I've took my 8" f5 skywatcher apart the other day to clean the mirrors, at the same time decided to cut the draw tube out of the way of the light path and installed some light baffles in the tube.
if there were any equations of some sort to determine the size and placing of the baffles, I didn't use them, so I'm not sure how effective it'll be.
I just made sure it didn't "look like" it was intruding into the light path.
below are some phone cam pics of the baffle.. sorry my dslr is out of action for normal photography.
as you can see inside of the tube (looking from the primary mirror side), it gets darker as more and more of the baffle rings are installed. I actually had to wear a torch on my head halfway through glueing the rings..
I've read some conflicting arguments with baffles inside the newtonian tube..so it'll be interesting to see how it turns out.
and of course the clouds moved in as soon as I finished..
Home made rings
http://members.iinet.net.au/~dahn/im...de_baffles.jpg
2 baffle rings
http://members.iinet.net.au/~dahn/im..._installed.jpg
3 baffle rings
http://members.iinet.net.au/~dahn/im..._installed.jpg
8 baffle rings
http://members.iinet.net.au/~dahn/im..._installed.jpg
Front view
http://members.iinet.net.au/~dahn/im...front_view.jpg