Is building your own reflector telescope worth it? I have always fancied building my own reflector telescope. I am wondering - For a certain budget, can you get better results with a home made rig? Or is this a folly, and really it would be better to buy a ready made unit?
 A: Fifty years ago, it used to be very common for people to make their own telescopes. Nowadays it has become very rare, because commercial telescopes have become relatively inexpensive. One result of this is that it is very hard to find the parts needed to build your own scope. Unless you have a very strong motivation to learn how to do this, and to track down the parts needed, I wouldn't recommend building your own scope. Because the parts are hard to find, they are very expensive, and a home made telescope will cost many times more than a commercially built telescope. Labour is so much cheaper in China where almost all telescopes are made nowadays.
http://www.atmsite.org/
http://stellafane.org/tm/atm/index.html
http://www.atmpage.com/
A: Building your own scope is a challenge, a labour of love and, when completed, a source of great pride. As has already been mentioned, you can design your own telescope . The making of the parts is challenging. I bought my own lathe in 1975. It has since been replaced by a Chinese model with an integrated milling machine. This machine is wonderful for the manufacture your own focusers and drive units. Electronics comes into the design and building of stepper motor drives. By the time you have built a few scopes you will have increased your knowledge in optics, engineering and electronics. The best thing about telescope making today is that  the internet has an almost limitless supply of information in all aspects of telescope making. Go for it!
A: (Assuming you're in the US)
It's hard to compete with the Chinese "econo-dobs" on price. A 150 ... 200 mm (6" ... 8") GSO-made dob (sold rebranded by the various companies here) is $300 ... 350. Could you build a dob for less than that? Umm... mmmmaybe?... But you'll have to be pretty persistent in hunting down the best deals for materials and stuff. Even so, quality-wise, it might be better in some regards, but worse in other ways.
You'll also need some tools for wood-working and such - if you don't have those to begin with, you'll probably blow the budget.
Also keep in mind that the cheap Corning-made Pyrex is all but gone (I should know, I bought one of the last 12.5" Pyrex blanks at the old price a few months ago), so you'll probably pay a little bit more for the mirror kit than last year - you'll probably be using Schott Supremax (borosilicate), which is the same thing, but being imported from EU, what with the exchange parity and overseas shipping, it's more expensive.
Maybe the chinese will pick up the slack and start making cheap borosilicate. Or maybe you find an old Pyrex blank real cheap, with some minor defect, that just requires muscle power and patience to fix. Maybe.
Update 2018/05: Borosilicate blanks are now available from various manufacturers at relatively affordable prices. Example of vendor:
http://firsthanddiscovery.com/astronomy/telescope-making.html
Or just use plate glass instead of borosilicate. It will take more time to cool down when in use, and there's a higher risk it will crack when you're pressing the hot pitch lap for polishing. But it's dirt cheap. Try and use annealed glass, though, not just any chunk of green transparent stuff you found laying on a pile of trash outside.
Why don't you do what I did? Forget about beating GSO on price. This is a long-term project anyway (unless you're unemployed and can work on it full time). You're not going to spend the money all at once. Then just be frugal, but try and do a good job at each step. In the end it will be more expensive, but chances are it's going to be better than the econo-dob from China.
Especially if you go slowly with the mirror. "In the optics lab, nothing good happens quickly". So go slowly, overdo each step a little bit, polish until all pits are gone, be patient and do lots of attempts when parabolizing, and you'll end up with an awesome primary mirror. Most econodobs are λ/4 at best; you could do a λ/10 or better, which will make a difference visually.
Plus, you can custom-design it - use a slightly larger secondary mirror so you could do some astrophoto with a DSLR on bright non-tracking targets like the Moon. Etc, etc.
Finally, you'll take pride in the result of your work. Anyone with money can buy a scope, but it takes patience and skill to make one from scratch. You'll also learn a lot in the process.
Good luck.
EDIT: I've heard of a guy who, while broke and unemployed, built a 16" truss dob. You can be sure he built it real cheap. So, yes, it's possible to beat the chinese on price. It's just not easy. Depends on what motivates you.
A: I started building reflectors in the 1950s and apart from being a labour of love it provides great satisfaction. In these days I polished my mirrors with jewlers rouge, that red stuff ! After making half a dozen scopes or so finished up making a 6"schmit-cassegrain which took me all of 8 years off and on..Still got that one.I'm sure its not 1/4 wave but it produces awesome images!!  So I wonder how you got on with your project...Writing from Scotland where viewing is limited by weather..Anyway good luck !!
