Mylar vacuum mirror

[robz (Robert)]

Thanks Bojan, and I respect your comments.

I have emailed Peter Waddell and have asked a few critical, straight to the point questions regarding the curve and whether it's suitable for a telescope mirror.

Also questioned was the surface quality/accuracy of the Mylar, and whether the mirror housing construction can be simplified without massive industrial machining costs.

I stated that if this was at all possible, a large mirror was in consideration, not a small one, otherwise purchasing the real thing would be a better alternative.

I hope he replies..........with good news, not bad.
I'm not expecting to hear anything positive some how.Either way, I'll report my findings to the forum just the same

Rob.

[robz (Robert)]

O.K,...over the weekend, Peter Waddell has replied....3 times, has asked for my address and will send documents, measurements and data.

In short, without directly quoting him :
1. The curve shown previously is for special 3D/STEREOSCOPIC IMAGING purposes and would not be relevant for telescope usage.
The same problems that exist with a hyper fast glass mirror, also apply to the Mylar mirror in regards to image distortion etc.
2. He has stated that with the project's success and recent developments and applications, ''you will be amazed at the results that can be achieved''
3.In regards to the thickness of the mylar..............he mentions using 100 micron(10 mil ) !!! thick film......................not 4 or 5 mil which is commonly available from your local agricultural/horticulture shop.
Thus my suspicion on why ''thicker Mylar'' has been the only option, and him mentioning in an article that the choice/type of Mylar is important.We may also be dealing with a particular ''grade'' of Mylar here............who knows?

4. for a telescope, at a reasonable focal ratio, he stated that the results would be ''fantastic!''

So, ..............he has stated that he will gradually assist with information and advised that I ''standby'' for further news.

I don't know what y'all think about this so far?................it's easy to slag off this method when we're all used to ground and polished glass for our optics.
To me, I sense that something of great significance has been missed(ATM wise) in this invention all these years ago
I mean, who would have even considered that 100 micron thick Mylar is even remotely acceptable to stretch in to an accurate curve????............... .surely the thinner the better I would have thought?

More importantly.........and this is significant whether you like it or not, he NEVER said........Rob, forget it...............this is not a workable system for astronomical purposes I'm afraid................so,.......... ...................he probably knows that it DOES work.
The question is,as he did not answer my relevant and specific questions on the details of the mirror mounting system, is whether it can be done on a largish scale without spending thousands on advanced machining technology etc.????
I think that the details coming in the mail and forthcoming information/conversations may answer this?

[bojan]

Thick mylar means, he had a problem with sagging due to the weight of the mylar itself... plus rippling due to air turbulence near mirror.. plus who know what.

Why not go straight for a thin glass plate?

I advise you to forget about it...
If this approach is/was of any worth (with currently available materials), it would have been in use already, IMHO.

[robz (Robert)]

Bojan, fantastic attitude mate!.............................. I wish that all developers and researchers had that method of thinking............we'd still be rubbing two sticks together to make fire in 2010...........at least that's a ''proven method'' that works and fires are lit that way everywhere

[bojan]

Entirely up to you mate..
Your time, your money.
I've been there, done that ...

[robz (Robert)]

I'm not spending a cent until I infuse as much information on this as possible. Even then I may not proceed.............it all depends on the logistics if there are any worth considerng.
S***.............let's give Wadell half a chance for heaven's sake.............this is ridiculous!
Unlike a lot of people, ''been there done that'' doesn't cut it with me.
I'm willing to investigate the failures with intense interest.......not just give up and spread the bad news.

There's a new thread on another forum on a ''giant binocular telescope'' using ADAPTIVE OPTICS.

Now this is right up our slagging territory fellow ATM's...............a thin glass disk that has heaps of magnets glued to the underneath. These magnets are actuated by an electrical field to pull the mirror in to shape.

Sounds crazy?...................yeah, the developers were told that right from the start from what I recall, yet here they have the working product ready to go

[Miaplacidus (Brian)]

(Getting a tad *****y, here, children...)

If it could work, then this would seem like a nice project to launch into space, where some of the objections alluded to in this thread might be overcome, and some truly gargantuan mirror might be assembled.

Then GSO can get to work on the clone version....

[Peter Ward]

I knew I had read something on this in Sky & Tel. With a little digging I found this

http://home.freeuk.com/m.gavin/flux.htm

The author quaintly puts the airy disk size or "circle of confusion" at around 5mm....this is several orders of magnitude worse than a diffraction limited
glass mirror

[bojan]

Originally Posted by Peter Ward

I knew I had read something on this in Sky & Tel. With a little digging I found this

http://home.freeuk.com/m.gavin/flux.htm

The author quaintly puts the airy disk size or "circle of confusion" at around 5mm....this is several orders of magnitude worse than a diffraction limited
glass mirror

Also, the owner of the telescope with mylar mirror must be VERY quiet when using it - electrostatic microphones are designed around a mylar membrane, which moves as acoustic waves are hitting a membrane surface. Electrical signal is picked up as variation of capacitance between membrane and back plate.
Another example is something from James Bond movies, but also from real world: laser microphone.. Laser beam reflected from glass window is modulated by the sounds produced inside the room.
Nobody wants telescope mirror shape to be sensitive to sounds, and this is exactly what is happening with thin membranes....

[robz (Robert)]

Yes, I have seen this article, more than once.The article is ancient, stupidly implemented and does not relate to a telescope mirror in the trues sense, yet it's posted here for me to be ''informed'' that the Mylar mirror idea is a waste of time!

What the hell does one expect when they ''crudely'' stretch film on bike rims without any consideration towards evenness or optical flatness as a first and most important pre-requisite and then expect perfect optical performance while the frame bends under vacuum forces.............c'mon everyone..............get a grip on this.

I've said it before.............LOOK AT THE PATENT..............is it a couple of bike rims with metalised glad wrap?????

It's a complex system designed to control every square mm of that Mylar and it's subsequent tensioning and contact with the purposely designed wide rim when a vacuum is applied.
Is everyone ignoring the details or just not bothering?

If we're going to talk about audio and microphones, I'm an expert on that with direct experience as a recording engineer .
Microphones do have ''thin'' membranes............the Wadell mirror is 100microns.............one hundred + times thicker than an electret microphone.............le t's leave that one for ''James''.

If we consider vibrations in a telescope, I have seen some of the very best wobble like jelly in a slight breeze or nearby foot steps at moderate to high power(Perth Observatory)

I'm not defending the Wadell mirror or his methods and am no way affiliated with him apart from email contact and some documentation that I am waiting upon.
I would have thought that this thread would be of benefit to my fellow ATM's, even if it was just considered as a possibility until further documentation came to light.
The result has been the opposite with critics who insist that it's impossible when they know the product is in existance and in use.

Irrespective if the application is relevant for telescopes or not, my expectation was to at least generate some interest and ''positive'' input towards the subject and not just ''been there done that''......... when you know quite well that you did not even get close to what's required as a start to possible success.

With all due respect to those who read the thread with some interest but did not contribute post wise, I personally will stop posting on this subject from here on.

Happy observing

[bojan]

Rob,
I am sorry if I offended you in any way.

I was just trying to point to some problems I encountered when playing with this idea back in late '60-ties.

This was not a criticism for the sake of criticism, in my opinion it was a contribution to a discussion.. . You cant' have only positive response on the subject when there are people out there with negative experience.

Anyway, if you succeed, please let us know. I will be happy to try all this again, knowing someone has really done it.

[robz (Robert)]

No offense taken Bojan or anyone

If there is anything worthy to report on in the future, I will do so.

Cheers,
Rob.

[robz (Robert)]

O.K,..................FINALLY!..... ..............got an email back from Peter Waddell..............quite lengthy as my wife has just informed me.

When I get home from work, I'll check it out and report on what it entails.

In the mean time I got a couple of responses from another astronomy forum yesterday.
Interestingly,one person had tried two 24inch ply wood rings and mylar over some sort of steel container and initial tests were positive, but the project was never carried on with due to family moving and commitments.

Anyhow, standby all

[robz (Robert)]

The email from Peter Waddell has advised that documentaion on the mirror's performance at conventions and seminars and proof that superb results have been obtained in fine resolution imaging are on their way to me.

Peter has asked me to email him immediately after I receive the documents and he will begin to provide instructions on how to build the mirror and where to buy the materials.

This may be a first for ATM as this information has been kept under close wraps for many years now.
On top of that, the critical methodology required in it's construction will be of great value as this is what makes or breaks a successful working product.


Rob.

[robz (Robert)]

I have received the documentation as promised.

Some of it(and there is a hell of a lot) I have already come accross on the net, most I have not seen. Generally it relates to 3D imaging applications.

My email to Peter tonight will confirm that I have received and read the documentation.

I will pose the question if this system will work for telescope applications and ask for his assistance in the manufacturing of such a device without resorting to expensive materials and machining(if at all possible).

[robz (Robert)]

Got a reply back from Peter Waddell.

As suspected, he has mentioned the need to have a large and accurate ''ring'' made for stretching the mylar over it's curve. He suggests that this may be built in sections to form an entire circle

As well, he is talking about finding out about 150 micron thick mylar sheet (as opposed to 100 micron) for me as a start to the project.

I already know that there is at least $200-300 minimum length costs here alone

Interestingly, he stated that a ''solid'' version of the membrane mirror was even developed, but it's use for 3D imaging was overshadowed by the release of commercial 3D flat T.V. screens and the project was discarded as a result.

I don't really know what to make of all this. If I knew for certain that it would work I'd go for it...............but I can see a gamble here at great cost possibly

[Merlin66 (Ken)]

Look upon it as an investment or the cost of entry to this exciting technology....
Once you've cracked it the cost won't mean anything compared with the partical experience and knowledge you will have gained!!
( I "invested" about $13K in a venture to design and manufacture a cost effective intermediate spectroscope...don't know if I'll ever recoup my costs, but the amateur community will/ are getting the longer term benefits!)

Ken

[jossupp]

I play whit millar Mirror and glass plate also

BUT

it is not for Imaging purpose or astronomical purpose

only for collecting lot of light from dark moon in the moon impack group

we just need lot of light to detect the impack of meteor on the dark side or part of the moon
because that we do not need perfect image jus collect lot of light

ALSO

>I work in spectroscopy
AND there also just need lot of light
we are limit to about mag 12 for the moment but whit a 30 inch chaneway Mirror we have maybe all the light we need and go to mag 14

also probalby working in off axix we do not care about astigmatisme

just a big collector of light

the work of all the mylar grop a re good but it look like they do not know the vacuum produce a chaneway curve not a parabola

maybe like the pheric Mirror whit pulling give a parabola

maybe a chaneway just by pushing give a better parabola
that is my next reshearch

jack 47'n 71'W

[jossupp]

the catenaway and parabola have this math formula

generates a parabola
y=a x2 +bx+c
catenaway
y = a + bx + cx^2. parabole
y = a/2 * (e^(x/a) + e^(-x/a) chainette catenaway



jack 47'n 71'W

[jossupp]

if you plot the 2 formula that give you this
http://www.knewance.com/comparisons/...-catenary.html

or this
http://www.clausentech.com/lchs/dcla...h_Excel_v2.pdf

but if you put the start of the plotting at the same place you can see the catenary can be push ((( like a flex can be pull http://media.skyandtelescope.com/doc...MirrorFlex.pdf )))

the catenary probalby can be push also

my test just beging

jack 47'N 71'W