8 inch mirror being ground.

Why don't we have a mirror grinding party when it's too cloudy for a star party
Bill H.

i remember about 10 years ago liam smyth i think it was in the IAS gave a series of classess where you brought your own mirror along for instruction on grinding it.
stephen.

A great book I have at home which goes into detail how to build a telescope from mirror to mount to eyepiece is Handbook for Telescope Making, by Neale E. Howard. Its an old book, but at the time, it used materials readily avalable to the amateur astronomer/mirror grinder. I recommend it highly if anyone would like to think about getting their fingers wet and full of carborundum and emery!

Seanie.

I'll just do a general reply rather than reply to individuals.

Well since I just bought a nice shiny new Canon EOS 300D, you can be sure I'll be keeping a photographic record:) I have been making notes as I've been plodding along so I'll start a thread here and post is as a kind of blog.

Dave L. Doing a bigger mirror is no more difficult per-se, the technique is pretty much the same, except you would probably use a sub-diameter tool. The hard part is moving all that glass around. After a few nights grinding an 8 inch i'm already getting sore hands. I feel like I might have pulled a tendon or something in the upper part of my hand. Maybe some kind of RSI. Maybe its just me using muscles that I never used before! Anyway the pain is gone so I'll start back tomorrow night.

Grinding to a particular wavelenght is just more time consuming than difficult. The real difficulty is in testing for accuracies that small. Most serious mirror makers start looking at interferometry tests when they get down to that accuracy. The thing is, I dont see anypoint in going beyond, say, 1/10 wave really. The diffraction limit is reached at 1/8 wave, so the sky is gonna introduce more distortion than any surface error of less magnitude than 1/8 - 1/10 wave anyway.

You know mirror grinding parties are big in the US, If there were a few interested I'm sure we could get together and do something like this. Phil Lardner who posts on this board sometimes is really expert at this kind of thing. Perhaps we could rope him in as our mentor!!

LOL @ Bill_H: This is my first mirror, lets see how this goes before we start talking about classes!!! ANyway Phil Lardner is much more eminintly qualified.

Wally: When this is done and working, I'd be happy to take it along to the SDAS and give a lil talk about the process. That goes for any of your clubs too.

Seanie: Richard Berry also has a great book on the whole ATM thing including mirror making, however Texereau is still the king of books IMHO. There is also a tonne of stuff around the net. Particulary good is this.

www.stellafane.com/atm/atm_main.htm

ATM is such fun, there is so much seriously cool gear available for you to make rather than shelling out thousands on shop bought scopes. Up to now I've built all of my telescopes with purchased optics. This is my first toe in the 'optical fabrication' waters. We'll see how it goes.

I have to say that up until now, I thought that anyone actually grinding their own mirror was crazy,
I had visions of it taking months to get it to the shape you want, but if you can do it in a weekend, that puts it in a whole new perspective.

You can save alot of money and make your own 16"scope and has a garenteed accuracy (since you make it), it suddenly sound very appealing !!
Its the testing part that worries me.

Is it really that much harder to make a good fast mirror or is it a mechanical limitation in the automation process in factories?

Is it really that much harder to make a good fast mirror or is it a mechanical limitation in the automation process in factories?

Dave faster mirrors are generally harder to make than their longer cousins. When you start to go beyond F/5 it starts to get difficult since the figure gets so pronounced, there is a lot more work to do, nevermind shifting all that glass. The figuring becomes mucho difficuklt and testing is harder too. If you wanted to make say a 16" f/4 you would have to start smaller and work your way up. I'd be confident that a 16" short focal lenght mirror as a starting point for a mirror making newbie would be a bad idea. Start with something like 8" F/6, theres enough in that to get you on the road, start working up in aperture staying around F/6 and then start shortening the focal lenghts if you wish.

If you look at someone who hand figures and sells mirrors commercially and see the difference in prices between longer an shorter focal lenghts you'll get an idea just how much more difficult it is.

BTW mirror making is not something you can do in a weekend unless you never eat or sleep! and 8" f/6 would take around 30 hours work probably longer to a newbie and quicker for a vet with all the testing kit set up.

BTW mirror making is not something you can do in a weekend unless you never eat or sleep! and 8" f/6 would take around 30 hours work probably longer to a newbie and quicker for a vet with all the testing kit set up.

maybe a bank holiday then
Seriously though, if you could do it in a week or 2 or 3, then suddenly its looking very viable, now, if only I had the time