The new Sky-Watcher Heliostar 76 is a dedicated 76mm f/8.3 hydrogen-alpha (Hα) solar telescope designed to provide detailed views of the Sun’s dynamic chromosphere. By isolating the Hα wavelength at 656.3 nm, it allows observers to witness solar phenomena with exceptional clarity.
Hydrogen Alpha (Hα) solar telescopes are specialized instruments used to observe the Sun in a specific wavelength of light (656.3 nm) which corresponds to the red line in the Balmer series of hydrogen’s emission spectrum. This wavelength is perfect for studying solar phenomena like prominences, filaments, sunspots, and solar flares in great detail. Unlike standard white-light telescopes, which capture the Sun’s broad spectrum, Hα solar telescopes offer a window into specific solar activity in the chromosphere, a layer of the Sun’s atmosphere located just above the photosphere.
At the heart of the Heliostar 76 is the Solis etalon filter, fine-tuned by the Trifid tuner, achieving a narrow bandpass of less than 0.55 Ångströms. This precise filtration enables high-contrast views of intricate solar features without the need for additional double-stack systems, offering double-stack performance at a single-stack price. The telescope’s achromatic doublet lens is fully multicoated for Hα light, ensuring optimal image quality.
The Heliostar 76 is equipped with a 2-inch dual-speed Crayford focuser, providing smooth and precise focusing adjustments essential for solar observation and imaging. An 11.5mm blocking filter housed in a 1.25-inch diagonal format ensures safety and enhances image contrast. The telescope includes a 20mm 70° eyepiece, delivering 32x magnification, ideal for observing various solar activities.
The telescope also comes with mounting rings, a Vixen-style dovetail, a clip-on sunshade, a smartphone adapter for capturing images, and a hard-shell carrying case for portability. For a comprehensive solar observing setup, the Heliostar 76 is available as a kit with the SolarQuest mount. This mount features HelioFind technology, offering auto-alignment and tracking of the Sun, simplifying the observing experience.
For a comprehensive solar observing setup, the Heliostar 76 is available as a kit with the SolarQuest mount. This mount features HelioFind technology, offering auto-alignment and tracking of the Sun, simplifying the observing experience.
To dive deeper into solar observing, 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.
Sky-Watcher Solis Etalon Technology: Sky-Watcher’s Solis technology allows the Heliostar to achieve a 0.55A bandpass without the 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.
Of course, safety is paramount in solar observation. Each Heliostar 76 unit undergoes individual testing on the Sun to meet ISO 12312-2 safety standards, ensuring secure viewing right out of the box. This rigorous testing process provides users with confidence in the telescope’s safety and performance.
The Sky-Watcher Heliostar 76 specifications include:
– Optical Design: Achromatic
– Intended use: Solar (visual and imaging)
– Lens Coating: H-alpha fully multicoated
– Lens Design: Doublet
– Optical Quality: Diffraction limited (1/4 wave)
– Dawes Limit: 1.52
– Rayleigh Limit: 1.84
– Limiting Magnitude: 11.88
– Magnification: 7x
– Maximum Magnification: 150x
– Magnification with included eyepieces: 32x
– Collimatable Cell: No (Self Aligning Cell)
– Primary Aperture: 76mm
– F/Ratio: 8.3
– Focal Length: 630mm
– Blocking Filter Size: 11.5mm
– Solar Image Size: 6mm
– Bandpass: < 0.55Å
– Focuser Type: Crayford
– Focuser Size : 2″
– Focuser speed: Dual speed
– OTA material: Aluminum
– Optical Tube length: 24″
– Optical Tube weight: 8.4 pounds
– Dovetail type: Vixen dovetail
– Eyepieces: 20mm 70º 1.25″ eyepiece
– Diagonal: 11.5mm 1.25″ H-alpha blocking diagonal
– Camera Adapter: Included
– Sun shade: Included
– Finder: Heliostar solar finder
– Case: Hardshell Carry Case
Intended use Solar (visual & Imaging)
You can learn more about the Sky-Watcher Heliostar 76 here.
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