I purchased two 0.1nm Ha filters from Omega filters (ebay store) thinking I'd try to put together a DIY Ha scope along the lines of Groski and others. They've laid idle for several months and I think I have to admit I'm not going to get around to this project anytime soon.
Each filter is the thin "blue" version. One has a peak just inside 656.3nm and the other a peak at around 657.0. They would require a tilt system, ERF, and a filter to exclude blue light to function properly.
Together they cost me $220, asking $150.
I'll add photos later - I have them but my computer isn't reading the camera's disk.
Links: http://www.ebay.com/itm/Optical-Interfe ... 232538a706
http://bjomejag.squarespace.com/journal ... scope.html
http://solarchat.natca.net/index.php/en ... ay-filters