NavList:

Francis,

As I understand it polarizer pairs block a percentage of light dependant on the relative rotational angle between them from 0° to 90°. Neutral density filters are stacked to block the desired percentage of light. The Sun should appear comfortably dim when using either type of filtering (common sense?). Technical data should be provided with the product used.

Greg Rudzinski

From: Francis Upchurch
Date: 2016 May 6, 18:34 +0100

May I confirm that polarizing filters offer the same UV light/retina protection as standard filters?

Francis

 

From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
Sent: 06 May 2016 18:09
To: francisupchurch---.com
Subject: [NavList] Re: Horizon Shade Polariser

 

Michael,

If two polarizers are screwed together with one polarizer filter flipped in the frame then you have a variable Sun shade. This is very useful at the index mirror when the sky is overcast, hazy, or partly cloudy. I filter this way when doing DSLR camera CN. I like older Vivitar linear polarizers best for this purpose. C&P uses polarizers stock on their current line of sextants.

Greg Rudzinski