buy.

It can show you the Andromeda as never before, you can fill your eyes with the structures and sights of distant galaxies and star clusters usually only seen on a computer screen by most people. See satellite galaxies around larger ones. View the arms of nearby spiral galaxies or the hazy glow of cluster galaxies.

If you want to peer deep into space and back in time, not because you know what’s out there but because you don’t know what’s out there this telescope is for you. A lot of astronomers find the name of some object, Perseus, Polaris, Saturn, The Crab Nebula and then they set out to find it and look at it. The stuff you’ll be seeing with this scope does not have colloquial names in a lot of cases, they’re going to be categorized by strings of letters and numbers.

You won’t know what you’ll be looking at, at first and that’s okay. That’s part of the adventure and the fun of this telescope. You are going to look far beyond what the average astronomer sees into the realm where only the scientists frequent.

This kind of astronomy is not for everyone, and that’s okay. It won’t be great for children or beginners just starting out. It will not be good for people with limited space or resources or people with light-polluted skies. But for the right kind of astronomer, it is going to absolutely blow their minds.


Taurus Dobsonian Telescopes

Taurus Dobsonian telescopes are offered from Taurus Telescopes, a Polish telescope manufacturer of ultralight, compact Dobsonian telescopes from 14” – 24”.

Taurus is now offering digital setting circles (DSCs) for their line of Dobsonian telescopes. This accessory provides the telescope with constant information about the position of its axes. Simply connect your smartphone to the telescope and in a planetarium app you can see which area of the sky your telescope is looking at. Find an interesting object in the planetarium app and let your smartphone show you how to PushTo the telescope in order to observe this object through the eyepiece.

Owners of Taurus Dobsonian telescopes can buy the DSC kit to retrofit their telescopes. New Taurus models are available with pre-installed DSC as an option.

The Taurus Dobsonian telescopes DSC System specifications include:

– Works with Knightware, SkySafari, SkyMap Pro, Stelarium, TheSky and other software.

– Compatible with iOS (iPad, iPhone, MAC), Android and Windows devices.

– Communication via Bluetooth or WiFi. Up to 4 devices can be connected simultaneously.

– 5V power supply via USB or 5-9V power supply (No power supply included)

– High resolution 8192 PPR encoders

– 3 LEDs indicating Bluetooth, WiFi and power status

The Taurus DSC System standalone package includes:

– 2 high-resolution capacitive 8192 PPR encoders with adapters and assembly kit

DSC module

– Wires for connecting encoders

– Unscrewed aluminum arm for mounting the encoder in the ALT axis

– 2 axes with machine bearings

Taurus Telescopes are made to order individually so that upgrades like secondary mirror heating, digital setting circles and a primary mirror cooling fan can be included upon order. You can learn more here.

And to make it easier for you to get the most extensive news, articles and reviews that are only available in the magazine pages of Astronomy Technology Today, we are offering a 1 year magazine subscription for only $6! Or, for an even better deal, we are offering 2 years for only $9. Click here to get these deals which only will be available for a very limited time. You can also check out a free sample issue here.


FINISHED TELESCOPES

This gathering represents the largest telescopes to be made in the class at the time. They include two 16 inch, two 20 inch and a 28 inch.

El Camino College at the annual Riverside Telescope Makers Conference

Once a year, El Camino College students can enter their finished telescopes in the Riverside Telescope Makers Conference. The conference occurs every Memorial Day weekend in Big Bear, CA.

25 inch Newtonian Truss Tube Design

This 25" Newtonian won a Merit award at the 2000 Riverside Telescope Makers Conference for its hand made optics and overall design.

Fun for the Whole Family

This customize telescope won a certificate of appreciation at the 2004 Riverside Telescope Makers Conference

An 6 inch Newtonian on a Dobsonian Mount

Most students make this kind of telescope due to its portability and low cost.

Large Aperture Telescopes

16" truss tube, dobsonian design with 6" newtonian telescope "piggybacked" on top.

Our Astronomy 13 instructor, completed this 28 inch Dobsonian telescope as part of this class. Many other large aperture telescopes have been completed including four 16 inch, two 20 inch telescopes and a 25 inch.

6 inch, f/10 first scope

With a long focal length and wooden dobsonian base, this is a fine example of a first hand-made telescope.

Portable 8 inch Truss Tube Dobsonian

This eight inch telescope has two supporting truss tubes for a compact and portable design.


  • "You Silly Goose!" Building a Telescope with John Dobson. Learn what it's like to take John Dobson's telescope making course.
  • Dobsonian Telescope: Photo Gallery. See a typical home-built Dobsonian telescope up close.
  • Notes from John Dobson's Telescope Making Class. You can use these "cliff's notes" from John Dobson's class to help you build your scope, whether or not you take the course. Hosted by Sidewalk Astronomer-emeritus Ray Cash. . John Dobson designed this variation of his original telescope for looking at the Sun safely.
  • Build a Solar Filter for Your Telescope. You can build this inexpensive solar filter to convert your nighttime Dobsonian for daytime Sun viewing.

You can also purchase printed plans and John Dobson's telescope making video directly from the Sidewalk Astronomers national website.


The Lake County Astronomical Society

In separate article, I wrote about correcting the problem of the club's telescope not holding its position in altitude. The resolution boils down to the fine art of adjusting the equilibrium point of the tube and providing just the right amount of friction in the mounting. If you have a Dobsonian-mounted scope of your own, then you're familiar with the situation. Several years ago, we added a new focusing mount and a finder. This necessitated moving the primary mirror closer to the secondary and shortening the tube by a couple of inches. Since the scope was now out of balance, we moved the altitude bearings. Then a couple of years ago, the finder was replaced with a Telrad, and that slightly changed the balance again. Rather than try some more counterbalancing, I opted to tinker with the mounting. On each side of the tube there are teflon pads that bear against the inner sides of the rocker box when the scope is aimed from about 30 o from the horizontal on up to the zenith. Through friction against the wooden box, these pads provide some braking action. However, as the scope swung higher overhead, the pads now bore against the sides with decreasing pressure, allowing the telescope tube to move too freely. This was caused due to the rocker box not being perfectly square perhaps the sides have warped outward slightly. The solution was to add a piece of 1/16" thick copper clad circuit board material on one of the inside surfaces of the rocker box where a teflon pad bears against it. This keeps the scope from slipping and seems to have smoothed out the altitude motion somewhat. This material came from my junk drawer (origin unknown), but you probably could find similar stuff at places like the American Science Center or Harrison Supply in Wheeling.

In a situation where a Dobsonian telescope is slightly out of balance, a common solution is to add counterweights along the tube or on one end to achieve the desired equilibrium. Some observers even achieve a temporary fix by taping a crescent wrench or other heavy object to the tube in order to balance it while using a large eyepiece! But any permanent addition of weights is fraught with other problems, not the least of which is that the telescope now becomes that much heavier and less manageable. And as the telescope swings about the altitude axis, the point of equilibrium is constantly changing. Adding weights along the tube works well for the short tubed Schmidt-Cassegrains, but on longer tubed Dobsonians, the counterbalancing effect of the weight changes slightly as the effective moment arm shifts with tube rotation. This can result in the telescope tube having an annoying mind of its own when you try to make subtle movements to follow an object in the eyepiece. The following is an over-simplified illustration of what happens with a weight mounted at the base of the telescope tube. Of course, the force exerted by the weight of the upper part of the tube is also affected by movement around the altitude axis.

Some telescope builders make the weights easily moveable, which also helps as accessories are added. On a German equatorial mount, this can be accomplished by repositioning the counterweight on the declination axle and/or for-and-aft movement of the tube in its saddle. If the out-of-balance condition isn't severe, a good solution is to provide some braking action by adding friction or an adjustable clutch on the axes of the mounting. With the club scope, we added friction by "tightening" the rocker box 1/16 of an inch (the thickness of the circuit board). A similar problem occurs with equatorial mounts that are too flimsy to hold the telescope in place as it's aimed toward different areas of the sky. An axle riding in a sleeve generally has more friction in direct proportion to the surface area in contact. In fact, many of us set out to build a smoothly-operating telescope, only to be surprised to find that it moves too easily. Some friction has to be added to ensure that it stays where it's aimed without constantly putting on and taking off counterweights.

Another catch-22 can occur when using a lightweight, thin mirror in a Dobsonian-mounted telescope. To use the more efficient low-to-the-ground rocker box, you have to add a substantial counterweight at the primary mirror end in order to balance the telescope. But then you've just defeated one of the two advantages of the lightweight mirror! (The other advantage is lower cost.)


A Dobsonian Telescope is simplicity in itself a simple set of optics on a simple mount. But don’t be fooled by this simplicity. Dobsonian telescopes are incredibly good and are great for amateurs and professional astronomers alike. They are also very economical compared to other telescopes.

The optical part of the telescope or OTA (Optical Tube Assembly) is the same as a Newtonian reflector telescope. It consists of a primary parabolic mirror and a flat secondary mirror in an open-ended tube, with a focuser for an eyepiece set on the side. Light enters the tube, reflects off of the primary mirror at the base and is then focused onto the smaller flat secondary mirror and then finally, into an eyepiece. Simple!

The benefit of this type of optical arrangement is the telescopes light gathering ability. The more light gathered, equals more fainter objects to be seen. A light bucket!

Dobsonian/Newtonian telescopes have a big advantage over telescopes with lenses such as refractors and Cassegrain telescopes, as mirrors are a lot cheaper to make than lenses. Plus they can be a lot bigger!

Both Dobsonian Telescopes and Newtonians are measured by the size of the diameter of their primary (big) mirror. Dobsonian sizes range from starter scopes of 6 inches up to 30 inches, but common sizes are 8 to 16 inches in diameter. They can be many times larger and less expensive to produce than scopes with lenses. The second part of a Dobsonian Telescope is the mount. As with the optical part the mount is just as simple, if not more so! A basic manual mount which supports the optical tube and can be manually moved by hand in the Altitude (up/down) and Azimuth (left/right) axis.

The mount is usually made from wood or metal with bearings and support for the two axis of movement. More so lately, some manufacturers have put GoTo systems with motors on some Dobsonian mounts. Personally I think it’s a bit over kill for a Dobsonian telescope, as finding objects manually by star hopping or other manual methods helps you learn the sky better and can be fun.

Resist the urge to spend lots of money on small computerized scopes that will eventually never get used, as they can be too complicated or you may not see much through them apart from the brightest objects such as the Moon. A Dobsonian telescope is a great all-around telescope, and are available in almost all telescope stores. Some people make their own homemade Dobsonian scopes too!

Due to the nature of the Alt-Az mount, Dobsonians are not suitable for long exposure astro imaging. For that you will need an equatorial mount, which will track the stars equatorially. You may have some success with webcam imaging with some of the GoTo Mounts though.

Benefits of Dobsonian Telescopes

Dobsonian telescopes are designed to be simple, easy to use and gather as much light as possible. Because of this robust simplicity, they are very economical and popular with astronomers of all levels of ability. My own and most favourite scope is my Skywatcher 10-inch Dobsonian Telescope and I will probably be using it for many more years to come, as it is difficult to beat! Please browse the excellent range of Dobsonian Telescopes here.

The name of the Dobsonian Telescope comes from its creator John Dobson, who combined the simple design of the Newtonian telescope with the Alt-Azimuth mount. He originally made simple homemade scopes from household materials and ground mirrors out of the glass of old ship portholes.

John Dobson is the grandfather of Sidewalk Astronomy and co-founder of the San Francisco Sidewalk Astronomers.


Reviews for "The Dobsonian Telescope":

Sky and Telescope, October 1998

"It belongs on the shelf of every amateur telescope maker, and for that matter every Dobsonian owner. With its whimsical style and thorough treatment of the subject the book is destined to become a classic. "

[email protected] from Santa Fe, New Mexico, 03/03/98

Outstanding guide for constructing a Dobsonian Telescope. If you've ever considered making your own large telescope, this book is the definitive tome. It discusses the practical considerations for building a large amateur telescope with materials mostly available at hardware stores. More important than construction details, the design criteria and simple theory are discussed in detail, so that the builder can intelligently modify the design and innovate new variations on this design. What's remarkable about the book is that it covers construction techniques in detail by one of the leading manufacturers of large Dobsonians and no holds seem to be barred. It's clear that the authors' motive is spreading interest in telescope making and their effort reflects the etymology and highest meaning of the word "amateur". My only quibble is that the authors downplay the rewards of grinding one's own telescope mirror. This topic is covered in an appendix, but further "pride in manufacture" and significant cost savings can be achieved by making your own mirror and it is not such a daunting task. The book is richly illustrated, engagingly written, and an excellent value for $29.

[email protected] from Virginia, United States, 05/04/98

"The Book" if you're thinking about building a telescope. Excellent, interesting, and practical treatment of how you can build a state of the art, large to "giant"(8" to 40"+ aperture!) portable telescope. Uses the right amount of thorough well written engineering theory to justify the surprisingly simple component designs, materials, and construction techniques. The authors clearly want you to succeed. If your contemplating building a telescope based on your preconceptions, forget them, and read this book. The dobsonian approach featured here is a relatively recent major breakthrough in telescope design that few in the general public are aware exists. I can't imagine a "hotter" garage project for a dad to get into with his son or daughter.

Paul Greenhalgh (President) Fraser Valley Astronomers Society British Columbia Canada

I thought I'd drop you a note to say "THANK YOU" for publishing your wonderful book on how to build an Obsession. As much as we would have loved to purchase one of your beautifully constructed and hand crafted telescopes, as well as support your wonderful company, alas it was to be an impossibility. Our humble club couldn't raise the funds needed to do so. Your unselfish act of publishing this excellent book, made our "wanting" dreams a reality! Our new 20" Obsession style telescope is truly beauty. An absolute breeze to use. the result has been fantastic. I also want to thank you so very much, for your speedy assistance, in getting us the parts we needed, ie: Upper Truss Tube Clamps and Aluminum Side Bearings. The speed in which they arrived was absolutely outstanding! I CAN'T WAIT FOR FIRST LIGHT! Are we Obsessed yet? Dam Straight we are! And it's all thanks to you. She's Obsession alright, but built by FVAS members who followed your book to the absolute letter! AWESOME. Clear Skies!


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This will always be a permanent part of my telescope reference collection.

If you are considering building a dobsonian telescope, this book is mandatory. While somewhat dated, the detailed information on everything from grinding mirrors to loading issues on equatorial mounts is invaluable. David Kreige makes telescopes for a living and damn good ones at that. I'm actually surprised at the number of "trade secrets" he discusses openly in the book and the pitfalls that will ensnare you if you neglect to read the book fully. The best time and money you can spend on a scope, is but this book, read it cover to cover and then consider building your own scope to meet you needs. I've built four Dobson scopes and all have been rewarding. With this book now in hand, I intend to explore the potential for a 24-30 inch Dobson for serious sky work after retirement. By the way , this is my second copy of the book. I've loaned my first one out so many times, it falling apart! См. весь отзыв

All ya need to build a Dobsonian!

This book fantastically details the what, how and why of building a Dobsonian, large and small. Just pulling plans off the internet leaves big holes in the knowledge base needed to build a telescope. This book fills in all those holes and gives you everything you need to design and construct your dream Dob. Totally recommended!

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Great Telescope Construction Guide!

The Dobsonian Telescope by David Kriege, Richard Berry (1997) is the most comprehensive book Imaginable on the subject of Designing & building a Dobsonian type telescope. Every facet of design, and construction is covered, it is a truly complete guide. The text is easily read and understood and there are many, many tables, drawings and photos illustrating the way, step by step. I thought I already knew a lot about Dob scopes, but the amount of information and ideas in this book blew me away! If you are planning on building or improving an existing Dob telescope, this book is worth it's weight in eyepieces! Don't build a scope without it! Astroartist56 9/29/08