Sky-Watcher Heliostar 100mm Hydrogen-a Solar Telescope

The Sky-Watcher Heliostar 100mm H-alpha Solar Telescope is a purpose-built instrument for observing and imaging the Sun in the narrow H-alpha wavelength. Unlike a conventional white-light solar telescope, it isolates light around the 656.3nm H-alpha emission line, revealing dynamic features in the Sun’s chromosphere including prominences, filaments, active regions, plage, sunspots and solar flares.

At the heart of the Heliostar 100 is a 100mm achromatic doublet with a 760mm focal length and f/7.6 focal ratio. The relatively large aperture provides a high level of image resolution for solar observing and imaging, while the 760mm focal length provides useful image scale without making the telescope excessively long.

The telescope uses Sky-Watcher’s Solis Etalon Technology with an H-alpha bandpass specified by the manufacturer as <0.5 Å. The integrated Trifid Tuner applies mechanical pressure to the etalon plates, allowing the H-alpha system to be tuned to the desired wavelength. This is particularly useful when optimising the view of different solar features.

Focusing is handled by a 2.8-inch dual-speed Rack and Pinion focuser, providing both coarse and fine adjustment. The generous focuser size also makes the Heliostar 100 well suited to solar imaging setups.

For safe visual observing, the telescope is supplied with a dedicated diagonal incorporating a 20mm blocking filter. Sky-Watcher specifically states that this blocking-filter diagonal is part of the telescope’s safety system and that the telescope should not be used with another type of diagonal. The package also includes a 22mm 70° 1.25″ eyepiece, giving approximately 34.5× magnification with the supplied eyepiece.

The Heliostar 100 also includes an integrated solar finder, mounting rings, V-style dovetail, carry handle, clip-on Sun shade, 2″ eyepiece adapter and hard-shell carrying case. At approximately 6.0kg, it is a substantially larger instrument than the Heliostar 76mm, so a suitably stable mount is required. Sky-Watcher specifically highlights the Wave 100i as a matching mount option.

Important: This is a dedicated solar telescope. It must only be used with its supplied solar-filtering components correctly installed. Never point the telescope at the Sun without the complete, specified solar optical system in place, as incorrect use can cause serious and permanent eye damage. Sky-Watcher states that the Heliostar 100 is individually tested for safe solar viewing and has been lab tested in the United States to meet ISO 12312-2.