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Re: (ATMoB:Discuss) mirror coatings questions
Bob,
Research Service Co. in Revere does AlSiOx (aluminum with silicon monoxide coating for ATMOB members at $3 per inch of aperture. Reflectance is broadband from Violet to deep Red and averages 88%.
Many "enhanced" coatings are peaked to 94% by using other overcoat materials or multi-layers. The reflectance falls off at other wavelengths.
The best reflector coating, after many years, still seems to be Denton FS-999 Overcoated Silver (Cherry Hill, NJ) at 99% broadband visual, but sometimes fails prematurely, especially if exposed to moisture or sulfur-bearing smog. The failure is usually appears as black pock-marks that grow with time.
Celestron used this coating but I do not know if they still do.
There are many 99% dielectric coatings, but they are intended for a specific angle of incidence and a very narrow band such as a laser wavelength. (Also very expensive).
Clear,Dark Skies,
Paul
>
> From: "Smith, Robert W. (Tech Writer)" <Bob_Smith ^a^ bose dot com>
> Date: 2002/06/13 Thu PM 02:34:33 EDT
> To: "'atmob-discuss ^a^ atmob daht org'" <atmob-discuss ^a^ atmob daht org>
> Subject: (ATMoB:Discuss) mirror coatings questions
>
> Hello All,
>
> Does anyone out there know of a local company that does mirror re-coating?
>
> Also, I have seen comments for and against enhanced coatings on primaries
> and secondaries. Swayze states that enhanced coatings are not recommended,
> but others use them. Any ideas why enhanced coatings may not be useful for
> amateur optics?
>
> Thanks,
>
> Bob Smith
> Marlboro, Ma.
>