How to Make Telescope at Home DIY
To make a Dobsonian telescope, start by researching designs and choosing a mirror size based on your budget and light gathering needs. Sketch a design, prepare a materials list, and cut plywood or MDF pieces for the mirror and rocker boxes. Assemble the boxes, ensuring the mirror box is light-tight, and build a mirror cell to hold the primary mirror. Construct the rocker box, install bearings for smooth movement, and create a diagonal holder for the secondary mirror. Install the focuser, apply paint or stain, align the mirrors, and you’re ready to explore the cosmos.
For a refractor telescope, research focal lengths for desired magnification and find sturdy tubes to suit the focal length. Cut and assemble the tubes, ensuring a snug fit for focusing, and sand rough edges. Mount lenses on opposite ends of the tube, build a focusing mechanism, paint the inside of the tubes black, and construct a stable tripod for steadier viewing.
Building a simple reflecting telescope involves deciding on magnification, which determines the focal length of the mirrors. Create a mirror cell from cardboard and attach it to the telescope tube. Position secondary mirror at a 45-degree angle to the primary mirror. The telescope tube, eyepiece holder, and sturdy mount are other critical components. Align and collimate the mirrors for proper functioning. Simple materials like cardboard tubes, lenses, and mirrors, along with basic tools, are needed for construction.
How to make a Dobsonian telescope?
To make a Dobsonian telescope follow these 14 steps.
- Research DIY Dobsonian telescope designs online or in astronomy books
- Choose a mirror size based on your budget and desired light gathering capability
- Sketch a design considering the chosen mirror size and height
- Prepare a list of materials
- Use precise measurements to cut the plywood or MDF pieces for the mirror box and rocker box
- Assemble the box sections using wood glue, screws, and clamps
- Ensure the mirror box is light-tight
- Build a mirror cell from plywood or MDF to securely hold the primary mirror
- Assemble the rocker box
- Install the bearings on the bottom of the rocker box for smooth movement on the base
- Create a diagonal holder for the secondary mirror
- Install the focuser on the mirror box
- Apply paint or stain to the exterior of the telescope for a finished look
- Align the primary and secondary mirrors
1. Research DIY Dobsonian telescope designs online or in astronomy books
Research design of Dobsonian telescopes. Online platforms such as Stellafane, Cloudy Nights, and Astronomy Forum offer a wealth of information on DIY telescope making, including tutorials, plans, and resources specifically for Dobsonian designs.
Book “The Dobsonian Telescope: A Practical Manual for Building Large Aperture Telescopes” by David Kriege and Richard Berry is a comprehensive guide that covers materials, design, and construction. Another valuable resource is “Telescope Making” by Albert G. Ingalls, a classic book on amateur telescope making that includes Dobsonian designs and construction techniques. “Amateur Telescope Making” by Stephen Tonkin offers Dobsonian designs and tutorials on materials, making, and adjusting parts from scratch.
When selecting materials and supplies for building your Dobsonian telescope, consider using a portable and adjustable mount, such as a tripod or a pier with a dolly for easy storage and transportation. A motorized equatorial mount can provide precision tracking and control, while a sliding dovetail or twistlock system can ensure a secure connection between the telescope and mount.
2. Choose a mirror size based on your budget and desired light gathering capability
Choose the right mirror size, which primarily determines the instrument’s light gathering power and resolution.
A larger aperture, or mirror size, allows your telescope to gather more light. Larger mirro results in brighter images and the ability to observe fainter celestial objects. It is recommended to start with a 6-inch or 8-inch mirror, as these provide a good balance between cost and performance. Consider opting for larger mirrors such as 10-inch, 12-inch, or 14-inch models if you are looking for better performance.. Keep in mind that larger mirrors come at a higher cost.
To give you an idea of the costs associated with different mirror sizes, here are some estimates: a 6-inch mirror costs between $200 and $400, an 8-inch mirror ranges from $400 to $800, a 10-inch mirror can cost anywhere between $800 and $1,500, a 12-inch mirror falls in the $1,500 to $3,000 range, and a 14-inch mirror can set you back anywhere from $3,000 to $5,000. It’s important to note that moving from an 8-inch mirror to a 10-inch or 12.5-inch mirror significantly increases the light gathering ability of your telescope, and a larger mirror does not necessarily need to be of premium quality to provide this benefit.
The light gathering capability of your Dobsonian telescope is directly proportional to the square of the mirror’s diameter. For example, a 12-inch mirror will collect about four times more light than an 8-inch mirror, resulting in a substantial improvement in the telescope’s performance. Keep in mind that a larger mirror means a larger, heavier telescope, which may require more space and careful consideration regarding portability.
When choosing the mirror size for your DIY Dobsonian telescope project, it’s essential to balance your budget with your desired light gathering capability. Take into account the telescope’s focal length, portability, and storage needs. As a general guideline, a 6-inch mirror is suitable for casual observing, while an 8-inch mirror is recommended for viewing deep-sky objects. A 10-inch or 12-inch mirror is ideal for serious amateur astronomers. For those interested in advanced astrophotography and observing extremely faint objects, a 14-inch or larger mirror would be an excellent choice.
3. Sketch a design considering the chosen mirror size and height
Create a detailed sketch of your telescope design using CAD software or graph paper. Add dimensions, labels, and notes to ensure accuracy and clarity. This will help you build a high-powered homemade Dobsonian telescope that is simple yet powerful.
Calculate the desired height of your telescope. Consider the height of the observer’s eye, which is around 5-6 feet (152.4-182.88 cm). This will ensure that your telescope is comfortable to use and provides a clear view of the night sky.
Design the telescope tube. The inner diameter should be larger than the mirror diameter. For a 12-inch mirror, the inner diameter would be approximately 13 to 14 inches. The tube length should be at least 1.5 times the focal length. For a 12-inch mirror with a 20-inch focal length, the tube length would be approximately 30 to 35 inches.
Design the altitude and azimuth bearings. Position the altitude bearing at a height that allows smooth and comfortable movement, such as 2/3 of the telescope’s height. For a 30-inch high telescope, the altitude bearing would be approximately 20 inches from the ground. Position the azimuth bearing at a height that allows easy rotation, such as 1/2 of the telescope’s height. For a 30-inch high telescope, the azimuth bearing would be approximately 15 inches from the ground.
Plan the rocker box and ground board. The rocker box should be designed to accommodate the altitude bearing and provide a stable platform for the telescope. The box’s height should be approximately 2-3 inches higher than the altitude bearing. The ground board should be designed to provide a stable base for the rocker box and telescope. The board’s size depends on the rocker box’s dimensions and desired stability.
Add the telescope components. Include a finder scope, which is mounted on the side of the telescope tube and around 6-12 inches from the top. Add the focuser, which is located at the top of the telescope tube and around 2-4 inches from the mirror’s edge.
4. Prepare a list of materials
Prepare materials required for building your own Dobsonian telescope.
The optical components are crucial for a powerful and functional telescope. The primary mirror is a parabolic mirror with a diameter of 6-12 inches (15-30 cm) and a focal length of 48-72 inches (120-180 cm). You can either purchase a pre-made mirror or make one using a mirror-making kit. The secondary mirror is a small, flat mirror with a diameter of 1-2 inches (2.5-5 cm), which redirects light to the eyepiece. The eyepiece is a telescope eyepiece with a focal length of 10-20 mm, responsible for magnifying the image.
The mount and base of the telescope provide stability and support. A 1/2-inch (1.3 cm) thick plywood or MDF board, measuring 12-18 inches (30-45 cm) square, is needed for the base. 2×4 lumber is used for constructing the altitude and azimuth bearings. The telescope’s altitude axis is made from a PVC pipe or aluminum rod. Teflon or UHMW bearings are essential for providing smooth motion and low friction.
Other necessary components include a telescope tube, focusing mechanism, counterweight, and assembly materials. The telescope tube, made from cardboard or PVC, has a diameter of 6-12 inches (15-30 cm) and a length of 24-48 inches (60-120 cm), and holds the optical components. A simple rack-and-pinion or helical focuser is used to adjust the eyepiece position. A counterweight, such as a bag of sand or a metal plate, helps balance the telescope. Screws, glue, and paint are needed for assembling and finishing the telescope.
Optional components can enhance the functionality of your Dobsonian telescope. A finder scope, either a small refractor telescope or a red dot finder, can help aim the Dobsonian more accurately. A motor drive, consisting of a DC motor and gearbox, can automate the altitude axis motion for easier tracking of celestial objects.
5. Use precise measurements to cut the plywood or MDF pieces for the mirror box and rocker box
Use high-quality measuring tools to ensure precise measurements when cutting the plywood or MDF pieces for the mirror box and rocker box of a Dobsonian telescope. A high-quality tape measure with a precision of ±1/16 inch (1.5 mm) is recommended by Katz (2017) and Ashby (2017). A combination square and straightedge can be employed for verification, as suggested by Tonkin (2009). These tools will help ensure the accuracy of your markings and measurements.
Creating a detailed cutting plan is another crucial step in achieving precise measurements. Utilize Computer-Aided Design (CAD) software to create precise drawings that include all dimensions and cut angles. This meticulous planning will minimize errors and ensure accurate cuts.
When marking and cutting the plywood or MDF pieces, use a carpenter’s pencil to draw finer cutting lines, which will reduce the margin of error. It is advisable to cut oversized pieces and then trim them to exact dimensions using a router or sandpaper. This technique allows for greater control and precision in the final dimensions.
Use a high-tooth-count saw blade, such as an 80-tooth blade, for smoother cuts and reduced splintering or tearing. Cut slowly and deliberately to maintain control and accuracy throughout the cutting process.
Verification and adjustment of measurements are essential steps in ensuring precise cuts. Verify measurements before cutting and after cutting using precision tools like a caliper and precision square. Make any necessary adjustments to ensure that the components match the design plan.
6. Assemble the box sections using wood glue, screws, and clamps
Before assembling the box sections, prepare the wood parts by ensuring they are clean, dry, and free of debris. Sand the edges to create a smooth surface for gluing.
Apply a thin, even layer of wood glue to the mating surfaces of the box section parts using a brush or applicator. Follow the manufacturer’s instructions for glue application and drying times.
Place the parts together, ensuring proper alignment and fit. Use a combination square to verify the corners are square. Secure the parts together using 2-inch wood screws. Start from the center and work your way outward. Drill pilot holes to avoid splitting the wood.
Apply even pressure using bar clamps, after securing the parts with screws. Ensure the parts are tightly held together. Use C-clamps to reinforce the corners, if necessary.
Let the assembly sit for the recommended glue drying time, 30 minutes to an hour, depending on the glue and environmental conditions.
Inspect the assembly for any gaps or weaknesses, once the glue has dried. Reinforce the joints with additional screws or wood filler, if necessary.
Repeat the process for each remaining box section, following the same steps for assembly.
7. Ensure the mirror box is light-tight
Begin by inspecting the mirror box for any gaps or openings, especially at the joints where the panels meet. Use black silicone sealant to fill these gaps, applying a thin bead of sealant and smoothing it with a credit card. This DIY fix will prevent light from entering the mirror box and affecting your telescope’s performance.
Cover the interior surfaces of the mirror box with a light-absorbing material such as black velvet or flocking paper. Secure the material using a strong adhesive like hot glue or epoxy. This step will further reduce any unwanted light reflections within the mirror box.
Create a light shield by cutting a piece of black cardboard to fit snugly around the mirror box’s opening, leaving about 1 inch of overhang around the edges. Attach this shield using black tape or hot glue. This DIY light shield will block stray light from entering the mirror box during your observing sessions.
Design a removable cover for the mirror box using black plywood or MDF, cutting it to fit the mirror box’s dimensions. Attach a handle and hinges to the cover for easy removal and attachment. This cover will protect the mirror box from light when the telescope is not in use and help prevent dew formation on the mirror.
Apply a light-blocking coating, such as black paint or a specialized coating like Vantablack, to the exterior of the mirror box. This will further enhance the light-tight properties of your Dobsonian telescope.
Wrap the mirror box with a light-absorbing material like black velvet or flocking paper to minimize internal reflections and reduce stray light. Pay close attention to gaps around the mirror cell and focuser, using black silicone sealant or foam tape to fill any gaps.
Apply black paint or tape to the edges to prevent light reflections off the edges of the primary mirror. This simple DIY modification will improve the overall light-tightness of your telescope.
Install a secondary light baffle using a thin piece of black plastic or metal positioned between the primary mirror and the focuser. This baffle will reduce light leakage and further improve the image quality of your Dobsonian telescope during your observing sessions.
8. Build a mirror cell from plywood or MDF to securely hold the primary mirror
Determine the primary mirror’s diameter, thickness, and weight. Consider a 12-inch (30.48 cm) f/5 mirror with a thickness of 1 inch (2.54 cm) and a weight of 5 pounds (2.27 kg). Calculate the mirror’s center of gravity (CG) to ensure proper support; , the CG is around 1/3 of the way from the mirror’s edge for a 12-inch mirror.
Cut out the mirror cell from 1/2-inch (1.27 cm) thick plywood or MDF. The shape can be circular or octagonal, with a diameter larger than the mirror’s diameter. Cut a circle with a diameter of 14 inches (35.56 cm). Cut a hole in the center of the cell to accommodate the mirror’s curvature; the hole’s diameter should be about 1/4 of the mirror’s diameter, which is 3 inches (7.62 cm) in this case.
After cutting the mirror cell, add support rings made from 1/4-inch (0.64 cm) thick plywood or MDF. These rings should be thicker than the mirror’s thickness. For our example, cut three rings with an inner diameter of 12 inches (30.48 cm) and an outer diameter of 14 inches (35.56 cm). Space the rings evenly apart, with the top ring about 1 inch (2.54 cm) from the mirror’s edge and the bottom ring about 1 inch (2.54 cm) from the cell’s bottom.
Attach the support rings to the mirror cell using wood screws or epoxy, ensuring they are evenly spaced and perpendicular to the cell’s surface. Add small clips cut from 1/4-inch (0.64 cm) thick plywood or MDF to hold the mirror in place. Cut six clips with a width of 1 inch (2.54 cm) and a height of 0.5 inches (1.27 cm). Attach the clips to the support rings using wood screws or epoxy, spacing them evenly apart and placing three clips on each side of the mirror’s CG.
9. Assemble the rocker box
The rocker box is a wooden structure that supports the telescope tube and allows for smooth altitude adjustments.
You need 3/4″ thick wood for the rocker box sides, bottom, and top, and 1″ thick wood for the wedge. You require two telescope tube rings, adjustable screws and T-nuts, wood glue, wood screws, sandpaper, and optionally, paint or varnish for finishing.
Start by cutting the rocker box sides. Cut four pieces of 3/4″ thick wood to approximately 12″ x 18″ (30 cm x 45 cm). Cut the rocker box bottom and top. These pieces should also be 3/4″ thick wood, cut to approximately 12″ x 18″ (30 cm x 45 cm).
Assemble the rocker box. Use wood glue and wood screws to attach the sides, bottom, and top together. Ensure that the corners are square and the sides are even to maintain the precision of your telescope.
Cut the wedge. This piece should be 1″ thick wood, cut to approximately 12″ x 6″ x 2″ (30 cm x 15 cm x 5 cm). The wedge will support the telescope tube within the rocker box. Attach the wedge inside the rocker box using wood glue and wood screws, ensuring it is centered and even.
Attach the telescope tube rings to the top of the wedge. Space the rings evenly to fit your telescope tube, and secure them with adjustable screws and T-nuts. This will allow for precise adjustments when you’re stargazing.
For fine-tuning the altitude adjustment, add adjustable screws to the rocker box sides. These screws will help you make small adjustments to the telescope’s angle for accurate tracking of stars.
Sand the entire rocker box to smooth out any rough edges. This step is important for the comfort of the user and the longevity of the telescope. You can paint or varnish the rocker box for added protection and an enhanced appearance.
10. Install the bearings on the bottom of the rocker box for smooth movement on the base
Choose the right bearings for your telescope. Teflon or UHMW (Ultra-High Molecular Weight) bearings are ideal for this application due to their low friction and durability. You will need four bearings, one for each corner of the rocker box.
Attach bearings to the bottom of the rocker box using screws or epoxy. Ensure the bearings are evenly spaced and aligned with the center of the rocker box. The bearings are attached 1-2 inches (25-51 mm) from the edges of the rocker box.
Align the base. Construct the base of your Dobsonian telescope, ensuring it is level and flat. The base consists of a circular or octagonal plate.
Finally, assemble the rocker box and base. Place the rocker box on the base and align the bearings with the center of the base. Gently rotate the rocker box to ensure smooth movement. Adjust the bearings or the base to achieve smooth, frictionless motion.
Apply a thin layer of silicone lubricant to the bearings to reduce friction and increase smoothness. Consider adding a thrust bearing or a lazy Susan bearing to the center of the base for additional stability and smoothness.
11. Create a diagonal holder for the secondary mirror
Creating a diagonal holder for the secondary mirror in a Dobsonian telescope involves designing and fabricating a spider vane assembly that securely holds the secondary mirror at a 45-degree angle to the optical axis. You will need specific materials and tools, as well as following a series of design and fabrication steps.
The materials needed for this step include a 1/4″ (6.4 mm) thick aluminum or stainless steel plate for the spider vane, a 1″ (25.4 mm) diameter aluminum or stainless steel rod for the diagonal holder, M6 or 1/4″-20 screws and nuts, epoxy or strong adhesive, sandpaper, and a drill press.
Create a spider vane with three or four arms, each approximately 1″ (25.4 mm) wide and 1/4″ (6.4 mm) thick. The length of each arm should match the distance from the center of the telescope to the edge of the secondary mirror, which is 6-8 inches (152-203 mm). Once the design is complete, use a jigsaw or bandsaw to cut the spider vane from the aluminum or stainless steel plate, and sand the edges to smooth them out.
Create the diagonal holder by cutting the 1″ (25.4 mm) diameter rod to the desired length, which should be slightly longer than the distance from the center of the telescope to the edge of the secondary mirror. Attach the diagonal holder to the center of the spider vane using M6 or 1/4″-20 screws and nuts, ensuring it is securely attached and perpendicular to the vane.
Use epoxy or a strong adhesive to attach the secondary mirror holder to the end of the diagonal holder, ensuring it is centered and secure. Attach the spider vane assembly to the telescope’s optical tube using M6 or 1/4″-20 screws and nuts, ensuring it is securely attached and aligned with the primary mirror.
12. Install the focuser on the mirror box
Ensure the mirror box is properly assembled, and the primary mirror is securely attached. The mirror box should have a flat, smooth surface for mounting the focuser.
Measure the distance from the mirror’s center to the edge of the mirror box. Typically, this distance is around 1/3 to 1/2 of the mirror’s diameter (e.g., 4-6 inches for a 12-inch Dobsonian).
Mark the center of the focuser’s mounting flange on the mirror box at the determined distance using a ruler or caliper. Ensure the mark is perpendicular to the mirror’s surface.
Drill three evenly spaced pilot holes (about 1/16 inch or 1.5 mm in diameter) around the marked center. These holes will accommodate the focuser’s mounting screws.
Place the focuser over the pilot holes, ensuring it is centered and even. Secure the focuser using three screws ( 1/4-20 or M6), tightening them in a star pattern to avoid damage.
Check the focuser’s alignment by looking through the telescope. Ensure the focuser is perpendicular to the mirror’s surface and parallel to the optical axis. Make any necessary adjustments to the focuser’s position.
Apply a thin layer of adhesive (e.g., epoxy or silicone) to the interface between the focuser’s mounting flange and the mirror box for additional security.
Verify the focuser’s alignment and attachment by checking the telescope’s optical performance. Make any necessary adjustments to achieve optimal performance.
13. Apply paint or stain to the exterior of the telescope for a finished look
Apply a primer if you plan to use paint. Choose a primer designed for wood or metal, depending on the material of your telescope. The primer creates a uniform base and improves adhesion, allowing for a more professional-looking finish. Be sure to follow the manufacturer’s instructions for drying time.
Apply high-quality, exterior-grade paint or stain using a high-quality brush or roller. Opt for a color that complements the design or suits your personal preference. Apply thin, even coats, allowing each coat to dry before applying the next. After the final coat, let the paint or stain cure according to the manufacturer’s instructions.
Apply a clear coat to provide extra protection and a glossy finish. For wooden components, use a water-based polyurethane, and for metal parts, use a clear acrylic spray. Apply a thin, even coat and follow the manufacturer’s instructions for drying. Consider applying a second clear coat for a more durable and glossy finish.
14. Align the primary and secondary mirrors
Identify the primary and secondary mirrors. The primary mirror is the larger mirror, located at the bottom of the tube in a Dobsonian telescope. The secondary mirror is the smaller mirror, attached to the spider vanes near the top of the tube.
Begin by collimating the secondary mirror. Look through the telescope’s focuser and observe the reflection of the primary mirror in the secondary mirror. The secondary mirror should be perpendicular to the telescope’s optical axis. Adjust the secondary mirror’s tilt screws to center the primary mirror’s reflection within the secondary mirror’s circular outline. Using a collimation tool or a Cheshire eyepiece can help you achieve precise alignment.
Once the secondary mirror is collimated, it’s time to align the primary mirror. Look through the focuser again and observe the reflection of the secondary mirror in the primary mirror. Adjust the primary mirror’s tilt screws to center the secondary mirror’s reflection within the primary mirror’s circular outline. A laser collimator or a precision alignment tool can be used for accuracy.
Verify mirror alignment by observing a bright star or a distant object through the telescope. If the image appears distorted, make adjustments to the mirrors and re-check the image until it appears sharp and symmetrical.
How to make a refractor telescope?
To make a refractor telescope follow these 10 steps.
- Research focal lengths for your desired magnification and budget
- Find sturdy tubes to suit focal length
- Cut and assemble the tubes to the desired length
- Ensure a snug fit for focusing
- Sand any rough edges for a smooth finish
- Mount each lens to opposite ends of the tube
- Build a focusing mechanism for the smaller lens tube
- Use rack and pinion gears or a simpler friction fit that allows sliding the tube in and out
- Paint the inside of the tubes black to minimize internal reflections
- Build a stable tripod to hold your telescope for steadier viewing
1. Research focal lengths for your desired magnification and budget
Determining the appropriate focal length for your refracting telescope begins with deciding your desired magnification level. A simple rule to follow is aiming for a magnification of 2-3 times the aperture of your telescope in inches. This ensures that you achieve a large magnification without compromising the image quality.
To calculate the focal length required for your desired magnification, you need to understand that magnification is determined by the ratio of the telescope’s objective lens focal length to the eyepiece’s focal length. You can employ a simple formula to calculate the focal length: Focal Length (FL) = Magnification x Eyepiece Focal Length (EFL). For instance, if you want a magnification of 150x and your eyepiece has an EFL of 15mm, the required focal length would be 150 x 15mm = 2250mm.
Budget constraints are an essential factor to consider when determining the appropriate focal length for your refracting telescope. Longer focal lengths often require larger, more expensive lenses. A longer focal length necessitates a more robust and expensive mount to support the weight of the telescope.
2. Find sturdy tubes to suit focal length
The material and construction of the tube are vital considerations for a stable and durable refractor telescope. Opt for sturdy materials like aluminum or carbon fiber, which provide necessary stability and support for the lens and other components.
Ensure the tube has a wall thickness of at least 1 mm to 2 mm for sufficient rigidity. These materials are not only robust but resistant to thermal expansion and contraction, helping maintain the tube’s shape and size over a range of temperatures. This ensures that the telescope’s optical alignment remains stable.
Preventing vignetting is another crucial aspect of building a refractor telescope. Vignetting occurs when the tube is too narrow, obstructing the light path. To avoid this issue, ensure the tube’s inner diameter provides enough clearance. A general rule of thumb is to choose a tube with an inner diameter of at least 1.5 to 2 times the diameter of the lens (Smith, 2017). For example, a tube with an inner diameter of 120 mm to 160 mm would provide comfortable clearance for an 80 mm lens, preventing any vignetting or obstruction of the light path.
3. Cut and assemble the tubes to the desired length
Measure and mark the tubes to ensure accurate lengths for each section. Use a precision ruler or caliper to measure the required length of each tube section. Mark the cutting point on the tube with a marker or scratch awl, making sure the mark is perpendicular to the tube’s axis to avoid angular errors.
Cut tubes using a tube cutter or hacksaw specifically designed for cutting aluminum or steel tubes. For a clean cut, apply a small amount of cutting oil or lubricant to the cutting area. Cut the tube slowly and steadily along the marked line. After cutting, deburr the cut edge using a deburring tool or file to remove any sharp edges and ensure smooth connections.
Begin by cleaning and degreasing the cut ends of the tubes with a solvent and lint-free cloth. Apply a thin layer of telescope tube adhesive or epoxy to the cut ends, following the manufacturer’s instructions. Align the tubes carefully to maintain the optical axis using a telescope tube alignment tool or precision jig. Slide the cut ends into each other, ensuring a snug fit.
Use set screws, retaining rings, or adhesive, depending on the telescope design and requirements. Clamp the assembled tubes with a tube clamp or precision jig, applying even pressure to ensure a secure bond. Allow the adhesive or epoxy to cure for the recommended time, 24 hours.
4. Ensure a snug fit for focusing
Make sure that the eyepiece thread size matches the telescope’s focuser thread size, which commonly comes in 1.25 inches and 2 inches. If the sizes do not match, use an appropriate adapter to ensure a proper connection.
Before attaching the eyepiece, inspect and clean both the eyepiece and focuser to remove any debris, dirt, or oil. Use a soft brush or cloth for gentle cleaning. Applying a thin layer of silicone-based lubricant to the threads of the eyepiece or focuser can help reduce friction and ensure smooth operation when making adjustments.
To thread the eyepiece carefully, screw it into the focuser by hand. Be cautious not to overtighten, as this can damage the components. Instead, stop when the eyepiece feels snug but still allows for smooth rotation. This twistlock mechanism will help maintain the alignment and focus of your DIY telescope.
Check the eyepiece’s position to ensure it is properly seated and centered in the focuser. Adjust the eyepiece as needed to achieve optimal alignment. This step is particularly important when operating the telescope remotely, as any misalignment can affect the quality of your observations.
5. Sand any rough edges for a smooth finish
Start by cleaning the tube thoroughly with a soft brush and mild detergent to remove any debris or oils. Next, use 120-grit aluminum oxide sandpaper to sand the tube, working from the inside out in a linear motion, following the length of the tube.
After sanding with coarse grit, progress to finer grits, gradually moving to 220-grit, 320-grit, and 400-grit sandpaper. Repeat the same linear motion to achieve a smooth finish. Once the tube is smooth, polish it with a metal polish, such as Brasso or Weiman. Apply a small amount of the polish to a soft cloth and rub the tube in a circular motion, applying moderate pressure. This will remove any remaining scratches and produce a high-gloss finish.
6. Mount each lens to opposite ends of the tube
Create a lens cell to hold the objective lens securely in place. Attach this lens cell to the front end of the telescope tube using a strong adhesive like epoxy, ensuring the lens cell is centered and perpendicular to the tube. Insert the objective lens into the lens cell, ensuring it is securely seated and aligned properly. The objective lens should have a diameter of 60 mm to 100 mm, and it should be positioned at a distance of 1.5 to 2 times its focal length from the eyepiece lens.
Design an eyepiece holder to secure the eyepiece lens. Attach the eyepiece holder to the opposite end of the telescope tube using strong adhesive like epoxy, ensuring the holder is centered and perpendicular to the tube. Insert the eyepiece lens into the eyepiece holder, ensuring it is securely seated and aligned properly. The eyepiece lens should have a focal length of 10 mm to 30 mm, and it should be positioned at a distance of 10-15 mm from the observer’s eye.
Before attaching the lenses, ensure the telescope tube is clean and dry. Use lens mounts or retaining rings to secure both the objective and eyepiece lenses, ensuring both lenses are centered and seated properly. Make necessary adjustments for alignment and focus to ensure the optical axes are parallel and coincident. This careful alignment and adjustment is critical for the telescope to function properly and provide clear, focused images.
7. Build a focusing mechanism for the smaller lens tube
There are three primary types of focusing mechanisms: helical, rack-and-pinion, and sliding tube. For refractor telescopes, a helical focusing mechanism is often preferred due to its smooth operation and accuracy.
Calculate the thread pitch. The thread pitch is the distance between two consecutive threads on the helical focusing mechanism. A typical thread pitch for a refractor telescope ranges between 1-2 mm per turn. For instance, you might assume a thread pitch of 1.5 mm.
Create the helical thread on the lens tube. This can be done using a lathe or a thread-cutting tool. The major diameter of the thread should be approximately 20-25 mm, depending on the diameter of the lens tube. The thread length should be about 50-60 mm to provide a sufficient focusing range.
Assemble the drawtube, which is the moving part of the focusing mechanism. The drawtube should have an inner diameter larger than the outer diameter of the lens tube. Attach a corresponding thread to the drawtube, ensuring it matches the thread pitch calculated earlier.
Add a focusing knob. This knob will rotate the drawtube, allowing you to adjust the focus of your refractor telescope. Attach the knob to the drawtube using a screw or a bolt, ensuring it is comfortable to grip and rotates smoothly.
Assemble the focusing mechanism by attaching the lens tube to the drawtube. Make sure the threads are properly aligned and the lens tube moves smoothly along the drawtube when the focusing knob is rotated.
8. Use rack and pinion gears or a simpler friction fit that allows sliding the tube in and out
Attach the rack, a toothed bar, to the telescope tube, and connect the pinion gear, a small gear, to the adjustment knob. Ensure proper alignment between the pinion gear and the rack.
Operating this system is straightforward; simply rotate the adjustment knob. As the pinion gear turns, it engages with the rack, causing it to move linearly. This linear motion adjusts the telescope tube’s position, allowing you to achieve the desired focus. The gear ratio determines the number of rotations needed for adjustment, providing a smooth and precise experience.
9. Paint the inside of the tubes black to minimize internal reflections
Paint the inside of the telescope tubes with a flat, non-reflective black finish. Use a matte black paint with low reflectivity (2-3% or less) to minimize scattered light reaching the eyepiece or detector. Specialized paints like Krylon Ultra-Flat Black or Rust-Oleum Flat Black are recommended for optimal results. If you’re using a plastic tube, such as a PVC pipe, choose paints specifically designed for plastics, like Krylon Fusion or Rust-Oleum Plastic Paint.
Apply multiple thin coats, allowing each coat to dry completely before applying the next. Use a soft brush or foam applicator to apply the paint evenly, working from the center outwards to prevent streaks and bubbles. Avoid using glossy or reflective paints, as they can exacerbate internal reflections.
Consider additional techniques like using flat black paint on sandpaper for a rough texture or lining the tube with non-reflective materials like felt or flocking. Internal baffles along the tube can help reduce stray reflections. Properly controlling internal reflections is an important aspect of telescope design, as it maximizes contrast and image quality, especially for faint astronomical objects against dark skies.
10. Build a stable tripod to hold your telescope for steadier viewing
Gather the necessary materials. You will need three wooden or aluminum legs with a diameter of 1.5 to 2 inches and a length of 30 to 40 inches. Obtain a wooden or aluminum tripod head with a diameter of 6 to 8 inches and a thickness of 1 to 2 inches. A center column with a diameter of 1 to 2 inches and a length of 10 to 20 inches is required. To secure the legs, you will need three leg locks, such as wingnuts or quick-release clamps. A tripod adapter (1/4″-20 or 3/8″-16 screw) is necessary to attach the telescope to the tripod.
Each leg should be sturdy enough to support the weight of the telescope, with a minimum diameter of 1.5 inches. The tripod head should securely hold the telescope and provide a stable platform, with a diameter of 6 to 8 inches. The center column should be sturdy and capable of supporting the telescope’s weight, with a diameter of 1 to 2 inches. For maximum stability, angle the legs at approximately 60 to 70 degrees. Ensure the telescope’s weight is evenly distributed across the tripod legs.
To assemble the tripod, start by attaching the legs. If using wooden legs, glue and screw them together. For aluminum legs, attach the leg locks. Next, secure the tripod head to the top of the center column using screws or bolts. Attach the center column to the tripod head, ensuring it is securely fastened. Attach the legs to the tripod head, making sure they are evenly spaced and securely fastened. Attach the tripod adapter to the top of the tripod head.
How to make a simple refractor telescope?
To make a simple refractor telescope, follow these 7 steps.
- Prepare two convex lenses with different focal lengths (a larger and a smaller one)
- Prepare two cardboard tubes (towel paper rolls or mailing tubes)
- Use the larger tube for the main body of the telescope
- Attach one lens (the larger one) to one end of the tube securely using tape
- Slide the smaller lens inside the smaller diameter tube
- Slide smaller tube into the bigger to make the telescope
- Point the larger lens end towards the object you want to observe
- Slide the smaller lens (or the entire smaller tube) in and out to focus the homemade telescope
1. Pepare two convex lenses with different focal lengths (a larger and a smaller one)
The first lens to consider is the objective lens. This lens should be a convex lens with a longer focal length, ranging between 500-1000 mm. The longer focal length provides a larger image, thereby enhancing the view of far-off celestial bodies. It’s crucial to ensure that the diameter of the objective lens is at least one-third to one-half of its focal length to minimize vignetting.
The second lens is the eyepiece lens, which is a convex lens but with a shorter focal length, between 20-50 mm. This lens is responsible for magnifying the image formed by the objective lens. The diameter of the eyepiece lens should be appropriately chosen to avoid vignetting, which can limit the field of view.
When selecting the lenses, it’s preferable to employ achromatic lenses. These lenses minimize chromatic aberration, a common issue that can lead to color fringing in the observed image. Materials like glass or plastic with a high refractive index, such as BK7 or acrylic, are suitable for making these lenses.
2. Prepare two cardboard tubes (towel paper rolls or mailing tubes)
Obtain two cardboard tubes of different diameters. A toilet paper roll and a paper towel roll serve this purpose well. Ensure that the toilet paper roll, which will function as the eyepiece tube, has a diameter of about 4-5 cm, while the paper towel roll, acting as the main tube, should have a diameter of approximately 7-8 cm.
Cut the tubes to the desired length. The toilet paper roll should be trimmed to a length of 10-12 cm, while the paper towel roll should be around 20-25 cm long. This will provide a comfortable viewing distance and sufficient space for the lenses.
Cut out two circular pieces from cardboard or foam board, ensuring that their diameter is larger than that of the lenses. These mounts will securely hold the convex lenses in place.
Cut two small rectangular slots near the ends of each tube. These slots should be wider than the lens diameter, around 2-3 cm. This will allow the lenses to fit snugly into the tubes without causing any damage.
3. Use the larger tube for the main body of the telescope
Select a large, sturdy cardboard tube to serve as the main body of your telescope. You can use a paper towel roll or a toilet paper roll, depending on the desired size of your telescope. The ideal dimensions for the tube are an inner diameter of 6-8 inches (15-20 cm) and a length of 24-36 inches (60-90 cm).
Construct a lens holder by cutting a small cardboard or paper ring that fits snugly inside the tube. Position the ring about 2-3 inches (5-7.5 cm) from the top of the tube. Secure the ring with glue or tape to hold the lenses in place.
Assemble the lenses by placing the objective lens at the top of the tube and securing it to the cardboard ring using glue or tape. Then, attach the eyepiece lens to the bottom of the tube, ensuring it is centered and secure.
4. Attach one lens (the larger one) to one end of the tube securely using tape
Apply a thin, even layer of tape to the cardboard. You can use duct tape or packing tape for this purpose. Make sure to cover the entire surface, as this will prevent the lens from shifting during use. Once the cardboard is ready, carefully position the larger lens onto the taped cardboard. Ensure that the lens is centered and even to achieve the best results.
Apply the tape around the edges of the lens, making sure it is not too tight, as this could cause damage to the lens or the tube. The tape should be just tight enough to hold the lens in place securely.
Check the lens for any movement or shifting. If the lens moves, add more tape as necessary to ensure a secure fit. Following these instructions will help you create a stable and functional telescope that children and adults can enjoy using to explore the world around them.
5. Slide the smaller lens inside the smaller diameter tube
Carefully place the eyepiece lens into the smaller diameter tube. Ensure it is centered and even, with the curved surface of the eyepiece lens facing the objective lens. Precision is key in this step to achieve a well-focused telescope.
Once the eyepiece lens is aligned, gently push it into the tube until it is seated snugly. You can use a small amount of optical adhesive or a retaining ring to hold the eyepiece lens in place. Be cautious not to apply too much pressure if you’re using a retaining ring, as it can cause the lens to become misshapen or break.
Focus your telescope. Hold the telescope tube vertically and look through the eyepiece lens. Adjust the position of the eyepiece lens within the tube until the image is focused and clear. You may need to rotate the eyepiece lens to achieve optimal focus.
6. Slide smaller tube into the bigger to make the telescope
Align the tubes by holding the smaller tube and larger tube parallel to each other. Ensure their optical axes are aligned as this is crucial for proper image formation and to avoid any obstruction or vignetting. This step is essential to make your telescope function correctly.
Verify the correct orientation of the smaller tube and carefully insert it into the larger tube. Ensure it is fully seated and even with the larger tube’s receiving end. Apply gentle pressure and twist the smaller tube back and forth to ensure a smooth, secure fit. Be cautious during this step as it determines the optical performance of your homemade telescope.
6. Point the larger lens end towards the object you want to observe
Locate the object you’re interested in observing. Once you’ve aimed the objective lens, you can then fine-tune its position by looking through the eyepiece. This involves making small adjustments to the telescope’s small tube until the object is centered and in focus. It’s important to handle the objective lens with care during this process as it is a sensitive and critical component of the telescope.
7. Slide the smaller lens (or the entire smaller tube) in and out to focus the homemade telescope
Focus on a distant object, such as a star, a bright planet, or the Moon. Look through the eyepiece and slowly move the eyepiece holder or drawtube towards or away from the objective lens. Observe the image through the eyepiece as you make these adjustments; it will become sharper or blurrier depending on the distance between the lenses.
Stop adjusting the eyepiece holder or drawtube when the image appears focused and clear. The ideal distance between the lenses, known as the back focal length, ranges from 10 to 20 inches (25 to 50 cm) for a refractor telescope. To fine-tune the focus, make small, incremental adjustments to the distance between the lenses.
How to make a simple reflecting telescope?
The primary component of reflecting DIY telescope is the primary mirror, which is a larger concave mirror, preferably parabolic in shape. An 8-inch diameter is commonly used for the primary mirror. To create the mirror cell or holder, mark and cut a circular disc from cardboard, ensuring it matches the primary mirror’s diameter. This disc is then used to make the mirror cell, which is securely attached to the end of the telescope tube.
The secondary mirror is a smaller flat mirror that reflects light from the primary mirror to the eyepiece. It is positioned at a 45-degree angle to the primary mirror. This arrangement allows the light gathered by the primary mirror to be directed out to the side of the tube where the eyepiece is located.
A sturdy mount is necessary to hold the telescope tube. This can be a tripod or a wooden or metal base. The mount should allow for smooth altitude and azimuth adjustments, enabling easy directional changes for viewing different celestial objects.
Precise alignment and collimation of the mirrors are required to ensure the telescope functions properly. This step involves adjusting the mirrors so that they are correctly aligned with each other and with the eyepiece.
Simple materials like cardboard tubes, lenses, and mirrors, along with basic tools, are all that is needed to make a reflecting telescope. The assembly process involves attaching the primary mirror, secondary mirror, eyepiece, and tube together, following the classic Newtonian reflector design.
