How To Make Telescopes

Have you ever looked at the stars and wondered how to make telescopes yourself? It’s a project that combines creativity with science, allowing you to build a tool for personal exploration. This guide will walk you through several methods, from simple beginner projects to more advanced builds. You’ll learn that crafting your own telescope is an achievable and deeply rewarding experience.

You don’t need a professional workshop to start. With some basic materials and patience, you can assemble a functional telescope. We’ll cover the essential optics, the different types of telescopes, and clear step-by-step instructions. Let’s begin your journey into amateur telescope making.

How To Make Telescopes

The core of any telescope is its ability to gather and focus light. To make a telescope, you fundamentally need two optical components: an objective lens or mirror to collect light and an eyepiece to magnify the focused image. The method you choose depends on your budget, skill level, and what you want to observe.

Understanding Telescope Optics

Before gathering materials, it’s crucial to understand the basics. A telescope’s power comes from its aperture—the diameter of its main light-gathering lens or mirror. A larger aperture collects more light, allowing you to see fainter and more detailed objects.

Magnification is secondary and is determined by the combination of the telescope’s focal length and the eyepiece. You calculate it by dividing the telescope’s focal length by the eyepiece’s focal length. For example, a telescope with a 1000mm focal length using a 10mm eyepiece gives 100x magnification.

Key Optical Components

Objective Lens: Used in refractor telescopes. It’s the front lens that bends (refracts) light to a focus point.
Primary Mirror: Used in reflector telescopes. This concave mirror at the bottom of the tube reflects light to a focus point.
Eyepiece: A small lens assembly you look through. It magnifies the focused image from the objective. Interchangeable eyepieces provide different magnification levels.
Focuser: A mechanical holder that allows you to move the eyepiece in and out to achieve a sharp image.

Method 1: A Simple Refractor Telescope from Lenses

This is a great first project. It uses inexpensive lenses to create a working refractor telescope. It’s perfect for lunar and terrestrial viewing.

Materials Needed

Two magnifying glasses (a large one for the objective, 2-3 inches diameter, and a smaller one for the eyepiece)
Two cardboard tubes (one should slide snugly into the other; a mailing tube and a paper towel roll often work)
Strong tape (electrical or duct tape)
Scissors or a craft knife
A ruler
Black paint or construction paper (to line the inside of the tube, reducing internal reflections)

Step-by-Step Assembly

Prepare the tubes. If the insides are not black, line them with black paper or paint them. This step is important for image contrast.
Attach the large objective lens. Secure it over the end of the larger tube using a crisscross of tape. Make sure it is centered and held firmly.
Attach the smaller eyepiece lens. Tape it securely over the end of the smaller tube.
Slide the smaller tube (eyepiece tube) into the larger tube (main tube). They should fit snugly but still able to slide for focusing.
To use, point the objective lens at a distant object. Slide the inner tube back and forth until the image comes into sharp focus. You will likely see an upside-down image—this is normal for simple astronomical telescopes.

Method 2: A Basic Newtonian Reflector Telescope

This is a more advanced but classic project. Newtonian reflectors use mirrors instead of lenses, offering more aperture for your money. Building one involves a bit more precision.

Essential Components to Source

A parabolic primary mirror (with a focal length of, for example, 1200mm and an aperture like 114mm or 150mm)
A flat secondary mirror (elliptical shape)
Eyepiece (a Plossl 25mm or 10mm is a good start)
A focuser (a simple 1.25-inch rack-and-pinion)
Cardboard concrete form tube or PVC pipe for the main tube (diameter must match your primary mirror size)
Mirror cells (to hold the primary and secondary mirrors)
Spider (the vanes that hold the secondary mirror in the center of the tube)
Finderscope (a small, low-power telescope for aiming)
Wood for a simple Dobsonian mount (the simplest, most stable mount for a reflector)

Building the Optical Tube Assembly

Build the Mount First: Surprisingly, start with the Dobsonian mount. It’s a simple box-and-rocking design made from plywood. Having a stable place to put your tube is essential before assembling the optics.
Prepare the Tube: Cut your main tube to length. The ideal length is slightly shorter than the focal length of your primary mirror to allow for focusing. Paint the inside with flat black paint.
Install the Primary Mirror: Mount the primary mirror into its cell. Then, attach the cell to the bottom end of the tube. The mirror’s face should point up the tube.
Install the Spider and Secondary: Carefully attach the spider to the inside of the tube, about 1/3 of the way down from the top opening. Mount the secondary mirror onto the spider, angled at 45 degrees toward the focuser location.
Install the Focuser: Cut a hole in the tube at the point where the secondary mirror will reflect the light. The hole’s distance from the primary mirror is critical—it should be where the focused light cone comes to. Attach the focuser securely over this hole.
Align the Mirrors (Collimation): This is the most critical step. Using a collimation cap or laser collimator, adjust the tilt of both the primary and secondary mirrors until they are perfectly aligned. This ensures all light is directed cleanly into the eyepiece.

Choosing and Using Your Eyepieces

Eyepieces are your telescope’s interface. A good set is vital. They are characterized by their focal length (in millimeters) and field of view.

Long Focal Length (e.g., 25mm-32mm): Provides lower magnification, wider views, and is easier to look through. Perfect for finding objects and viewing large nebulae.
Medium Focal Length (e.g., 10mm-18mm): Offers medium magnification. Good for general lunar, planetary, and star cluster viewing.
Short Focal Length (e.g., 4mm-9mm): Provides high magnification. Use for planets and the Moon on nights of steady atmospheric “seeing.”

Always start with your lowest power eyepiece to locate an object. Then, you can switch to a higher power one for more detail, if the conditions allow it.

Building a Stable Mount

A wobbly mount ruins any telescope. For the Newtonian reflector described, a Dobsonian mount is ideal. It’s an alt-azimuth design (moves up-down and left-right) made from wood and Teflon pads.

Simple Dobsonian Mount Parts

Two pieces of plywood for the base (side panels)
A bottom board and a top (azimuth) board
An altitude bearing (you can use large Formica-covered circles attached to the tube)
Teflon pads or kitchen cutting board material for smooth friction surfaces
Central pivot bolt for azimuth movement

The design allows for silky-smooth movement with just the push of a finger, holding the tube steady in any position. There are many free plans available online for specific mirror sizes.

Aligning and Testing Your Telescope

Once assembled, you must align the optics—a process called collimation. For a reflector, this is non-negotiable for good performance.

Point the tube at a bright star or during the day, a very distant object.
Insert a medium-power eyepiece and defocus the star slightly. You should see a series of concentric circles (diffraction patterns).
If the circles are not centered, use the adjustment screws on the primary mirror cell to carefully center them. This might take a few tries to get right.

For your first light test, aim at the Moon. It’s an easy and spectacular target. Then try a bright planet like Jupiter or Saturn. You should be able to see Jupiter’s moons and Saturn’s rings with a well-built 6-inch reflector.

Common Troubleshooting Tips

Blurry Images: Check collimation. Ensure the telescope is properly focused. Also, allow your scope to cool down to outside temperature to avoid tube currents.
Image is Too Dim: You might be using too high a magnification for the object or conditions. Switch to a lower power (longer focal length) eyepiece.
Tube is Wobbly: Tighten all bolts on your mount. Ensure the altitude bearings are snug against the Teflon pads.
Can’t Find Anything: Always start by aligning your finderscope in daylight. Point the main tube at a distant object, center it, then adjust the finderscope’s screws until it’s centered on the same object.

Safety and Maintenance

Never, ever point your telescope at the Sun without a professionally designed solar filter that fits over the front of the telescope. An eyepiece solar filter can crack from the heat and cause instant, permanent eye damage.

Store your telescope in a dry place. Cover the open ends of the tube to keep dust out. Clean optics only when absolutely necessary, using proper lens cleaning fluid and microfiber cloths in a gentle, circular motion. Mirrors rarely need cleaning.

Taking Your Skills Further

Once you’ve completed a basic build, the world of amateur telescope making (ATM) opens up. You can learn to grind and polish your own mirrors, build more complex equatorial mounts, or even try making a compound telescope like a Schmidt-Cassegrain. Joining a local astronomy club is the best way to get advice, inspiration, and access to specialized tools.

FAQ Section

What is the easiest type of telescope to make at home?

The simplest is a basic refractor using two magnifying glasses and cardboard tubes. It introduces the core concepts without needing precise alignment.

How much does it typically cost to build a telescope?

A simple lens telescope can cost under $20. A 6-inch Newtonian reflector with purchased mirrors and basic parts can range from $200 to $400, still often cheaper than a comparable commercial model.

Can I make a powerful telescope that sees planets clearly?

Yes. A homemade 6-inch or 8-inch Newtonian reflector on a Dobsonian mount is exceptionally capable for planetary viewing. It will show Jupiter’s cloud bands, Saturn’s rings, and lunar craters in great detail under good skies.

Is it hard to make a telescope mirror?

Mirror grinding is a dedicated craft requiring patience, but it’s very achievable. It involves grinding a glass blank with abrasives to a precise parabolic shape. Kits are available with all the needed materials and instructions.

Why is my homemade telescope showing upside-down images?

Simple astronomical telescopes often do this because they use the minimum number of optical components. Adding an erecting prism or lens assembly can correct it, but it adds cost and complexity and is not needed for stargazing.

How long does it take to build a telescope?

A simple refractor can be made in an afternoon. A Newtonian reflector with a Dobsonian mount, working carefully, might take a dedicated weekend or several weekends if you’re sourcing parts and building everything from scratch.