Quote:
Originally Posted by BlackWidow
If I look at the filter it has a mirror finish to it until you hold it up to the light. Then you can see the green colour like looking through an old green bottle..
|
This is what it is supposed to do. The filter only allows a very narrow passband of light wavelength through corresponding to OIII emissions. This light wavelength happens to appear green. You will only notice the green on bright stars.
All other wavelengths are reflected which can reduce their effectiveness in light polluted areas. Light entering the top of the eyepiece gets reflected straight back at your eye from the
mirrored surface. It helps to throw a cloth over your head to keep ambient light out in such situations.