Help with lenses for hand-made telescope

AI Thread Summary
When constructing a handmade telescope, using two lenses that are convex on one side and concave on the other does not create a true double convex lens unless the space between them is filled with glass. The user noted that viewing the moon made it appear smaller, indicating a negative focal distance. Meniscus lenses can be utilized effectively, but their orientation affects optical aberrations. It's crucial to consider the focal lengths of the lenses to ensure proper functionality. Understanding these factors is essential for successful telescope construction.
Mohab
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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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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).
 
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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.
 
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?
 
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