ATM suppliers in Australia

[richard3030 (Richard)]

Hi all,

I've fairly recently gotten involved in amateur astronomy, and I'm loving it. I've been doing some reading regarding telescope making, and I've come up with the brilliant idea of building a first telescope over the next couple of years as a present for my son (more sentimental than anything else - I know it would be way cheaper to buy something than build it).

I still have a lot of research to do, but can anyone recommend places in Australia which sell ATM supplies? e.g. mirror blanks

Cheers,
Richard.

[barx1963 (Malcolm)]

Bintel certainly sell mirror blanks see http://www.bintel.com.au/Accessories...3/catmenu.aspx
Other components, eg cells, spiders and secondary holders pretty much have to be sourced from OS. I have had some bits from Astrosystems in the States with no probs.

Malcolm

[scopemankit (Chris)]

Richard,

Before running to shops for telescope parts, consider looking through telescopes made on the internet and this includes the Iceinsoacae website.

The ingenuity and lateral thought applied to the hobby runs deep - some manufacturers never imagined their product would or could be used to build a telescope. Over the years, I have ground mirrors which were once porholes, glass table tops and even a glass dance floor from a hotel. Look around, steal with your eyes and you will be surprised at what you can do

Good luck,

[ZeroID (Brent)]

If you haven't ground a mirror before consider buying them ready to go. I built both my scopes but bought the mirrors and focusser. It saved a lot of time, I was up and going in about 4-5 months for the first build, mainly because I was learning the principles as I went. The second build was actually a rebuild of the first, much more complex Serrurier Truss design which took almost as long but was worth the effort.
I wouldn't have attempted either build probably without the help and advice I received on here and by buying the most complex and critical components I got a reasonable completion date. It was still an excellent engineering task that was very satisfying when it all came together.
My mirrors came from Bintel, original focusser was a second hand unit, since been upgraded twice ! There are plenty of ideas and assistance on here so trot out your ideas and thoughts and be prepared to modify them.

Good luck and have fun

Brent

[barx1963 (Malcolm)]

Sorry I wasn't reading properly that you were after mirror blanks rather than completed mirrors


Malcolm

[Satchmo]

Sydney Glass at Padstow should be able to cut 25mm plate glass blanks for you. Naxos Abrasives are a good source of abrasives and they sell cerium oxide too. You make a grinding tool from plaster and epoxy ceramic tiles to it for the grinding tool. I would recommend something like an 8" F7- F7.5 as a first scope. Its much easier to hold an 8" than a 6" .

[sopticals (Stephen)]

Originally Posted by Satchmo

Sydney Glass at Padstow should be able to cut 25mm plate glass blanks for you.

I would be hesitant on ordering the 25mm plate glass as supplied by Sydney Glass.

Some time ago,(if you search through the thread "Are there any amateur mirror makers alive in Oz/NZ" you will see an account of the reply I received from Sydney Glass concerning the quality of their 25mm plate glass at that time, and I would doubt that the current quality would be any different, unless they have changed their supplier.) I had requested them for the supply of the 25mm plate.

A shortened version of that post:

I received the following reply: "We have got some 25mm clear float, but it is "SO BADLY ANNEALED" it is impossible to cut conventionally. We use water jet and often supply panels of this to telescope enthusiasts".

When I asked for supply of a full sheet cut in quarters, the reply continued: " there is no point in providing you with stock glass because of "THE CUTTING PROBLEM" ".

It is ESSENTIAL that a mirror blank has at least a reasonable anneal if it is to be the building block for a successful mirror. I believe many a budding amateur mirror maker is discouraged by trying to fabricate a mirror out of a substandard substrate.

[Satchmo]

Hmm- the 30mm they used to sell was perfectly annealed...

Best way then is to use 19mm plate as everything I have looked at has been good.

[richard3030 (Richard)]

Thanks for all the advice guys. Is mirror making difficult? I realise it's an intricate and time-consuming process, but is it easy enough to fix mistakes and come up with a good product?

[Rod]

Hi Richard

I would say it's more a test of patience. You can correct any mistake you make , short of breaking the glass! The bit I found hardest with my second mirror was parabolizing and testing. Once a friend took me through that process I was fine with other mirrors I made. Slow mirrors are a good way to go like Mark suggested. My first was a 6 inch f10. I just left it spherical and it worked really well.

Don't expect to save money making your own. Do it only if it interests you as an end in itself.

Rod

[OzEclipse (Joe Cali)]

A good optician could have polished the Mt Palomar 200 inch in less time than I spent polishing my first 6" f7 mirror. My mentor could see that I was an impatient 15 year old so he made me polish out a severely turned down edge just to teach me patience. It also gave me a lot of confidence in my own abilities. With him riding me hard and giving a LOT of guidance, the mirror turned out as close to perfect as you could expect. I don't have a test figure for it but when it had a good coating and the seeing is perfect, I've had a 6mm eyepiece with a 3X barlow (500x) and the planets were crystal clear. If I'd had a shorter eyepiece combo, I suspect i could have gone higher.

It's had a crummy coating on it that doesn't do justice to the figure for more than 10 years but I want to rectify that soon.

I never did polish a second mirror but I've used the mechanical, manual and engineering skills and the patience and confidence he taught me continuously during the 35 years since both in my work in designing and modifying scientific instruments and at home in making lots of other stuff - both ATM and non-astro.

In 1978, a 6" mirror kit - two blanks - tool and mirror and full set of abrasives cost $22. A 6" telescope in the 1970's cost many hundreds of dollars which was the best part of a months pay at minimum adult wage.

So making a scope was a necessity in those days.

A skillfully made mirror will outperform a mass produced mirror but an unskillfully made mirror won't. Mine has given me enormous enjoyment and I'm about to re-juvenate that crappy coating and get it back to it's best. Be aware that you need to put significant time into making testers and other stuff before you can start polishing.

I recommend you do it, just be prepared to sink a lot of time into it. And remember that the aluminized coating alone will cost more than buying a mass produced mirror off the shelf today.

Joe

[richard3030 (Richard)]

Thanks guys. That makes me feel better about embarking on a mirror-making journey. I'm still quite worried that I won't be able to do a good enough job to make a usable mirror, but I think with some guidance and a lot of patience it should be doable.

I certainly understand that this won't be an exercise that will save me any money, it will purely be for the satisfaction of having done something awesome for myself, and sentimental as a gift.

[Satchmo]

Hi Richard- if you want to make a 6" mirror that is spherical and will perform well - make it an F10. An 8" is more useful and easier to hold. An F7.5 to F8 only requires a slight parabola and the biger footprint of the scope will make it more stable. There is so much information available on the internet now it would make it easier , and there are ATM forums like Cloudy Nights and here where you could post pictures through your tester.

For your first scope I would recommend a configuration like the original Dobsons with a box down the back end that makes it easy to pull the mirror in and out, and just take your time and finish the mirror by looking through a Ronchi grating at a real star. That is called a Null test and when the mirror is good the lines will appear straight ( bending of the lines ) . It is quite sensitive at F6 to F8 for looking at real sky but much less so at F4 to F5.

I have on past occasions looked at home built scopes whose owners swore were really good , but a simple 100 lines per inch grating showed obvious spherical aberration. You can also check your mirror on a star with an eyepiece and look for residual spherical aberration that way , which was the method that John Dobson favored.

There are great resources here if you haven't allready seen.

http://stellafane.org/tm/index.html