Parabola for 18 aluminum mirror

AI Thread Summary
To machine an 18" diameter, 1.5" high aluminum disc for a telescope mirror, the focal length is crucial, with a specified focal length of 79.2" and an f/4.4 ratio. The discussion involves configuring inputs for a CNC lathe, requiring precise calculations for the parabola formula to ensure accurate cutting. The material to be removed is 32.53 cubic inches, necessitating careful plotting of points along the 'x' axis to determine the perimeter from the center and the corresponding depth on the 'y' axis. Participants seek guidance on how to input these parameters into an AutoCAD program for effective machining. Accurate configuration is essential for achieving the desired parabolic shape for optimal telescope performance.
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Parabola for 18" aluminum mirror

Help; need to configure inputs into parabola formula to machine an 18" dia., 1.5"h aluminum disc. for use as primary objective mirror in telescope.
 
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Depends on the focal length. At f10 it little matters. What focal length do you have in mind?
 


Focal length 79.2", 0.256 in. @ apex; f/4.4

Using a CNC lathe but need inputs for autocad program to 'run' lathe for accurate cutting. Removing 32.53 cu. in. material.

Not sure what to plot for points along 'x' to perimeter from center, depth of 'y'
 
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