Possible unwanted behaviour of scale factor?

[Andrew Atkinson]

>
> This paper might be of interest...
>
> <URL:http://optics.sgu.ru/_media/optics/staff/bashkatov/
> bashkatov_spie_03_5068_393.pdf>
>
> (just another Google search :-)
>
> --
> David Gibson

Yep found one, seems to confirm 1.33(3) is probably good for temperature
and wavelength. Suspect impurities do not alter it that much, but will
check with a traditional tape measure

Andrew