Stargazing on a clear night is one of the most ethereal experiences that you can have, whether that is on your own or with your loved ones. Your options range from a local observatory to a homemade Dobsonian Telescope.
A Dobsonian telescope is your portable tool for observing star clusters, constellations, and deep-sky objects. Hence, building your own is worth the effort.
If you are wondering how to build a Dobsonian Telescope at home, this is the guide for you.
Another portable stargazing option are binoculars. Check out the best 10×50 Binoculars for astronomy.
What is a Dobsonian Telescope?
A Dobsonian Telescope, also widely known as Newtonian Telescope, was designed by John Dobson in the year 1965. The design favored amateur astronomers, as it was a simplified version of the extremely technical telescope designs.
The telescope is altazimuth-mounted and operates at low magnifications. Hence, it is cost-effective and portable.
The basic mechanism follows a primary mirror that reflects the incoming light rays and a secondary mirror that focuses those rays through the focuser eyepiece. The telescope’s body is made of construction tubes and is mounted on a plywood box.
Dobsonian Telescopes have large apertures, allowing observers to set up at dark sky locations and observe star clusters with ease. The design incorporated narrow-pass filters and better eye-pieces, alongside the low mass proportions of the telescope itself. This allowed astronomers to study tons of deep-sky objects that they were not able to before due to previous employment of large, immovable telescopes. The simplicity of the design was not just notorious back then, as these telescopes are still easy to assemble and just as popular now. If you are looking into making a homemade Dobsonian telescope, there are DIY Dobsonian Kits available as well as guides and plans that make the entire process fool-proof.
Build Your Own Telescope
If you are reading this, it means you have decided to construct your own Dobsonian telescope at home, and you are virtually lost in the world of technicalities. I am here to assure you to not worry as the process might seem intimidating but once simplified will make much more sense.
Starting off, you have two options to pick from. You can go and build everything from scratch-yes, even the mirrors-or you can purchase a DIY Dobsonian Telescope Kit. The kits range from 6 inches to 12 inch Dobsonian telescopes and will cost you between $300-600.
How much does it cost to build a Dobsonian telescope?
If you choose to build from scratch, the process will cost you less than purchasing kits. Your major investments will be directed towards the mirrors and the Teflon tube. Other materials including tools, plywood, nails, and more are available at the local hardware stores at wholesale prices. In comparison to the kits available, the cost reduction is almost 50% when assembled from scratch.
Materials and tools list
Let’s start off with all the bits and pieces you will need prior to building and assembling the telescope. You will have to decide the size of the telescope mirror that you would like to purchase. The most common plans available are for 8inch and 6inch Dobsonian Telescopes. However, if you want to expand your scope, you can use the plans available and scale them to your desired mirror size.
You will have to initially purchase:
- A primary (objective) mirror that fits at the bottom of the telescope. This mirror captures and focuses the light that is reflected from the object under observation.
- A secondary (diagonal) mirror will be mounted diagonally to the tube’s axis at 45°. This mirror will direct the focused light towards the eyepiece.
Since the size of the secondary mirror depends on the focal length of your objective mirror, you will have to pick the size of your objective mirror first. When you make your purchase, specify the desired size of the objective mirror to which you will be suggested a complementary diagonal mirror size.
Next, you will need the following list of materials:
This is a cardboard tube that’s readily available at hardware stores. One important note to keep in mind is that the sonotube should always be about 2 inches wider in diameter than the size of your mirror.
You can get the hardware stores to cut this tube to fit the desired size of your telescope. In this guide, we will be referring to the 8inch Dobsonian Telescope sizes and plans. Hence, the sonotube for this telescope will be 10 inches in diameter.
2. Mirror Cell:
This can be ordered from the same optical store through which you purchase your primary and secondary mirrors.
A mirror cell is a frame in which the primary mirror is fixed to prevent distortion of the image. The mirror cell can fit inside the primary mirror box, which depends on whether you want to make the additional effort or not.
3. Primary Mirror Box (optional):
This is made out of plywood that is cut and glued together. This box is fitted to the base of the telescope, through which the telescope can rotate vertically. However, the mirror cell can also directly be mounted on the telescope tube. This is an additional detail that can help your Dobsonian telescope go from looking homemade to more professional.
This will be used for the bearings in the secondary and primary boxes. Teflon is a slippery material and allows for smooth movement of the bearings. When used along with Ebony star, the material creates the perfect level of friction to control the movement of the telescope but enough smoothness for it to rotate with ease.
5. Focuser and eye-piece:
This will fit in the upper tube of the telescope along with the secondary mirror. Hence, this will be your tool for viewing the image captured by the primary mirror.
Extra materials and tools:
- Metal screws
- Table saw
- PVC glue
- Tape measure
- Spider for the sonotube
- Lag screw and washer
Dobsonian Telescope Plans
Once you have accumulated all the bits and pieces, it’s time to get to work. The first step to building a telescope from scratch is to go through designs and Dobsonian telescope plans that are available online.
The most common resource for that is “The Dobsonian Telescope: A Practical Manual to Building Large Aperture Telescopes” by David Kriege and Richard Berry. This guide will lead you through the entire process from start to finish, and you can change the dimensions of your project according to the plans present in this manual. Below are some samples of plans used to make the mount and tube for an 8inch telescope.
Building and assembling the telescope
Starting off with the tube, place the spiders on each end of the sonotube. Attach the primary mirror to the mirror cell and fix that to the bottom end of the tube, or in the primary box. Now, you would have to measure the perfect distance at which the secondary mirror will be placed. The primary mirror’s focal length is made up of the distance between the focuser and eye-piece to the secondary mirror, and the distance between the secondary mirror to the primary mirror. Once the calculations are done, you can install both the mirror in their respective positions on the tube.
Now, start building your mount and rocker. Use the design plans to carve out plywood and other tools to build your mount. In the end, your mount looks something like this. The tube box helps keep the sonotube in place.
The sonotube will pass through the tube box that is attached to the rocker. This will allow it to rotate freely on all axis. Next, attach the eyepiece and the focuser to the top part of the telescope tube. Carve out a hole on the top part of the sonotube first. Attach the eye piece to another cardboard piece and pass it through the hole from the inside of the tube. Use glue and nails to attach the eyepiece firmly. Lastly, align your diagonal mirror at the required angle. You should be able to view the entire objective mirror through the angle of the secondary mirror. Assemble the rest of the pieces together, and your telescope is ready! Take it out on a clear night and enjoy looking at the stars in your viewable galaxy.
The entire project will take you a couple of weeks to complete. However, if you purchase Dobsonian Telescope kits, you will be saving time at the cost of your wallet. Some quick tips to note if you are making a homemade telescope are:
- 1. Use mild soap and distilled water to clean the surfaces of the mirrors in the telescope when they collect dust.
- 2. These telescopes are not used for astrophotography. However, if you want to become an astrophotographer but are on a budget, there are many of the best telescopes under 1000$ that you can use for that specific purpose. Or, you can purchase a professional Dobsonian telescope like the Orion Skyguest xt10 for the exact same job.
- 3. For the sonotube, cardboard is the best material. PVC tubes are not durable in the sunlight, as the material can expand.
There you have it! You now have all the basic information required to help build your very own Dobsonian telescope. Whether you build from scratch or use telescope kits, the effort will pay off in the end as you glance up at the ethereal clusters of stars in the night sky. So what are you waiting for?
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