Where should the secondary mirror be placed in a concave mirror telescope?

In summary, the conversation is about a person who found a concave mirror telescope in their town and wants to use it to make a Newton telescope. They are unsure about the location of the focus and secondary mirror, and are seeking advice. Another person suggests using a flashlight and paper to find the focal point, and mentions buying a large concave mirror for a cheap Dobsonian telescope. They also offer advice on building the telescope tube.
  • #1
Abd Errahmane
11
0
hello,

I found a concave mirror telescope in my town
I think that it is very good for making Newton telescope
Estimated length of 20 cm
I will make a telescope , but I have a problem , I do not know the place of the focus
and the place of secondery mirror; after focus or before

can you help me please!
 
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  • #2
Any replay
 
  • #3
any replay
 
  • #4
Point a flashlight at it and use a piece of paper to find the focal point, then do the math to find the focal point for infinity.
 
  • #5
thank you russ watters
 
  • #6
I have a chunk of glass I bought at a garage sale for $3.00. It is 22" diameter and 2" thick, and is concave on one side (I didn't know this until I took it home and cleaned it off). It has a focal length of 2 meters, and is unsilvered. I have been using it as a small coffee table since about 1970. What was the mirror for?
 
  • #7
Probably a telescope mirror, 60cm f3.5 would make a reasonable Dobsonian cheaply.
 
  • #8
can you help me in the tube of telescope , can it be by plastique or keybord or fe
 
  • #9
Whatever will keep out extraneous light and is not heavy. Probably a thin plastic tube would be best. Use whatever you like to reinforce it and support it from the outside.
 

1. What is a concave mirror telescope?

A concave mirror telescope is a type of telescope that uses a curved mirror to gather and focus light from distant objects. It is also known as a reflecting telescope because it reflects light instead of using lenses to refract it.

2. How does a concave mirror telescope work?

A concave mirror telescope works by gathering light from a distant object and reflecting it onto a focal point. The mirror is curved in a way that causes the light rays to converge at the focal point, creating a magnified image for the viewer to see.

3. What are the advantages of using a concave mirror telescope?

One advantage of using a concave mirror telescope is that it does not suffer from chromatic aberration, which is a distortion of colors that can occur in refracting telescopes. It also has a wider field of view and allows for larger apertures, resulting in brighter and clearer images.

4. What are the limitations of a concave mirror telescope?

One limitation of a concave mirror telescope is that it can suffer from spherical aberration, which is a distortion of the image caused by the shape of the mirror. This can be corrected by using a parabolic mirror instead of a spherical one. Additionally, concave mirror telescopes can be larger and more difficult to transport and set up compared to refracting telescopes.

5. How is a concave mirror telescope different from a refracting telescope?

A concave mirror telescope uses a curved mirror to gather and focus light, while a refracting telescope uses lenses. This results in different optical properties and advantages for each type of telescope. For example, a refracting telescope may have a clearer image, but a concave mirror telescope can have a wider field of view and a larger aperture.

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