Re: [ATM] Multicoatings

["Tony Owens" <towens@shibumi-consulting.net>]

Chris,
There is a whole branch of optical engineering to do with coatings.  Single
layer coatings like magnesium fluoride are simple enough, and can give a
decent result on most glasses if thickness is tightly controlled.  AR
coatings don't increase light transmission of a glass directly.  But by
stopping a part of the light which enters or leaves from being reflected at
each of the glass/air interfaces it is free to go through the glass instead
- so light throughput thru the lens gets better.  Don't know if I'm
explaining that very well?
Broadband anti-reflective coatings (BBARC's) are usually used to decrease
unwanted reflections off glass/air or air/glass surfaces.  The composition
of the coating is many very thin layers of exotic materials deposited in a
particular sequence with tight thickness control.  There is nothing
arbitrary about them - they need to be customized to the refractive index of
the glass type and the mean angle of the light rays as they enter/leave the
glass surface.
Manufacturers of quality kit will have specific BBAR coat formulas that they
use, for each individual glass type used in their designs.  If you need an
SCT corrector recoated (why do you think you need this?) I'd talk to the
manufacturer first.

Tony

-----Original Message-----
From: Chris Dalla Piazza [mailto:dalchri@hotmail.com] 
Sent: Wednesday, August 08, 2007 2:15 AM
To: atm@atmlist.net
Subject: Re: [ATM] Multicoatings

Here's another way to ask the question.  What do Meade, Celestron, Televue, 
Takahashi, and Astro-Physics use to coat the optics on their refractors and 
the corrector plates of their catadioptrics?  If I needed to get a corrector

plate from my SCT recoated, where would I do this and what would I ask for?

This is for the corrector of my recently completed Lurie-Houghton Newtonian.

Thanks again for suggestions!


>From: "Chris Dalla Piazza" <dalchri@hotmail.com>
>To: atm@atmlist.net
>Subject: [ATM] Multicoatings
>Date: Tue, 07 Aug 2007 11:25:05 -0400
>
>I have a few questions about multicoatings I was wondering if someone could
>help me with...
>
>Do multicoatings increase transmission or do they only eliminate 
>reflection.
>
>I understand there are a few different types of multicoatings.  Is there a
>standard or most widely used coating?
>
>My priority is that there be no weird colors when imaging rather than 
>really
>high transmission.  What coating would you recommend?
>
>Finally, who would you recommend?
>
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