Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: EBBCO/filters
    From: Mike L
    Date: 2007 Nov 21, 03:47 -0800

    Hi peter,
    I tried searching and couldn't find the posts.
    My concern with using two polarising filters is that the UV may behave
    differently and not be polarised, so although the optical light is
    diminished, the UV comes through just as before!
    One solution I'm considering is using solar filters for astronomy and
    I quote (http://www.greenwich-observatory.co.uk/acatalog/
    Solar_Filte.html): "BAADER AstroSolar film has become the natural
    first choice for white-light solar observation. It's optical qualities
    are excellent, enabling you to see high-resolution images with a
    natural colour."
    Only problem is that it doesn't say how much the light is attenuated
    and although it ought to be suitable, I've no way of checking out
    before hand.
    The other alternative I'm considering is buying some sheets of optical
    filters - unfortunately with no guarantee on UV transmission so only
    for lunar work (is there any significant UV in moonlight?).
    On Nov 21, 8:10 am, "Peter Fogg"  wrote:
    > Greg R
    > Check out the List archives for discussion on using polarising filters. If
    > you use two in series they can be rotated for increasing combined density,
    > right up to total.
    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site