Quote: "They are so cheap these days, making one yourself makes no sense at all if you can buy one. I made a total of 5 in my younger and sillier days, but no more."
Well it depends if you want the rewarding experience of doing it yourself and learning a lot in the process. As stated, you made 5 mirrors already, so maybe you have done your time and had the reward, at least in some knowledge gained, and hopefully with the final result too. But others have never had a go, and no doubt, many of them don't want to either for various reasons.
These days, you have the choice, whereas years ago, there wasn't much of an option than to have a go yourself, if you wanted the chance of getting a decent optic. We are spoiled these days, with a choice of low cost and good performing optics, or high end precision, at a higher, but still very fair cost, when you consider how much time and effort go into fabrication, as well as the premium materials used, as Mark mentioned.
As far as differences between mass produced optics and premium "hand made" optics, despite the better quality of mass produced, there is definitely a difference between these and genuine premium optics, with all the usual qualifiers, such as good seeing conditions, collimation, thermal equilibrium, and excellent ancillary optical components such as secondary mirror and oculars.
Mark could elaborate further, but it's my understanding premium "hand made" doesn't necessarily literally mean glass pushed by hand, as far as I understand, even the premium opticians still uses machines for grinding and polishing, but perhaps using hands for final figuring. I imagine it would be very tiring pushing a piece of 2" thick and 20" diam. mirror by hand for hours on end, even though it can be done
I would think the "hand made" part is more to do with the skill, knowledge, extra care, quality of materials and substrate, extra time taken to polish carefully and the testing techniques used, as a basic guide,
Clear skies
Nick
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