| The Coronado PST double-stack consists of a 400mm focal length 40mm aperture f/10 refractor with a very narrow passband “double-stack” hydrogen-alpha solar filter. The filter uses dual etalons in a double stack configuration (40mm external and 20mm internal) to provide a very narrow <0.5 Ångstrom passband, centered on the 6562.8 Ångstrom H-Alpha line. The narrow passband width provides maximum contrast and visibility of active regions on the solar disk, although with some loss of faint detail in the prominences when compared to the standard single etalon PST.
The filter is thermally stable, so there is no drifting off the H-Alpha line as the filter heats up during use. The 5mm clear aperture of the blocking filter portion of H-alpha system (built into the diagonal housing) is ideally matched to the focal length of the telescope to give full disk views of the Sun. The scope’s achromatic doublet objective lens is fully multicoated. A thread-in metal lens cover protects the objective lens of the PST.
The scope uses proprietary internal optical focusing (operated by the external focusing knob shown in the product feature image). The scope and focuser are a completely integrated unit, with no external moving or extending parts (focuser drawtubes, etc.) to gather dust or grit during windy daytime observing sessions.
A rotary collar on the optical tube allows you to fine-tune the internal etalon for the sharpest and highest contrast image. Do not confuse this collar with the focusing knob on the rear of the right angle filter housing. The fine-tuning collar has a limited range of motion and can be damaged if you try to force it to turn in a vain attempt to focus the scope.
You can use most 1.25” eyepieces with the PST. To get you started observing, a 20mm (20x) 1.25” Kellner comes as standard equipment. While optically acceptable, most observers eventually will want to replace this economy eyepiece with one of better quality. Either a 12mm (33x), 18mm (22x), or 25mm (16x) Coronado CEMAX eyepiece would be an excellent choice for observing, as they are optimized for high contrast solar viewing of subtle prominence and surface detail.
The PST includes an internal modified Coronado Sol Ranger Sun Finder to make it easy to center the Sun’s image in the eyepiece. You can see the Sol Ranger screen in the product feature image. An optional hard case is available to carry and store the PST. The case uses the snug-fitting die-cut foam that the PST ships in to hold the PST securely. A 1/4”-20 thread tripod adapter socket is built into the base of the filter/diagonal housing of the PST to allow mounting the 15” long x 2.1” wide x 3” high telescope on a photo tripod. You can also install the lightweight (3 lb.) scope onto a piggyback camera adapter that’s mounted on a larger scope for motorized tracking. | 
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