LS50C — Compact Double Stack Filter The double-stack upgrade designed specifically for the Lunt LS50THa 50mm solar telescope series. Now with new-generation etalons — every unit individually tested on Lunt's precision metrology equipment. Every specification is verified, not estimated. The LS50C is a compact double-stack filter made specifically for the Lunt LS50THa 50mm dedicated solar telescope series. It threads directly onto the front of the LS50THa OTA in seconds — no tools, no factory visit — adding a second 0.35Å tilt-tuned etalon to the optical path and reducing combined system bandpass to ~0.30Å when used with current LS50THa telescopes. The compact form factor is the defining characteristic of the LS50C. It is designed to maintain the LS50THa's grab-and-go character — the total system with the DS filter in place remains compact and manageable on any Vixen-compatible mount or photo tripod. At ~0.30Å combined bandpass the chromospheric contrast improvement over single-stack is immediately and dramatically visible. Surface structure that single-stack views render as texture becomes resolved detail. Plage regions separate from the chromospheric background. Filaments show dark cores and complex multi-strand architecture. Prominences reveal internal threading from base to tip. Note: A Lunt blocking filter is required for safe operation — the LS50C cannot be used without one. Note on bandpass: Combined system bandpass of ~0.30Å is achieved when paired with current LS50THa telescopes. Future LS50THa instruments with new-generation internal etalons will achieve