Polarising filters for visual

[25585 1,318]

How good are revolvable polarising filters for reducing light pollution and moonlight from most affected areas of sky?

Also for seeing bright objects and reducing brightness that covers near neighbouring objects?

[Ruud 3,254]

These filters dim all wavelengths.

They're only good for the face of the Moon, if it's too bright for you.

Edited January 30, 2018 by Ruud

[LukeSkywatcher 15,482]

By "revolvable" i assume you mean variable (2 part) filters. Variable polarizing filters are a bit more expensive. A single polarizing will do. You dont even need that to be honest. A single polarizing filter will do.............or just a standard Moon filter.

These will only cut down the brightness. They wont have much effect on cutting down light pollution. 

To help reduce LP, you need a light pollution filter (LPF). They help. It depends how much you can spend. 

Its a personal choice if you use a Moon filter or not. LP filters........work, depending how bad the LP is.

Edited February 3, 2018 by LukeSkywatcher

[SpaceWalker 51]

I observe mostly in a Red Zone and, frankly, I don't know any EFFECTIVE LP filter. Any polarizer is useless for LP reduction. Sometimes UHC can help but not much. As they say, the best is a "gasoline filter", when you load full tank and drive to a dark sky area . Or wait for a moonless night.

Variable polarizer is good for closely located objects different in brightness like Sirius A and B etc.  You can cut the price by getting 2 inexpensive single polarizers e.g. from eBay or so. Attach one to a diagonal or 1.25/2 adapter (in reflector) and the other one to eyepiece, or better, to an extension tube and you can change eyepieces on the go.