Lens Coatings

[Jared]

Hi. I've just signed up to IceInSpace.

I've been using some cheap 10x50 binoculars on-and-off for about a year and have just put a pair of Celestron 15x70s on lay-by (still pretty cheap I know, but not as cheap). Celestron says they're "multi-coated". I've read somewhere that sometimes the lenses are coated but not the prisms.

Firstly, I was just wondering which applies to my Skymasters, and secondly, what exactly are lens coatings? ... what material are they made from, what is the application process, what effect does it have on the performance of the binoculars, exactly how does it alter the behaviour of light etc.

I am really interested in this aspect of astronomy at the moment and am ready to soak up any knowledge that anyone might have.

Thanks a lot.

[RB]

Welcome Jared to IIS.

You've come to the right place and I'm sure you're questions will be answered soon.

Hope you enjoy your visits.

RB

[janoskiss]

:welcome: J.

Coatings on lenses are designed to minimise reflection and maximise transmission of light.

In binos you want fully multi-coated (FMC) optics, if you can at all afford it. You can get good FMC binos from www.aoe.com.au starting at around $100.

coated = at least one air-glass surface has at least a single layer of coating
fully coated = all air-glass surfaces have at least a single layer of coating
multi-coated (MC) = at least one air-glass surface has at least multiple layers of coating
FMC = ... well you get the idea.

Multi-coatings work on multiple colours, single layer coatings are tuned to just one colour. The best multi-coatings work at right across the visible spectrum.

In practice FMC will give you higher contrast, less light scatter and less reflections and glare off bright objects.

[Jared]

Thanks for replying!

I wish I'd gotten that advice before I commited to buying the Skymasters ... I hope they aren't complete duds. I was working with the idea that you get what you pay for, but maybe a $100 pair with FMC lenses would be better than a $240 pair that are just multi-coated.

I think I'll take xelasnave's advice that I found in the "how much is your equipment worth" thread:


I'm sure I'll still have a lot of fun.

[janoskiss]

I guess it's size and maybe to some extent the brand name that you are paying for there. You almost certainly will see more stars with the bigger binos, but the FMC optics will, in general, produce a brighter more contrasty image. It's kind of like a good quality mini-hifi vs the biggest baddest-looking kmart special boombox. The latter will be louder but the former will produce a more pleasing sound.

But MC can mean a lot of things from one glass surface multi-coated to all but one. I'm guessing that Celestron MC binos should be pretty good. Even FC cheapies from Celestron do quite well considering they are only FC. And their FMC Ultima DX's are very nice, with excellent price/performance ratio.

[Jared]

Thanks again janoskiss.

I suppose I'll just have to wait until I get them and see how they go ... I'm not sure I'll be able to tell the difference anyway.

Regardless, I'll let you know what I think once I try them out ...