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Old 10-10-2011, 06:59 PM
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sopticals (Stephen)
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Any amateur mirror makers still alive in Oz/Nz?

Any amateur mirror makers still alive in Oz/Nz? I dont see any evidence in recent times of posting in the down unders of backyard mirror makers.Anybody out there? If so what are you up to at the present? Mirrors being made? Successes /failures? Biggest/smallest? Newts/Dobs? Future projects planed etc. As one who has returned to telescope making (in this last 18 months, after about a 40 year absence), I would love to hear from you. Currently I am working on a nearly finished 25" f4.7 Dob the mirror of which I am figuring at the moment. Also at the figuring stage on a 22" f5.2 mirror. I must admit Im maving lots of fun. I had almost forgotten how exciting and challenging making a good mirror can be. Thanks for your imput (in advance).
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Old 10-10-2011, 07:51 PM
ColinandRos
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Yes, still at it in Oz.

I finished a 20inch a few months ago.

I do not see anything amaterish about your endeavours.

I have mirrors to be made better before getting any more glass.

Where do you get yours from?

Colin.
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Old 10-10-2011, 10:12 PM
Rod
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Hi Stephen and Colin,

I make my own mirrors too but only in the 4 to 12 inch range (so far).

I have a long term project to complete - 14 inch F4. Originally intended it to be a Dall Kirkham Cassegrain. Currently I am trying to decide whether just to make it into a Fast newtonian. Mirror is polished spherical but needs figuring.

I also recently picked up an 8 inch classical cassegrain mirror set very cheaply. I may make my own secondary for it as the one that came with it may not match. The seller was not sure if they were part of the same set. I recently acquired an 8 inch F2 sphere so testing it should not be a problem.

Good to hear from other mirror makers. I think we are a rare breed!

Regards,

Rod.
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Old 11-10-2011, 07:29 AM
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Rod-Great stuff. My first project was a 7" EQ Newt back around 1962 as a 17 year old,(no Dobsonian options in those days).Even with the f7.5 mirror the scope was a monster with its 1/8" alluminium tube and massive EQ mount (my own design) made of cast iron having 1" bright steel shafts, a 3" pier (boiler pipe) with "hens foot" base also 3" pipe. The thing must have weighed 100kg. However it performed for me, being able to use out to 40-50x per inch of aperture.Compared to the 3" reflector (Japanese origin) bought from a local camera shop, its performance was the difference between night and day. In those days in NZ with the import restictions and such it was almost impossible to buy a reflecting telescope of greater than 3" or 4.25". The only 6" and 8" (biggies in those days) were home made. Now days biggies start at around 14", and again the only affordable way to go (if your budget is limited), is to fabricate ones own from the ground up. I figure that in real money terms that my current 25" Dob project will cost less (thanks to the brilliance of John Dobson and his simple concept), and actually weigh less than my original 7" Newtonian. With all the information available online its as easy to grind a 20"+ scope today as it would have been an 8" 50 years ago.
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Old 11-10-2011, 05:45 PM
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Quote:
Originally Posted by ColinandRos View Post
Yes, still at it in Oz.

I finished a 20inch a few months ago.

I do not see anything amaterish about your endeavours.

I have mirrors to be made better before getting any more glass.

Where do you get yours from?

Colin.
Hi Colin, thanks for the post. I agree with your philosophy, regarding improving the glass you have. When I put my Dob together I will first of all test the primary without coating on moon, planets and stellar objects.I know only around 5% of incoming light will be reflected (about the light one would expect of a 6" reflector), but even with the diminished light one can evaluate to some degree resolution etc. If that test is passed satisfactorily then the next step would be to silver coat, which I can have done for around NZ$50. If everything was ok I would Aluminize. Otherwise a further figuring iteration would be the order of the day.

I have a son connected to the domestic glass/mirror industry so my glass is not too expensive. However the thickess I can get here in NZ seems to be 19mm float so a little limited on how big a mirror one can go. I have tried suppliers in asia for large blanks but invariably (so far) have been quoted US$5000 plus for blanks (borosilicate) of 30" diameter with thicknesses of 30 to 40mm. So well outside my budget. My current Dob (completed) should come in at around NZ$1000-1200. Where do you source your glass in OZ? I hear 1" plate can be got in Sydney.

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Old 11-10-2011, 09:04 PM
cristian abarca
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Mirror makers

Hi guys Ive made a few mirrors/telescopes. My first mirror was an F7 Newtonian. For a first mirror it wasn't too bad it had a small turned down edge but it I used it successfully for a few years. I made a couple of others that never made it into telescopes. I've also tried to make a classical cassegrain that I could use as a fast Newtonian as well, just exchange the secondaries. The primary is an F4.55 and it is a good mirror. The secondary is still a work in progress. I'll get back to it sooner or later. I have a 16 inch plate glass blank which I'll make as practice run and then I'll make a 20 inch. I have a 20 inch Pyrex blank, but my next project is going to be a Lurie Haughton Newtonian. I will reuse the first mirror I made and turn it into an F4 mirror. I should use BK7 glass but as a trial I'll use plate glass for the 2 correctors. About 2 years ago Rod recommended I use plate glass for the correctors instead. I managed to get my hand on two 19 mm 10 inch blanks so I'll follow Rod's recommendation. If it works then I'll do it again with the BK7 glass.

Cristian
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Old 12-10-2011, 06:30 PM
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Hi guys , I've never tried mirror making but plan to soon , I have a 12" scope that I'd like to put a homemade mirror in one day but realise
thats a fair way off .

So for now I've bought a 6 " blank and materials to have a go at it .
As I built a test stand and started building a tester a couple of years back I thought I'd build and finish the scope first so as to maybe move things along a little quicker .


I'll start a thread here sometime on how it goes and your sage advice is most welcome
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Old 12-10-2011, 07:09 PM
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I'll start a thread here sometime on how it goes and your sage advice is most welcome
is it started yet?
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Old 12-10-2011, 07:51 PM
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[is it started yet?]
fair comment!! soon ,, real soon
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Old 13-10-2011, 12:18 PM
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sopticals (Stephen)
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Quote:
Originally Posted by nightstalker View Post
Hi guys , I've never tried mirror making but plan to soon , I have a 12" scope that I'd like to put a homemade mirror in one day but realise
thats a fair way off .

So for now I've bought a 6 " blank and materials to have a go at it .
As I built a test stand and started building a tester a couple of years back I thought I'd build and finish the scope first so as to maybe move things along a little quicker .


I'll start a thread here sometime on how it goes and your sage advice is most welcome
Hi Graham, the 6" size is great to start with. My first mirror was a 5.75" and was a great exercise, but was I admit (in hindsight) a bit rough. However gave not bad views. In those days you started with a rough cut (about a dozen sided sawn) piece of 1" plate. I asked for a diameter of 6.25" hoping that by the time I had ground it into a circle it would have been 6", but lost a full half inch in the translation.

With your 6" blank I would suggest you make it to f10 as at this optical speed a spherical figure would be ok,and assuming your 12" dob is f5 then the focal lengths of both mirrors being the same, the 12" dob structure could double as a test bed for your 6" mirror.
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Old 13-10-2011, 06:00 PM
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Thanks Stephan, I never thought of the 12 " as a test bed .

The 6" scope itself componant wise is pretty close to finished so I'll probably run with it,, its a single pole assembly at the moment
and will be adjustable out to around f 7.5 .. longer than that and I have to buy another bit of tube
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Old 13-10-2011, 06:08 PM
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I like this thread.

I think it would be a great idea to have a mirror making thread section on IIS which would allow people to start threads on their mirror making progress and swap ideas rather than a thread being buried in the ATM section which tends to be mainly about builds and rebuilds using commercial mirrors.. What do you guys think ? . I would be happy to be moderator on it in the sense that I would try to keep things 'focused' and keep my eyes on the section and lend advice where I can.

Mirror making is something that is almost approaching a lost art in comparison to 40 years ago where if you wanted a `huge' 6" reflector you would probably have to grind one yourself as a 6" mirror would have been a weeks wages. I don't think any amount of the advanced work I do these days can replace the romance of the art I felt as a 14 year old , walking around an old washing machine with a 6" blank on top - the smell and sound of fresh Carborundum cutting glass and the smell of resin on a lap and the excitement of seeing my frosty glass take on a shine which I could reflect light from.

I read somewhere that it was the introduction of the C5 and C8 that spelled the dell knell for the ubiquitous 6" or 8" reflector on a pipe equatorial that we aspired to . The Asian Dobs revived the Newtonian in the 90's but I don't think mirror making as a hobby ever recovered.
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Old 13-10-2011, 07:53 PM
Rod
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Quote:
Originally Posted by Satchmo View Post
I like this thread.

I think it would be a great idea to have a mirror making thread section on IIS which would allow people to start threads on their mirror making progress and swap ideas rather than a thread being buried in the ATM section which tends to be mainly about builds and rebuilds using commercial mirrors.. What do you guys think ? .
Hi Mark,

I think that would be great! Personally I think it would help keep me motivated if I could share a project via a thread like you suggest. Having advice from people like youself would be a fantastic opportunity.

Rod.
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Old 14-10-2011, 01:56 PM
cfranks (Charles)
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Just a comment for those starting a 6" scope. An 8" is almost exactly the same cost and effort/time to make but you get 2x the amount of light with it.
My first telescope, a 15" f5.6 Dob was made in '86 and is still in use at ASSA's Stockport facility. Subsequently, I made dozens of smaller ones for other people but not for many years now. I've got that medical problem of Chronic Repetetive Birthdays! I've still got some 10" Plate blanks somewhere if anyone is interested.

Charles
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Old 14-10-2011, 06:34 PM
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Hi Mark,(and all), a mirror makers thread would be a great idea. But are there enough of us (glass pushers) "down under" to keep such a thread alive? In these "instant this and instant that" days with commercial options for everything, its hard going for the "do it yourselfer" to get motivated, unless (as in my own case), one is restricted by budget limitations which make it necessary to make ones own as the commercial equivalent is out of the question. Plus there is immense satisfaction in successfully grinding, polishing and figuring your own mirror, which when built into a scope, can put you way out there in the midst of that great celestial wonderland of planets, DSOs, and "fly over" views of the moon.
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Old 14-10-2011, 07:19 PM
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I think a thread souly for mirror making would build to be a good resource in time for those wanting to try there hand at it.
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Old 14-10-2011, 07:58 PM
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fair comment!! soon ,, real soon
has it started yet? (I have a 6" pyrex blank here somewhere)
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Old 15-10-2011, 10:43 AM
bobson (Bob)
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Quote:
I think it would be a great idea to have a mirror making thread section on IIS which would allow people to start threads on their mirror making progress and swap ideas rather than a thread being buried in the ATM section which tends to be mainly about builds and rebuilds using commercial mirrors.. What do you guys think ?
Great idea Mark!

cheers

bob
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Old 15-10-2011, 12:05 PM
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Hi Mark,(and all), a mirror makers thread would be a great idea. But are there enough of us (glass pushers) "down under" to keep such a thread alive?
Hi Bob

I had in mind not a thread as such but a separate section like ATM but perhaps called Mirror Making

So far there seems to be good support for the idea. I'll point Mike to it if he hasn't already seen it .
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Old 18-10-2011, 11:29 PM
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Hi all,
I'm at the figuring stage of my first mirror blank, an 178mm F4.43, after working on and off for about a year. This is my first attempt and I'm happy with the results so far. It has been a very good learning curve which in experience alone will be great in making my next mirror.
It would be nice to a mirror making section in ATM.
Cheers.
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