ZWO SII 7nm NARROWBAND FILTER GEOPTIK13 On the telescope side there

On the telescope side there is an M42 x 0

the UFC Base will be fastened in front of the lens by adding both the S70/SP54 adapter #BA2459134 and the retaining flange #BA2459121

has a 3/8" female thread

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

ZWO SII 7nm NARROWBAND FILTER GEOPTIK13 On the telescope side thereThe 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