Jay, it is possible but technicall difficult. All of the wavefronts from the constiuent mirrors must coincide to 1/4 wave, just like a monolithic mirror. The James Webb is an infrared telescope, meaning it operates at longer wavelengths than a visual telescope. The diffraction-limited tolerance is thus more lax for those mirrors, than for a visual telescope. Modern multi-mirror professional telescopes use active control of each individual segment to keep them all in-step. You'd need a similar arrangement for an amateur scope, just on a smaller scale. A multi-mirror telescope is essentially an interferometer. You end up with the resolution of the diameter of the array, with the light-gathering power of the sum of the individual elements. But keeping all of the individual surfaces in-place at a level of precision equal to a single surface is a daunting task. It would be easier, cheaper, and yield better results to just make a 36" telescope, in this instance. Good question, though! It's been one of the amateur's dreams for a century. On 8/26/15, Jay inUT <jayleads@gmail.com> wrote:
Ok, I got approached by my boss at work about the possibility of making a 36" mirror for observing from say several 8 inch mirrors (think an arrangement like James Webb). In thinking about this to me it seems that there are issues here about positioning the mirrors and ensuring that once ground, they form a parabola etc. So what are the thoughts on this? Can an amateur make a large mirror from smaller mirrors and what would it take? Just curious and I know what my reply was but I said I would inquire.