Sky-Watcher Heliostar 76Hα Hydrogen Alpha Solar OTA

Due in February!

Solar Maximum is now happening - it's the perfect time to explore the ever changing featured on our nearest star.

The Sky-Watcher Heliostar 76Hα is a specialized prominence telescope designed with advanced safety features to protect the observer’s eyes. It incorporates multiple technologies, including an infrared thermal reflection film to effectively block heat and a dedicated ultraviolet (UV) filter to eliminate harmful rays. These features work in tandem to minimize stray light, ensuring a safe and enhanced viewing experience.

The Sky-Watcher Heliostar 76Hα is a specialized solar telescope designed for enthusiasts eager to explore the Sun’s dynamic features, particularly solar prominences. With a 76mm aperture and a focal length of 630mm (f/8.3), it offers a balanced combination of portability and detailed solar observation.

Key Features:

• Hydrogen-Alpha Observation: The  Heliostar 76Hα utilizes a combination of front and rear filters to isolate the hydrogen-alpha wavelength at 656.28 nanometers. This narrowband filtering, with a bandwidth of less than 0.5 angstroms, enables observers to view solar prominences and surface details with exceptional clarity.
• Advanced Optical Design: Incorporating multiple technologies to protect the observer’s eye, the telescope features a thermal infrared reflection film, a special heat-blocking filter, and an ultraviolet light-blocking filter. These components work together to eliminate stray light and ensure safe solar viewing.
• Precision Focusing: Equipped with a 2-inch Crayford focuser, the  Heliostar 76Hα allows for smooth and precise focusing adjustments, enhancing the overall observing experience.

The  Sky-Watcher Heliostar 76Hα is an excellent choice for both novice and experienced solar observers, offering a safe and detailed view of the Sun’s dynamic phenomena.

Etalon Filter Technology

At the heart of most Hydrogen Alpha solar telescopes lies the etalon filter, a highly precise optical device that isolates the Hα wavelength from the rest of the Sun’s emitted light. An etalon is a type of interferometer, consisting of two parallel mirrors separated by a precise distance. The etalon works by reflecting light multiple times between the mirrors, selectively allowing only wavelengths that satisfy specific resonance conditions to pass through.

In the case of Hα solar telescopes, the etalon is designed to transmit light at the Hα wavelength while blocking all other wavelengths. The key to the etalon’s performance lies in its ability to tune the wavelength it transmits. This is achieved by adjusting the distance between the mirrors or by slightly tilting the etalon, which changes the interference conditions. This tunability is crucial because the Sun's emission at Hα can shift slightly due to Doppler effects as material moves across the Sun’s surface and atmosphere.

There are two primary types of etalon filters used in solar telescopes: single etalon and double etalon systems.

Single Etalon: A single etalon filter typically has a narrower bandwidth, providing high contrast for detailed solar observations but at the cost of limiting the field of view. This makes single etalon systems well-suited for viewing small, high-contrast features like prominences or filaments.

Double Etalon: A double etalon system uses two etalon filters in tandem to improve the wavelength selectivity, reduce the overall bandwidth, and enhance the contrast and image clarity across a wider field of view. Double etalon systems are preferred for more detailed solar studies because they can offer both a sharper image and better tunability, allowing for a more accurate depiction of solar dynamics.

Solis Etalon Technology: Sky-Watcher's Solis technology allows the Heliostar to achieve a 0.5A bandpass without the costly expense and complexity of a second etalon to achieve the same performance. This allows the observer to obtain detailed images of the solar disk right out of the box without any further expense. 

Trifid Tuner: Inside the Heliostar is Sky-Watcher's Trifid tuning system. This tuner applies physical pressure to the etalon plates allowing the observer to reach the desired Hydrogen-band. The Trifid tuner uses three support veins to provide a secure tuning for the etalon. 

What does Hα mean?

The Sun is mainly composed of hydrogen which it's been busily converting to helium for billions of years and will do for some billions of years to come. Hydrogen gas is energised by the Sun's radiation and emits light on certain wavelength. Hα refers to where one of these wavelengths. 

Viewing the Sun through the Heliostar 76Hα lets you discover the Solar chromosphere which is the outer layer of the Sun's atmosphere in great details.

Rather than looking at the Sun in the intense white light we see with our eyes or via a regular solar filter which reduces the overall intensity of the Sun's light so it can be safely viewed with a telescope, a dedicated Solar telescope reveals such details as prominences on the edge of the Sun's disks,  filaments, sunspots and more. 

As the Sun is such a dynamic environment, what you'll see through this telescope will change from day to day.

Specifications