Astronomik L1 UV-IR Filter 2”. A must have for one shot CCD cameras!!!
Adding the L1 UV-IR filter to my set up has reduced star bloat, increased star color and eliminated the red cast background that accompanies CCD chips because of their high sensitivity in the near IR range. There are three different filters to choose from, L1, L2 and L3. Read the specs for each and purchase the one that best fits your setup.