8" mirrors

[The Warthog]

"Yeah marking the chip out with matt black paint or even a black permanent marker will sort it out.

If you replace the mirror, at f5 I would definitely go with a well figured parabolic mirror.

There's a lot of reasonably priced 8" parabolic mirrors available in the US - check http://search.ebay.com/parabolic-mirror_W0QQfclZ4QQfnuZ1

Even with shipping, they'll come in under £70

Andy"

I checked out these mirrors, and they are said to be parabolic, and are f3.75, which, it seems to me, would make a pretty ridiculous telescope for anything but widefield observing at low power. The scope would look like an ice-cream tub. I shopped around previously, and the best I can some up with on an 8" f/5 or f/6 mirror is about CDN$160. By the time you acquire most of the parts, it costs more to make one than to buy one. I've thought about building one, but no matter how I plan it out, I'm either going to pay more than I pay for a reasonably well-made skywatcher, or spend the rest of my life collimating the homemade mirror cell and diagonal. Either way, I will wish I'd just bought a scope.

There are no better mirrors available on eBay at the moment.

Does anyone save money on home-building, short of grinding your own mirror and being a workshop genius? Even if you don't save money, can you beat the tailor-made quality?

[GazOC]

I'm a clumsey git, if I tried to make a scope I'd be chopping fingers off left, right and centre!!!

[Astroman]

Does anyone save money on home-building, short of grinding your own mirror and being a workshop genius? Even if you don't save money, can you beat the tailor-made quality?

Technically, I shouldn't answer this one, since I've ground mirrors and happen to be a workshop genius, but ...

>on soapbox<

"Saving" money depends on how you look at it. A hand made mirror will easily exceed the quality of an "off-the-shelf" one. I've yet to see a hand made mirror with >less< than 1/15 wave quality, whereas a typical off-the-shelf will test out at 1/8. More typical hand grounds are better than 1/20 wave, and that's usually by an average glass pusher. If you can find a well made, built to last telescope with 1/20 wave optics for what you'd pay to build one. let me know. I'll buy one. Sure, store bought scopes are convenient and do a reasonable job at viewing the faint fuzzies, but I'll take a hand mirror any day of the week. If the name in the glass is Spooner, Coulter, Schwarr, Lind or a few others, count me in. Just who the heck IS Meade or Celestron or Orion?

>Off soapbox<

[FLO]

How much wavefront can the eye appreciate Astroman?

Steve

[Astroman]

You can tell the difference between an 1/8 wave and a 1/20 wave of the same size on the same object, trust me. Not sure much after that, though. It's the same with EP's, too. Easy to see the diff between a Kellner and Plossl and Nagler.

But you know what? The "best" telescope for any given person is the one they use, regardless of any other factor. If you're happy with it, more power to ya! 8)