Filters

[Speicus]

What do sextant filters filter?

I think this is an important question when looking at the sun. If only visible light is filtered, my pupil widens and lets all ultraviolet through, like with low quality sunglasses. This will harm my eye.

Mine is a second-hand Freiberger sextant - I cannot find any specifications. Does anybody have any information?

Regards

[Rdutton]

That's a very good question since most sights we take are of the Sun. There's no information that I could find about my Astra III-B. That said, it appears that regular glass will filter out UV pretty well. But how much is that?

This might be helpful- http://www.physlink.com/education/askexperts/ae603.cfm


Roland

[Rumata]

Greetings,

I used Julbo for mountain climbing ( snow, ice, a tons of reflection). Also there is anew type ( admittedly for climbers) Belaggle ( or something) which permits you to look straight and up without raising your head ( they use prizm configuration). I always thought that glass vs plastic should be glass. The first indication you temporary burn your eyes is a feeling like someone throw sand in your eyes. By the way, it is the first affect of ionizing radiation. Before your body catches it-your eyes indicate it by strong itching. Used Astra III with no problems. So far ;> ;>

[EdCa]

I was reading about an UV lamp that kills bacteria in a domestic water supply. The directions said to only view the UV light through a normal pane of glass. So, the glass filters on our sextants will block the UV rays and protect our eyes.

Ed

[Rumata]

I was reading about an UV lamp that kills bacteria in a domestic water supply.  The directions said to only view the UV light through a normal pane of glass.  So, the glass filters on our sextants will block the UV rays and protect our eyes.

Ed

I think the main consideration should be given to the intensity of UV light.  I have a little device with UV light to filter outdoor water. Tried it once and still alive.  It uses 2 AA bateries. I think its power not exactly the same which is coming from the Sun. But, yes, the glass supposed to be a good protection.

[Speicus]

I learned from a colleague that not all glass is the same. He worked a summer in greenhouses cutting tomatoes and came back with a deep tan, despite always being "inside" under the glass roof of the greenhouse.
Apparently, greenhouse glass is not "normal" glass; can we be certain that sextant filter glass is?

After wading through many pictures of Freiberger horses, I found the website of the sextant manufacturer - I think I'll send them an e-mail.

[P.Rutherford]

If  you're familiar with this movie scene below you know it has nothing to do with sextant work.  Let's just say it did.

"It 'twas.....sun...sights!"