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

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SUMMARY

The discussion centers on the construction of a Newtonian telescope using a concave mirror with a focal length of 2 meters. Participants suggest using a flashlight and paper to locate the focal point and emphasize the importance of placing the secondary mirror correctly, either before or after the focus. The optimal material for the telescope tube is identified as thin plastic, which effectively blocks extraneous light while remaining lightweight. The conversation highlights practical advice for amateur telescope builders.

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  • Understanding of Newtonian telescope design
  • Knowledge of focal lengths and mirror placement
  • Basic skills in DIY construction techniques
  • Familiarity with materials suitable for telescope tubes
NEXT STEPS
  • Research the principles of Newtonian telescope optics
  • Learn how to calculate focal points for concave mirrors
  • Explore materials for building lightweight telescope tubes
  • Investigate methods for minimizing light interference in telescopes
USEFUL FOR

Amateur astronomers, DIY telescope builders, and hobbyists interested in optics and telescope construction.

Abd Errahmane
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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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Any replay
 
any replay
 
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.
 
thank you russ watters
 
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?
 
Probably a telescope mirror, 60cm f3.5 would make a reasonable Dobsonian cheaply.
 
can you help me in the tube of telescope , can it be by plastique or keybord or fe
 
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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