Hello,

Turns out it is pretty easy to tell. Take the filter outside on a sunny
day. If you have the photographic type film (3.8 ND), you will be able to
see through it when you hold it up in front of you. With the visual type
film (5 ND), you will not be able to see anything. You can then hold it up
between you and the Sun. With 3.8 ND, the Sun will be too bright to look at
comfortably.

Best regards,
Mike Swanson
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
http://www.NexStarSite.com

-----Original Message-----
From: Baader-Planetarium@yahoogroups.com
[mailto:Baader-Planetarium@yahoogroups.com] On Behalf Of patrickduis
Sent: Thursday, February 12, 2009 8:14 AM
To: Baader-Planetarium@yahoogroups.com
Subject: [Baader-Planetarium] Baader solar filter

Hi, a few months ago I bought a fairly cheap (around 40 euro's) 2nd
hand (self built) solar filter for my 8" scope. When I look through
the filter towards the sun I can see it very nicely. Up till now I
didn't dare to look dat the sun with this filter because I recently
found out there are 2 grades. 3.5 and 5 ND. Is there any way to tell
which grade it is?



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