Everyone likes to watch the stars and look at the moon in a clean night. But sometimes we want to see far away. We want to see it near. Then the humanity created the telescope!
we have many kinds of telescopes, including the classic refractor and the Newtonian reflector. Here, in Brazil - where I live - a telescope is a "luxury". It costs between R$1,500.00 (near US$ 170.00) and R$ 7,500.00 (US$ 2,500.00). It's easy to find a refractor by R$500,00, but it's near 5/8 of a salary, considering that we have a lot of poor families and young ones expecting for a better life's condition. I'm one of them. Then I found a way to watch the sky! Why don't we make our own telescope?
Another problem here, in Brazil, is that we have very little content about telescopes.
and lens are particularly expensive. So, we have no conditions to buy then. An easy way to make it is using things that aren't useful anymore!
But where to find this things? Easy! A reflector telescope is made of:
- A primary mirror (concave)
- A secondary mirror (plan)
- An optical lens (The hardest part!)
- An adjustable tube.
- A tripod;
Where to find these things?
- Concave mirrors are used in beauty salons (Makeup stores, barber, etc. );
- Plane mirrors are found in a lot of things. You just need to find a small mirror (near 4 cm²);
- Optical lens are hardier to find. You can get it from broken toys or make it by yourself. (I used an old 10X lens from a broken binoculars).
- You can use water pipes (something between 80 mm and 150 mm of diameter), but I'll use an empty ink tin and a towels tin.
- Some black spray.
need some PVC pipes, connectors and some cardboard rolls too.
You can use hot glue or silicon paste.
So, no more waiting! Let's get it started!
Step 1: Calculating Optical Components
I get a 140 mm diameter concave mirror with a Sagita of 3.18 mm (I measured with a caliper).
But first, you need to know what the mirror Sagitta is. It's the depth of the mirror (the distance between the lowest part of the surface and the height of the borders).
Knowing this, we have:
Mirror Radius (r) = D / 2 = 70 mm
Radius of Curvature (R) = r2 / 2s = 770.4 mm
Focal Length (F) = R / 2 = 385.2 mm
Focal Ratio (f) = F / D = 2.8
Now we know everything we need to make our telescope!
Step 2: Making the Main Tube
By a bizarre coincidence, our can of paint fits perfectly with the towels tin!
At first, we need to remove the paint on the can’s bottom.
Then we need to measure the distance between the concave mirror and the ocular spot. For this, we need to consider the radius of the can of paint.
Then we mark a height of 315 mm. It's near 30 cm.
At this height, we'll make a hole in the can, like in the photo. On this case, I made a hole near 1.4 inch to fit the PVC connector.
As you can see in the next photo, the mirror fits perfectly in the can.
Step 3: Assembling the Plane Mirror
I decided to fix the mirror's support using 3 points, like the drawing.
To fit the plane mirror, I used two wood sticks and a small wood triangle with 45°.
Then I made some measures. With a drill, I made the holes to insert the sticks.
Then I calculated the distance between the center of the mirror and the sticks' holes. It's 20 mm.
Make the holes in the can of paint, with a drill.
So I adjusted the sticks until the plane mirror, when observed by the ocular's hole, show my own eye.
*I attached the mirror in the support with hot glue.
Step 4: Focus Adjustments
I used a microphone pedestal as a tripod for the telescope. Fitted it with some tape and an elastic.
To find the focus, we need to aim the sun with the telescope. Obviously, NEVER LOOK AT THE SUN WITH A TELESCOPE!
Put a paper in front of the ocular hole and find the smaller light spot. Then measure the distance between the hole and the paper, as the figure. I've a distance of 6 cm.
This is the distance you need between the hole and the ocular. To fit the ocular, I used a cardboard roll (from a toilet paper), cutted and fixed with some scotch tape.
Step 5: Support & Outfit
An important detail:
Anything in the tube insides needs to be black. It prevents the light of reflecting in other directions.
I painted the ink tin outsides of black just for appearance. I putted some barrettes too, to hold better the towels tin in the ink tin.
Some other barretes to hold better the secondary mirror sticks... And then I fixed the "tripod PVC socket" with a rivet and hot glue.
I putted a golden plastic edge in the top of the ink tin, to make it beautiful.
Step 6: Tests and Final Considerations
I waited for the nightfall as a child waits for a Christmas gift. Then the night came, and I went outside to test my telescope. And this is the result:
As we know, it's so much difficult to take photos at the telescope.
But as you see, it's working!
A important book to help with this project was:
NICOLINI, Jean. "Manual do Astrônomo Amador". Papirus, 2 ed., 1991.
I need to wait for a moonlight, because we are in the new moon. Then I'll try to take a photo of the moon.
Thanks for the attention.
And I would like to thank my friend Julia for helping me with, more than everything, the text revisions. And sorry for my mistakes, I'm learning.