Rosette nebula (well, bottom half)

[RobertM]

If they are baader filters then there are OIII and SII (and Hb) to match.  They are not exactly the same band pass but are part of the same set and can be used together.  I have the Baader filters and don't have any problems.  They are part of this set : http://www.teleskop-express.de/shop/product_info.php/language/en/info/p502_Schmalband-Filterset-2----H-Alpha-7nm--H-Beta--O-III--S-II.html.

It doesn't look like someone sold you a lemon, rather that you were misinformed about filter compatibility.

Robert

[Carole]

Thanks Robert, those were 2" filters on the link, but I have found some Oiii and Sii Baader filters at 8.5 nm so hopefully they will be close enough.  Thanks, that has put my mind at rest.

Carole

[Fay]

i also have never heard of that problem