Build A Simple Galilean Refracting Telescope In 500 Rupees

Today I am going tell you the way how can you build a simple Galilean Refractor Telescope in just about 500 Pakistani Rupees. I think building this telescope must not take more than half hour of your’s and after this, you will be able to observe the moon and its craters and few double stars too.

So,

First, a little briefing about the design might help.

This telescope design was introduced by Galileo. Basically it works on the principle of refraction of light rays.

Light rays bend as they enter from one medium to another. In this way the light rays are brought to focus in the Galilean Refractor model.

Refracting Telescope Illustrated

Light from the primary convex lens is brought to focus at a certain point. At that point an eyepiece is placed to view the image.

Refracting Telescope Illustrated

Refracting Telescope from Cincinnati Observatory in 1848

Now I will move on to the parts list and some mathematics.

I am not sure about the cost of the parts but it shall be near to the ones I mention here.

Parts:

• A plano-convex lens of +2 diopters with diameter of 2 inches. (Rs. 100)
• A microscopic eyepiece of 10x power. (Rs. 320)
• A PVC pipe of 2 inches diameter and of half meter length. (Rs. 50)
• A PVC pipe of 1 inch diameter and of 6 inches length. (Rs. 20)

Total = 490 (Prices subject to change from city to city)

Additional Supplies Needed:

• Black Electrical Tape.
• Old Newspapers.
• Scissors.
• A powerful glue.

Calculations:

Lets calculate the Focal Length of the convex lens.

Since,

Focal Length = 1 / diopter

Focal Length = 1 / 2

Focal Length = 0.5 Meters.

This means that the plano-convex lens you just purchased has a focal length of 0.5 Meters (500 millimeters)

The 10x microscopic eyepiece has a focal length of 25 millimeters.

Now we will calculate the magnification of this telescope.

Since,

Magnification = Focal Length of Objective / Focal Length of Eyepiece.

Magnification = 500 / 25

Magnification = 20x

Construction:

• From that half meter PVC pipe, cut 3 inch piece away.
• Join the Plano-Convex lens at one side of the tube opening with the help of glue (the convex side should be facing outside).

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  Fixed Lens at one end of the tube.

• Let it dry and make sure its firmly attached.
• Wrap the 1 inch diameter PVC pipe with newspapers well, so it can slide inside and outside the main tube also known as Objective Tube.

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  PVC pipe wrapped in magazine.

• Fix the eyepiece in one side of that little tube also known as the Draw Tube.

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  Eyepiece in Draw Tube

• Your telescope is ready.

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  My 40x Telescope

Enjoy the moon viewing, or other terrestrial objects.

Be Advised:

NEVER EVER TRY TO LOOK AT THE SUN WITH ANY LENS AND ESPECIALLY A TELESCOPE. IRREVERSIBLE DAMAGE TO YOUR EYES WILL OCCUR WITHIN MICROSECONDS.

Notes:

• The Refractor Model shows erect images only when you have a negative power eyepiece (Galilean Mode). In this telescope you are using a positive eyepiece. So this design is called Keplerian Mode. You will see everything upside down.
• This isn’t a Solar Telescope, avoid sun viewing.
• This telescope has a magnification of 20x. You will see everything 20 times bigger than its original size.
• While viewing moon and other distant objects, you will have to move the draw tube inside the main tube until the image is sharp and clear.
• If you are viewing nearer objects, you will have to pull out the draw tube a little or more until the image is focused.

Troubleshooting and Help:

If you are having any problem in the construction of this telescope or have any other questions, feel free to ask. I am always ready to help.

Acknowledgements:

If today I am able to write this tutorial, its just because of the great help offered to me by Mr. Tom Pope, Mr. Jim Mosher and Mr. Ali Khan. Without their help, I would have never been able to build a telescope and write this simplified tutorial for beginners. Thank You All.

Wish You Clear and Dark Skies.