Used in conjunction with Baader's Solar Spectrum Hydrogen Alpha filters (and possibly other solar filters) to achieve a parallel f/30 optical beam and provide sufficient back-focus for the filter.
This 4x system is suitable for telescopes around f/7.5.
This pre-owned item is unused to the best of our knowledge, having been bought in error by the previous owner. It is in perfect physical and optical condition, with no dust. Supplied with dustcaps fitted to both ends.