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350 newt project


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from what I've read and gleaned, I believe starting with 6 or 8" is around the optimal size for a novice. Not sure it holds that larger mirrors are more forgiving.

For the smaller sizes, I think it's also probably a labour of love rather than a financial driver, although the cost benefits almost certainly increase with size (providing it turns out well, of course!).

I think that's about right. 6--8" was always the classical advice. You could probably be a bit more aggressive now because there is so much help and advice available on the interweb now. Generally the larger the mirror the harder it is (and more expensive), but the real driver is f/ratio (shorter f/ratio == harder mirror to make). Bigger mirrors certainly don't have easier tolerances! It also gets harder with very small mirrors, because they start getting fiddly to handle...

8-12" is probably a fair starting point these days.

Small mirrors cost you money to make (i.e. they'll be more expensive than buying the finished thing). The break-even point with home made mirrors is probably somewhere around the 12-14" mark these days; but most people don't do it to save money...

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I agree with TeaDwarf, if you have the apptitude a 12 inch is doable for a first mirror,

have a look at this thread if you have not seen it......http://stargazerslounge.com/diy-astronomer/113596-making-12-inch-mirror.html


Hi John

Thanks. Yes, I've been following your mirror making thread with great interest. Your explanations are really clear and a great inspiration for others (as is Paul's thread here).

Personally speaking, not sure I've got the confidence to tackle a project like this just yet, but have it on my list of things to do before I leave this mortal coil!


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You, Sir, excel at everything you've shown on this forum. :)

What a fantastic thread to read through.

You must be proud as punch.

The effort you've put in alone is astronomical. The heavens will reward you...I'm sure of it. ;)

Thanks very much that is very kind of you, the real test will be if this thing actually works.

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I really don’t like working with metal it seems impossible to cut it straight or square with hand tools. I was going to buy a spider from Protostar but the last I heard they were not even taking orders as they were so busy. So it looks like I am going to have to make my own.



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Hi Paul

You never fail to amaze regarding how quick you can fabricate stuff ! :) Looks good to me.

I'm looking forward to seeing how your mirror cell turns out. For my 6" I resorted to using wood and, although functional, was a bit Heath Robinson.

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Hi Kev it’s not actually fixed together yet it’s just sitting on the ply. I’ve still got the fun to come of chasing these bits of metal around the bench, drilling holes everywhere trying to fix it together and make it look something. The mirror cell will be the easy bit as that’s made from C/F.

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Paul, that spider looks good, I am sure it will turn out fine! Think of the money you are saving. I am really looking forward to your first images with the new scope.

Kev, it was Paul's thread on making his 14 inch that inspired me to produce a more detailed look at making a 12 inch mirror.


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