Mylar vacuum mirror

[Shiraz (Ray)]

this might be worth a read (note Roger Angel is one contributor!).

Their method yields a spherical shape. also note the authors' contention that this type of technology is not suited to terrestrial mirrors (due to gravity and sound).

http://fp.optics.arizona.edu/loft/Pu...PIE%204451.pdf

[Wavytone]

Robert, do not waste your time and money. You really need to gain a clear understanding of the tolerances for the surface to be used for forming an image, vs the uncontrollable surface errors that will arise in what you propose.

FWIW I was able to solve the differential equations to calculate the surface profiles analytically and showed that what you will get is not satisfactory - not even close to parabolic, optically.

I will also add this idea has certainly been tried even earlier. One effort I am aware of is that of Ed Simmonds circa 1986, then president of CAS, and at the time I recall Ed saying he was aware of earlier attempts.

Initially Ed had the AAO workshop knock up some massive adjustable aluminium rings to flex 1mm glass disks cut from rejected 18" Schmidt plates into shape, the clear aperture was about 350mm. Ed also tried mylar, with a vacuum behind. The point of using the Schmidt plates was that they were accurately flat and plane parallel to better than a wavelength (though this is still well short of 1/4 wave).

I had the opportunity to test both the glass and the mylar versions. Both were dismal failures, they were only suitable for making solar barbecues - "light buckets" is an understatement.

The 1mm glass sheets typically lasted a few days before shattering as a result of the strain applied - fairly hazardous.

I'll also add that the size of the rings and the vacuum chamber, plus the equipment needed to make it all work is prohibitive, to the point you will rapidly realise it is a LOT simpler to go buy a thin glass mirror.

[jossupp]

((((Robert, do not waste your time and money. You really need to gain a clear understanding of the tolerances for the surface to be used for forming an image, vs the uncontrollable surface errors that will arise in what you propose.))))

yes ok for astro picture but for spectro no need of perfect picture just collec lot of light maybe better goald


((((FWIW I was able to solve the differential equations to calculate the surface profiles analytically and showed that what you will get is not satisfactory - not even close to parabolic, optically. ))))

the catenary is not parabola the formula is simple like the pheric just push ontil pull maybe




(((The 1mm glass sheets typically lasted a few days before shattering as a result of the strain applied - fairly hazardous.)))

I plan to used 1\4 plated glass or simply Mirror in the back do not care bout double reflexion for spectro easy to remove

(((I'll also add that the size of the rings and the vacuum chamber, plus the equipment needed to make it all work is prohibitive, to the point you will rapidly realise it is a LOT simpler to go buy a thin glass mirror. )))

at 30 inch just a byke rimm and little vacuum very sheap setup

for moon impack perfect

realy not for astro picture special purpose only


jack 47'N 71'W