Baader SolarSpectrum Research Grade 0.4x Telecompressor - 2"

Capture the Full Solar Disk: A 0.4x Focal Reduction for f/30 Systems

Baader's Solar Spectrum H-alpha filters achieve their ultra-narrow bandpass by operating within a parallel light beam, typically created by a telecentric system that extends a telescope's focal ratio to f/30. While optically necessary, this long effective focal length often results in a field of view too small to contain the entire solar disk. The 0.4x Telecompressor directly corrects this by converting the f/30 beam to an effective f/12, dramatically widening your field of view and ensuring you can frame the sun in its entirety.

2-Inch Format for H-alpha Imaging: Wider Fields and Shorter Exposures

For solar imagers, the benefits of the 0.4x telecompressor are twofold. By widening the field, it allows webcams and planetary cameras with smaller sensors to capture the full solar disk in a single frame, eliminating the need for complex mosaics. Furthermore, the f-ratio reduction significantly increases image brightness, which in turn reduces the required exposure times—a critical factor for freezing atmospheric turbulence and achieving sharper images of solar granulation and filamentary detail.

Seamless Integration with 2-Inch and T-2 Threads

This telecompressor is designed for direct, secure attachment to the rear of a Solar Spectrum filter housing. It threads into the Baader 2″ Universal Flange (sold separately, #2958240), which attaches to the filter body with four screws. The telecompressor features a standard 2-inch male thread, and its optical path can be adapted using Baader's extensive T-2 accessory system, allowing for rigid, threaded connections to diagonals, extension tubes, and cameras for a flexure-free imaging train.

Choosing Your Reduction: Baader 0.4x vs. the 0.7x Telecompressor

Baader offers two telecompressors for the Solar Spectrum line, and the choice depends on your specific goals. The 0.7x version provides a more moderate focal reduction, making it ideal for observers who want a wider field but also wish to maintain a larger image scale for detailed views of active regions, flares, and prominences.

The 0.4x telecompressor, in contrast, offers the maximum possible field of view. It is the definitive choice for imagers wanting to capture full-disk portraits, for visual observers using long focal length telescopes, or for anyone operating under seeing conditions that don't support very high magnification. If your primary goal is to see the entire solar disk at once, the 0.4x is the correct tool.