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The scope’s achromatic doublet lens was created for solar observing by the well-known optical designer Dick Buchroeder. It uses special multi-layer antireflection coatings on all air-glass surfaces to optimize anti-ghosting. The hard, non-degenerating coatings assure a long lifetime of detailed solar observing. The scope delivers diffraction-limited performance and the extremely high contrast needed to see both subtle surface details and the full explosive power of flares and prominences.

The three-piece solar filter consists of a full-aperture 40mm etalon in front of the objective lens, a performance-matched 20mm diameter etalon mounted within the telescope barrel, and a 10mm clear aperture blocking filter in the scope’s 1.25” star diagonal. The filter is thermally stable, so there is no drifting off the H-Alpha line as the filter heats up during use. (Thermal stability is 0.005Å per degree Centigrade.) The 10mm clear aperture of the blocking filter portion of the H-Alpha system built into the star diagonal is matched to the focal length of the telescope to give full disk views of the Sun.

The SolarMax 40 has a manual 1.25” drawtube that extends for rough focusing. A helical focusing ring around the drawtube then provides the appropriate final fine focusing. This method provides enough back focus to allow both visual observing and afocal imaging. The 10mm blocking filter aperture allows you to use a Barlow in front of the SolarMax 40’s blocking filter/diagonal. This makes digital photography easier and allows the use of a binoviewer with the SolarMax.

A T-Max passband tuner is installed between the 40mm external solar filter etalon and the objective lens. This lets you mechanically tilt the filter’s passband off the H-Alpha line to observe Doppler-shifted solar activity. This will let you determine whether Doppler-shifted features, such as flares, are moving towards you or away from you as they leap off the surface of the Sun. This is particularly important with this double-stacked scope as it provides higher visibility of very subtle disk features than the single etalon <0.7 Ångstrom version. For more details, click on the “T-Max” icon above.

You can use most 1.25” eyepieces with the dual etalon Coronado SolarMax 40. Any good quality 50° field Plössl will work well, as a Plössl’s contrast is generally good and their fields are wide and flat. For optimum solar detail, however, consider adding a 12mm (33x), 18mm (22x), or 25mm (16x) Coronado CEMAX eyepiece to your system. These eyepieces use an anti-reflection multicoatings formula that has been optimized for the highest possible contrast during solar viewing of subtle prominence and surface detail. For still higher power views, also consider adding the Coronado CEBAR 2x Barlow to your system. Like the CEMAX eyepieces, its performance and coatings are optimized for solar observing.

A hard carrying case is standard equipment to transport and store the dual etalon SolarMax 40. A 1/4"-20 thread tripod adapter socket is built into the scope’s clamshell ring to allow mounting the lightweight (3 lb.) 16.75" long telescope on a photo tripod, as well as on most altazimuth and equatorial astronomical mounts. An optional Coronado Sol Ranger Sun Finder is available to make it easy to center the Sun’s image in the eyepiece. The Sol Ranger connects to the SolarMax 40’s supplied clamshell scope mounting ring.

The standard single etalon <0.7 Ångstrom version of the SolarMax 40 (#SM40107) can be “double stacked" by adding a second SolarMax 40 filter and T-Max 40 to the front of the existing single etalon scope. However, this factory-matched dual etalon version offers somewhat higher performance at a slightly lower cost than adding a complete second 40mm filter and the appropriate adapters to a single etalon scope at a later date.