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Originally Posted by Davekyn
Oh yea…About Venus…what you say about glare is true…I tired one of my polarizer’s but it did not make that much difference…I take it somehow the two should be used together…one of them screws in, but then I am unsure how to attach the other filter? Any suggestions?
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One polarising filter will screw into the other. You need to be able to turn one relative to the other so screw one into your eyepiece (it's the 1.25" filters you have?). Don't do it up tight (in fact never screw a filter up tight - they just might be difficult to get off again. You just have to get the light to pass through the filter so a bit loose in the threads for visual observing is fine.) Now screw in the other filter a turn or two. now you should be able to turn the bottom filter relative to the top one.
In fact before you start, hold one in one hand and one in the other and look through them both at the moon. Now turn one of them around in a circle. See what happens. Now you know what to do. I usually have them both screwed on, then with the scope pointing at the Moon or Venus, hold the eyepiece just above the focusser so you can see the unfocussed spot, then adjust the lower filter until I have darkened the view sufficiently, then put the eyepiece in, focus up and observe.
Unlike a single filter, polarising filters are designed to work as a pair - it's called "crossed polars".
(Before you all jump on me, yes our polarising sunglasses are a single polar, but they work on incoming polarised light - eg. reflections off water or car bonnet. Ain't no polarised visible light coming from extra-terrestrial stuff, is there?)