Air Glow

Here's a newbie question but I'm curious...

What causes air glow and why would it be more pronounced in one eyepiece versus another. I've had several nights where my Celestron plossls display a significant amount of glow around Jupiter. By contrast, if I use my Celestron SMA, there is hardly any air glow. Does the eyepiece design have as much to do with this effect as atmospheric conditions? Thanks

Ken

Hi Ken,
First, are the EPs clean or do they have eyelash oils and such on the lens?
Some EPs do cause more scatter, but magnification would also effect this. More magnification will usually give blacker sky.
So are the EPs of the same focal length?

What you're talking about is commonly called "scatter".

As Floyd mentioned, dirt on the lenses can make this more of a problem.

Otherwise, some eyepieces are better than others at reducing scatter.

Better coatings, smoother polishing, and fewer air to glass surfaces will reduce scatter.

The eyepieces I use for observing planets are TMB Supermonocentrics (least light scatter), BO/TMB Planetaries (most eye relief), and Clave (an excellent but rare top quality plossl).

I think what you are describing is technically not "air glow."
Usually that term describes glow in the upper atmosphere
caused by ionized atoms (usually oxygen).

What you are seeing is light scattering, and there are many
many things that can cause it. From Jupiter downwards:
mist in the air, dew/dirt on optics, poor optical coatings,
focussed reflection in the optics, scratches/roughness
in optics, junk on cornea, scattering inside eye.

The eyepiece is usually half or more of the optical
surfaces, so alot will depend in the eyepiece -- design,
quality of lenses, coatings, etc. The cornea reflects light,
and some eyepiece designs will focus this reflection
back into the eye making for glow, halos, ghost images,
etc. Some eyepieces, for whatever reason, are much more
susceptible to dewing. Maybe the surface chemistry of
the lens is different, or surface is more rough,
or eyecup reduces air circulation, etc.