Help with lenses for hand-made telescope

In summary, the conversation discusses the process of making a handmade telescope using two lenses that are convex on one side and concave on the other. The individual realizes they need a double convex lens for both the object and eyepiece, so they attempt to combine the two lenses. However, this may not result in a double convex lens as the hollow space between the lenses is filled with air. The focal lengths of the lenses are also mentioned as a factor that could affect the performance of the telescope.
  • #1
Mohab
2
0
I'm trying to make a handmade telescope, but I'm stuck with the lenses I bought 2 lenses. they are the same
"convex from one side and concave from the other side" like glasses lenses.

then I knew that I need a double convex for both the object lens and the eyepiece lens.
so I decided to put the 2 lenses that I bought together to make a double convex lens so now air is in between the two lenses.

Is what I did going to give me a double convex lens?!
 
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  • #2
Hello Mohab, :welcome:

I'm afraid not. Unless you fill up the hollow space in beteen with glass too ...
Did you check if the two lenses have positive or negative focal distance ? (positive: they work as a magnifying glass, negative: things look smaller but stay upright).
 
  • Like
Likes Mohab
  • #3
Thanks for your reply BvU,

I've looked up to the moon with it, the moon appeared smaller, I think it has a negative focal distance.
 
  • #4
Mohab said:
I'm trying to make a handmade telescope, but I'm stuck with the lenses I bought 2 lenses. they are the same
"convex from one side and concave from the other side" like glasses lenses.

then I knew that I need a double convex for both the object lens and the eyepiece lens.
so I decided to put the 2 lenses that I bought together to make a double convex lens so now air is in between the two lenses.

Is what I did going to give me a double convex lens?!

meniscus lenses are fine to use; just be aware that the orientation does impact the total amount of aberrations.

What are the focal lengths of the lenses?
 

1. What types of lenses are suitable for a hand-made telescope?

The type of lenses suitable for a hand-made telescope depends on the specific design and purpose of the telescope. Generally, convex lenses are used for magnification, while concave lenses are used for correcting aberrations. It is important to choose high-quality lenses with good optical properties for optimal performance.

2. How do I determine the focal length of a lens for my telescope?

The focal length of a lens can be determined by measuring the distance from the center of the lens to the point where the image is formed. This can be done by projecting an object onto a screen and adjusting the distance between the object and the screen until a clear image is formed. Alternatively, you can use a lensometer to directly measure the focal length.

3. Can I use lenses from old cameras or binoculars for my telescope?

Yes, you can repurpose lenses from old cameras or binoculars for your telescope. However, it is important to note that these lenses may not have the same optical properties as lenses specifically designed for telescopes. It is recommended to test the lenses and make sure they are suitable for your telescope before using them.

4. How do I clean and maintain the lenses for my telescope?

To clean the lenses of your telescope, use a soft, lint-free cloth and a lens cleaning solution. Gently wipe the lenses in a circular motion, starting from the center and working your way out. Avoid using harsh chemicals or rubbing the lenses too vigorously, as this can damage the coating. Store the lenses in a protective case when not in use to prevent dust and scratches.

5. Do I need to use multiple lenses for my telescope?

It is not necessary to use multiple lenses for a hand-made telescope, but using a combination of lenses can improve the magnification and image quality. This is known as an eyepiece system and typically involves using a larger primary lens or mirror and a smaller eyepiece lens. Experimenting with different combinations of lenses can help you achieve your desired results.

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