Making your own mirror?

[Glasspusher]

 I don't think that it is for us to persuade you to get stuck in to making a mirror unless you are really keen to do it. There must be an awful lot of half-made mirrors lying in cupboards in the country where the initial enthusiasm has waned

.

Nigel, without doubt that is true. I am asking why are they half made? Amongst the reasons must be that the methods they were following were not user friendly. We both know how difficult it is to set up and use the Foucault knife edge test for the first time, it inevitably prompts the question, 'where do I put my eye?' 

It is said that we learn in different ways, anyone who has tried to make a mirror knows that to be shown what to do wins hands down. I applaud you and Rich for offering to help in this way. 

John

[mapstar]

I am in the process of doing a 22" and have found it an interesting project up to now.

It's quite helpful being near someone who has knowledge as well as interest in doing one them selves. I only live a half hour drive from crash test dummy so we took the project on together.

John has given hints and his seminar was the starting point so maybe a good place to start to attend one and find out a few things.

[Rustysplit]

I think you may be right about the foucault test as a stumbling block for some John. I also think that a general mish mash of ideas and techniques can knock your confidence. I know when I did mine last year, the more I read various testing guides and figuring guides, the more confused I became. In the end the solution was to follow one technique and stick to it. The Ronchi test is also very easy to understand and set up.

I remember reading tales of mirror grinding taking many tens of hours of hard repetitive toil, and this also makes people think twice i reckon. In reality, it does take time, but is quite manageable. I did not keep accurate records of how long I spent on my 14", but from conception to finished 'scope took 3 mnths. This included actually making the truss dob and getting the mirror coated.Most of the work was done in the eves and weekends too. I found that far from finding the grinding tedious, I actually had to force myself to stop working on the mirror.

[Peter Drew]

Not long after Newton proposed the reflecting principle for telescopes I took out a library book on mirror making. Despite reading it several times I still found it confusing (teenager). I eventually sent away for a 4" mirror making kit, it arrived with a small typwritten sheet which in so many words said just rub the pieces of glass together until you have a mirror. Sounded really easy at last and got me going, it's amazing how much better it is once you get hands on and the detailed description in the book gradually made more sense.   

[crashtestdummy]

For me doing the mirror making seminar with John got rid of a lot of the myths that I was worried about.seeing someone do something is much better than a thousand words written about the process

[Astrobits]

+1 for crashtest.

I think that the old written methods were off-putting, unfortunately oft repeated in newer instructions. I never read a book on mirror making before making my first mirror but I had a teacher whose wisdom originated, via others, from Jim Hysom of Astronomical Equipment. Having made that first 6" mirror I went on to make an 83mm flat for a 12" mirror I already had, and I took that flat to Horace Dall who tested it and pronounced it "not bad". I think that the problem is that there are too many ways to do a job described in the books and nothing other than direct advice from someone who has made mirrors will help getting round any problems.

I think, John, that most abandoned mirrors were started by people who were trying to do it alone. I think that as part of a group there is always encouragement to keep going.

Nigel

[mapstar]

+1 for crashtest.

I think that the old written methods were off-putting, unfortunately oft repeated in newer instructions. I never read a book on mirror making before making my first mirror but I had a teacher whose wisdom originated, via others, from Jim Hysom of Astronomical Equipment. Having made that first 6" mirror I went on to make an 83mm flat for a 12" mirror I already had, and I took that flat to Horace Dall who tested it and pronounced it "not bad". I think that the problem is that there are too many ways to do a job described in the books and nothing other than direct advice from someone who has made mirrors will help getting round any problems.

I think, John, that most abandoned mirrors were started by people who were trying to do it alone. I think that as part of a group there is always encouragement to keep going.

Nigel

Thats why me and Rich (crash) decided to do ours at the same time and keep the enthusiasm and momentum going by spurring each other on. To be fair the hogging out is laborious (boring but therapeutic) but when you see that massive deep curve generated (12mm on mine before the tile tool) it begins to be a thing of beauty created by your own hands. Building 3 scopes at once the smallest of which is 22" is also a challenge and extremely stressful but everyone needs help and the hogging isn't bad after that! 

[estwing]

I'd like to do one...but to be honest the one I've got is outstanding!

[mapstar]

I'd like to do one...but to be honest the one I've got is outstanding!

Yeah would've loved the chance to look at some objects with it Calvin but that peak cloud cover was a bit of a stumbling block!

Hope this year is gonna be better?

[starman345]

". I think that the problem is that there are too many ways to do a job described in the books and nothing other than direct advice from someone who has made mirrors will help getting round any problems.

Nigel, I think you hit the nail squarely on the head with that sentence. I am doing my first mirror at the moment, its a 10" pyrex that I would like to finish out to a f 6.4. I haven't seen a mirror made, just going by videos on YouTube( and they can be confusing, everyone seems to have their own particular stroke that they like) I have bought several books on mirror making, including Texereau, Ingalls and a couple of lesser known books. The are full of great information but it seems they all have their own way of doing the job. I read on another forum it might be best to just pick one book and go by that method and forget the rest. I envy you guys who have attended a mirror making seminar, or class

[JamesF]

I think once I have my obsy sorted out and get a few other jobs done I might look at making a few mirrors in increasing sizes and see how it goes.

I have this vague plan for some day having a large aperture dob sunk into a bit so I don't have to use a ladder to reach the eyepiece.  That's a way off yet though.

James