IR Imaging??

[Merlin66]

http://www.ebay.com/itm/48mm-590nm-IR-Filter-Infrared-Infra-Red-Optical-Grade-Filter-for-Camera-Lens/142076470100?hash=item21146ae354%3A g%3AbIgAAOxyrrpTfrf4

These may be of interest - the 48mm is the standard 2" Astro filter size.

[Atmos]

I wonder what their quality is like.

[Merlin66]

Probably as good as any of the other 2" filters.......