The OWB filter would usually not be designated as an "astronomical" filter. The intention is to enable converted DSLR cameras (without inbuilt IR-filter) in order to be used for 'terrestrial' photography.
We have re-desgined all of our photographic filters. Since the end of 2008 we are shipping our new "Halo-Free" filters. read more...
The OWB (Original White Balance) filter shifts the complete spectrum of a converted DSLR in such a manner that the camera will not be exclusively usable for astro-photography. Therefore the decision, which in former times had to be made, whether to 'victimize' a DSLR in order to exclusively use it for astronomical tasks or accept the lower sensitivity on the red end of the spectrum it is now a thing of the past and disencumber your purse, too.
The OWB EOS Clip filter fits in all APS-C sized series of cameras from Canon: 20D, 30D, 40D, 50D, 60D, 70D, 7D, 300D, 350D, 400D, 450D, 500D, 550D, 600D, 650D, 700D and it also works with the 1000D, 1100D and 100D..
DSLR cameras which have been converted for astronomical use by removing the inbuilt IR-filter or by substituting it with a filter with greater range for H-alpha, have a white balance that made them unable for 'terrestrial' purpose. The spectral sensitivity of the DSLR will be changed by an OWB-Filter to the former range. In other words: The OWB pretend to be the conventional built-in filter!