Lunt Double Stack Filter for Lunt 80 mm & 100 mm Universal Telescopes

SFPT — Internal Double Stack Module For Lunt LS80MT & LS100MT Universal Day and Night Telescopes.

Now with new-generation etalons — every unit individually tested on Lunt's precision metrology equipment. Every specification is verified, not estimated.

The SFPT is the internal double-stack module for Lunt's 80mm and 100mm Universal Modular Telescopes. It adds a second precision etalon inside the telescope body, reducing combined system bandpass from 0.45Å single-stack to <0.28Å — without altering the telescope's external dimensions, balance, or night-sky capability.

The improvement in chromospheric contrast at <0.28Å is immediate and significant. Surface detail that single-stack views render as texture separates into discrete structure. Plage boundaries sharpen into defined cellular networks. Filaments reveal dark cores and complex multi-strand architecture. Active regions display the full depth of their magnetic complexity. Prominences show internal threading and flow patterns that single-stack instruments at this aperture simply cannot resolve.

The SFPT is designed for customer installation — no factory return required. It can be purchased at the time of telescope acquisition or at any point thereafter, making the DS upgrade a genuine deferred investment rather than a permanent commitment at point of sale. The module includes dual independent Doppler True tuning knobs — one for each etalon — allowing precise independent control of bandpass position for optimum contrast on any target.

Specifications

• Model: SFPT — Internal Double Stack Module
• Compatible With: LS80MT Universal Telescope | LS100MT Universal Telescope
• Single Stack Bandpass: 0.45Å (telescope internal etalon)
• Module Etalon Bandpass: 0.35Å — individually verified
• DS Combined Bandpass: <0.28Å — SFPT (0.35Å) + MT internal PT (0.45Å)
• Tuning: Dual independent Doppler True Barometric pressure tuning
• Installation: Customer-installed — no factory return required
• Night Sky Use: No impact — internal module does not affect night configuration