Use the Alpine Astronomical Baader Male M42x1 to Male T-2 Adapter to convert M42x1 male threads, that are popular on many Pentax telescopes, to a standard T-2 size. As part of the T-2 Astro modular accessory system, this adapter allows you to use all of the components in the line-including rings, extension tubes, filter holders, and other adapters-to build custom imaging rigs.