We don't display Hepburn Charts because William Hepburn does not permit ANY web site to do that.
To do so is a violation of his terms of use that can be found here [http://www.dxinfocentre.com/tropo.html#USE]
The propagation forecasts on our website are kindly provided, with permission, from Pascal - F5LEN [http://tropo.f5len.org/]
Comparisons between both charts show that they are nearly the same. I wouldn't expect them to be exact since that depends on what weather data they applied their math to at the time.