ZWO SII 7nm NARROWBAND FILTER GEOPTIK13 has a 3/8" female thread

has a 3/8" female thread

which is useful for telescopes with short backfocus such as fast Newtonians

The ZWO off-axis guider uses a prism that deviates part of the light from the main telescope and redirects it to the guiding camera

25mm (saddle only)

SKU CE-94241

ZWO SII 7nm NARROWBAND FILTER GEOPTIK13 has a 3/8" female threadThe ZWO 7nm Sulphur II narrowband filter enhances the contrast of emission and planetary nebulae. These peculiar nebulae emit light only in specific wavelengths (H; OIII; SII) and the narrowband filters have the property to reject all light outside these bands. The passing band or "window" of these filters is 7nm wide. Considering that the visible light spectrum is between 380nm and 740nm, a 7nm filter would block 98% of the unwanted light. As a