Paracorr

I understand that the Paracorr add 15% to the mag power of an EP. Is this due to a Barlow type effect or just what?
Also, does it really make that much difference in the view with a 31mm, 20mm Nagler in a f/4.9 DOB?
I am considering getting one, but have yet to get to try one out to see if it makes any real improvemnet or not.
Floyd

Bill,
Thanks for the info. I was hoping to get to try out a Paracorr at Mt Pinos, but so far no luck. Not really sure it would be worth the money at this time.
I don't see much coma in my EPs as it is now, but I am sure the Paracorr make it even better, just not sure if it is enough to justify the cost.
Floyd