Concave mirror telescope

  • Stargazing
  • Thread starter Abd Errahmane
  • Start date
  • #1
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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Answers and Replies

  • #4
russ_watters
Mentor
19,926
6,392
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.
 
  • #6
4,662
5
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
mgb_phys
Science Advisor
Homework Helper
7,774
13
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
HallsofIvy
Science Advisor
Homework Helper
41,833
956
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.
 

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