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Old 04-05-2012, 10:49 AM
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madbadgalaxyman (Robert)
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Join Date: Mar 2011
Location: Brisbane
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Quote:
Originally Posted by Suzy View Post
Hi Robert,

The Naglers have got a "coffee tone" colour to them as opposed to XW's for instance that are neutral.
Some people like the colour tone of the Naglers, while some find it annoying as being a false colour tone on stars. I wouldn't know, I don't own a Nagler, but I've read plenty on the "coffee tone" aspect of it.
I admit, Suzy, that I have never paid much attention to the colour tone of eyepieces.

I have a nagging feeling that certain specific so-called "fully coated" eyepieces actually do have an uncoated air-glass surface that is hiding somewhere inside the eyepiece. A single uncoated glass surface usually reflects 3-4 percent of the light that hits it, instead of transmitting that light;
which, in itself, is probably too small a brightness difference for the eye to notice.
BUT - certain glasses of high refractive index can reflect 6-8 percent of the light hitting an uncoated air-glass surface.

I do think that 6-8 percent could be a visually noticeable loss of the light that ought to be reaching the eye, if one takes into account the fact that the unwanted reflected light is going somewhere into the field, instead of into the image of the object.....thereby leading to a loss of contrast between the light from the object and the light coming from the field (the light in the field has a measurable value)

For a couple of years, I was totally obsessive about visually observing vanishingly faint emission nebulae......and I did find that the various small & not-so-small losses of light taking place in the optical train actually did make a difference to the quality of the views of these very challenging objects that are at or near the fringes of visibility.

cheers, robert
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