Lens type for home-made experimental reflector telescope, and unknown camera lenses?


Well-Known Member
May 23, 2017
I'm doing some home experimentation with a fairly large (200mm) diameter concave parabolic cosmetic mirror, which the manufacturer claims is 'parabolic'.
My plan is to mount a small chrome-plated steel plate (compass mirror) at 45 degrees to the rear mirror (all in a matt black PVC tube), then mount an eyepiece on the side.
Until such time as I buy a proper 'scope, I want to try this home-brewed contraption out.
For the eye-piece (focal point?), I've tried a standard bi-convex magnifying lens, a plano-convex 20mmx8mm LED torch collimator lens, and barrel-type mini-lens from the webcam.
None of these produce an image.
Is the standard magnifying eyepiece in reflector telescopes a compound type?
I haven't yet tried directly onto a CCD image sensor (webcam or Canon DSLR without lens).
As my Canon is 'on the blink' at present, I tried a few 'macro' lenses in front of my cell phone.
The (HP or Yodata) webcam, which has a length of 12mm from rear coated lens to front concave lens, makes a great microscope!!
The magnification is so high, and DOF so shallow, that I had to steady the cell body top against the TFT screen surface of the PC monitor (hence parallax).
Shows individual RGB pixels on white area (200DPI monitor).
I guess the webcam uses a compound lens, but cell (Vodafone) lens unknown.
Webcam lens embossed with 4022-DT2 9
Regards, Clive2
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