This is a great filter.
It will be darker, but for all the good reasons (supressing unwanted bits of light)
You will definately be able to go longer before reaching the skyglow limit.
Have a look at this thread:
http://www.iceinspace.com.au/forum/s...ad.php?t=28782
and this one:
http://www.iceinspace.com.au/forum/s...ad.php?t=33687
The best feature of this filter is that the colour balance is great compared with others. Apparently there is a newer Orion Skyglow filter (compared with the one I had in the comparisons above), but I don't know how that one performs.
This filter in my opinion is well worth every cent. One of the best value for money astro purchases I have made.
Turbo