[APML] Exposure time with filter

["=?utf-8?Q?nmontec@libero.it?=" <nmontec@libero.it>]

Dear All,

I send this question again as you probably didn't receive my first one.
I wanted to buy a dark red filter in order to prevent light pollution 
but filters like wratten #92 has a factor 8 as absorbtion. Is this true 
that I need to expose for a time 8 times longer than before? So an 10 
minutes exposure becomes an 80 minutes exposure? I need to understand 
this because if this is true I cannot do that way as I don't have 
autoguide....:-/

thanks
Nicola



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