Lunt LS100MT Modular Solar Telescope - Pressure Tuned

Optical Design and Nighttime Performance

The LS100MT is based on a 100 mm FPL-53 ED doublet objective with a focal length of 700 mm at f/7. This configuration delivers excellent chromatic correction, increased resolving power, and high contrast for both visual observing and imaging. When configured for nighttime use, the LS100MT functions as a true apochromatic refractor suitable for lunar, planetary, and deep-sky observation. The longer focal length provides a more favorable image scale for high-resolution planetary imaging and detailed visual work.

Hydrogen-Alpha Etalon System

For solar observing, the LS100MT integrates an internal Fabry-Pérot hydrogen-alpha etalon with a typical bandpass of less than 0.65 angstrom. This narrow spectral window isolates the hydrogen-alpha wavelength at 656.28 nm, revealing fine chromospheric structures such as filaments, prominences, plages, and active regions. The internal etalon design ensures long-term stability and protects critical optical components from environmental and thermal influences.

True Doppler Pressure Tuning Technology

The LS100MT employs Lunt’s Internal Pressure Tuning system to precisely align the etalon to the hydrogen-alpha wavelength. By varying the internal air pressure inside a sealed chamber, the refractive index of the air is adjusted without mechanical tilt. This approach produces uniform contrast across the entire solar disk and minimizes field-dependent sweet spots. Pressure tuning also enables true Doppler shifting, allowing observers to tune on and off band to study velocity-dependent solar features such as filament structure and prominence dynamics.

Blocking Filter Options and Image Circle

The blocking filter determines the illuminated image circle and overall system suitability for visual observing and imaging. Due to the increased aperture and resolving power of the LS100MT, proper blocking filter selection is especially important.

• B1200 (12mm): Suitable for visual observing and full-disk solar views.
• B1800 (18mm): Recommended for imaging, binoviewers, and larger-format sensors.
• B3400 (34mm): Ideal for advanced imaging with large-format sensors, mosaics, and maximum fully illuminated field.

Modular Architecture and Multi-Wavelength Capability

As part of Lunt’s MT series, the LS100MT features a fully modular architecture. In its standard configuration, it operates as a dedicated hydrogen-alpha solar telescope. The H-alpha module can be completely removed, converting the instrument into a 100 mm ED apochromatic refractor for nighttime astronomy in minutes. The system is compatible with Lunt Calcium-K modules and white-light Herschel wedges, offering a flexible and future-proof platform for multi-wavelength solar research.

Mechanical Design and Build Quality

The LS100MT is constructed to observatory-grade standards and features a heavy-duty dual-speed rack-and-pinion focuser with a 10:1 fine-focus reduction for precise focusing at high magnifications. The optical tube is mounted in CNC-machined rings and includes a dedicated solar finder handle for safe alignment. The telescope is supplied in a custom-fitted, aluminum finished hard case, ensuring durability and long-term reliability under demanding solar observing conditions.