Daystar Sol 100mm Dedicated Solar Telescope

A 100mm Integrated H-Alpha Telescope

The Sol 100 is a complete, dedicated solar telescope, not a filter accessory for a nighttime scope. The etalon, 4.3x telecentric barlow, and 18mm blocking filter are all integral components, with the barlow itself forming the focuser drawtube. This clean-sheet design ensures that all optical elements are optimized as a cohesive unit for the 6562.8 Å H-alpha wavelength, with no wobble from components added into a drawtube and no Quark that can be accidentally removed.

This integrated approach delivers inherent safety and simplicity. There are no front filters to mount or separate components to assemble in the correct order. The etalon cup is bolted to the telescope and the barlow and blocker are integral components deep in its structure, so the filter cannot be accidentally removed by a curious child at an outreach event; the Sol 100 can't be unsafe and a telescope at the same time. At 3.6 kg (8 lb) with rings and about 19 inches (489mm) long with the dew shield retracted, it fits into an airline carry-on bag.

Observing the Sun's Chromosphere at 6562.8 Å

By isolating light to the specific 6562.8 Å wavelength of Hydrogen-Alpha, the Sol 100 reveals the Sun's dynamic chromosphere, a layer of gas just above the visible surface. The chromosphere is in constant flux, with visible changes often occurring in just minutes. Each observing session presents a new and unrepeatable view of our home star.

Through the Sol 100, you can directly observe a host of solar phenomena against the backdrop of space or the solar disk itself. Because this is an H-alpha instrument, it is not designed to show photospheric details like granulation, which are features of white-light observing.

• Prominences & Filaments: See vast arcs of plasma extending off the solar limb (prominences) and their dark, ribbon-like counterparts silhouetted against the brighter disk (filaments).
• Active Regions & Plages: Identify bright, magnetically complex areas (plages) that often surround sunspot groups.
• Spicules: Observe the fine, jet-like structures that cover the solar surface, resembling a "burning prairie" at the very edge of the Sun's limb.
• Solar Flares: With luck and timing, witness the intense, abrupt release of energy from an active region as a brilliant, short-lived flare.

Optical System: 1690mm EFL from an Integrated 4.3x Telecentric Barlow

The Sol 100 begins with a 100mm air-spaced achromatic doublet objective lens. To achieve the near-parallel light required by the internal etalon, Daystar integrates a 2-element, 4.3x telecentric barlow directly into the optical path; in fact, the barlow assembly *is* the focuser drawtube. This results in a long 1690mm effective focal length and an f/16.9 focal ratio, ideal for high-resolution views of chromospheric detail.

Despite the long focal length, the custom optical design delivers a 0.75° field of view, wide enough to frame the entire solar disk visually and with APS-C or larger camera sensors. The lenses were prescribed and optimized as a cohesive unit for H-alpha, which achieves the parallelism required for narrow bandpass at the etalon at a faster focal ratio, and the Sol 100 is designed and coated uniquely for the 656nm wavelength.

The Etalon & Filter: A ≤0.5Å Bandwidth for High-Contrast Surface Detail

This Chromosphere model of the Sol 100 is built around a solid etalon with a full width at half maximum (FWHM) bandpass of 0.5Å or narrower. This tight bandpass gives high contrast on surface features like filaments, active regions and plage; Daystar likens the Chromosphere model's surface contrast to a double stack.

The system features a 19mm clear etalon aperture and an integrated 18mm blocking filter. While optimized for surface detail, the 0.5Å bandwidth still provides excellent views of prominences against the blackness of space. The entire filter assembly is a sealed, non-serviceable unit bolted directly to the telescope body for permanent alignment and safety.

Electronic Tuning: PID-Controlled Stability with ±0.5Å Wing Shift

Daystar's proven electronic tuning system uses a PID (Proportional-Integral-Derivative) controller to precisely heat the etalon to its target temperature, locking it onto the 6562.8 Å H-alpha line. Upon connecting the 5V USB power, an LED indicator glows yellow while the system warms up, turning green when it is on-band and ready to observe. This warm-up and settling process takes approximately 5-6 minutes.

A manual tuning knob allows you to "wing shift" the filter's center wavelength by up to ±0.5Å in 0.1Å increments. This is a powerful tool for advanced solar observation:

• Doppler Shift Observation: Tune slightly into the blue wing (counter-clockwise) to better see solar features moving towards you, or into the red wing (clockwise) for features moving away. This can reveal the motion within erupting prominences or filaments.
• Contrast Optimization: Small adjustments can fine-tune contrast for different features across the solar disk.

A red LED indicates a fault such as low voltage.

The Focuser: A 12:1 Dual-Speed Rack & Pinion with Motor Compatibility

The Sol 100 features a Daystar-manufactured 12:1 dual-speed focuser with a helical rack and pinion mechanism. This design provides smooth, precise focus adjustments, which is critical given the long 1690mm effective focal length. A locking brake secures the focuser position for imaging or when using heavy accessories, and stainless steel reduction components ensure long-term durability.

Designed with remote imaging in mind, the focuser is compatible with most third-party focus motors. It provides standard shaft sizes for motor couplers and pre-drilled mounting holes for motor brackets.

• Coarse Focus Shaft: 6mm diameter
• Fine Focus Shaft: 5/32" (4mm) diameter
• Mounting Holes: Three female M4 screw holes are provided for attaching motor brackets.

Visual Observing: Eyepiece Selection for the f/16.9 Optical System

At f/16.9, eyepiece choice is critical for achieving the best possible views. In eyepiece comparisons, zooms and other fast wide-field designs typically performed very badly on Daystar applications; in solar observing, contrast is achieved by control of scattering, which is why Plössl eyepieces are recommended.

For the best performance, look for eyepieces with fully multi-coated optics and blackened lens edges, which further enhance contrast. Plössl eyepieces of 25mm, 32mm and 40mm are recommended. At long focal ratios a high-powered eyepiece can exceed Dawes' limit, so an eyepiece of 32mm or greater gives the best results; higher powers give a fuzzy disk without the ability to focus well.

Solar Imaging: Full-Disk Views with APS-C Sensors and Focal Reducers

The Sol 100's 0.75° field of view and generous focus travel make it a capable imaging platform. It is designed to accommodate everything from a camera mounted flush to the filter housing to a 2" diagonal for visual use. For full-disk imaging, the sensor size determines the required accessories.

• APS-C and Larger Sensors: Can achieve a full-disk image at the native 1690mm focal length.
• 1-inch Format Sensors: Can capture the full disk by using an optional 0.6x focal reducer.
• 1/2-inch Format Sensors: Require a more aggressive 0.33x focal reducer to fit the entire sun in the frame.

Monochrome CCD or CMOS cameras give the best results, as they offer four times the sensitivity and twice the resolution of a color sensor at the monochromatic H-alpha wavelength. To combat interference patterns (Newton's Rings) common in solar imaging, an optional tilt adapter may be necessary. The included Flat Cap diffuser allows you to take calibration frames to correct for dust and uneven field illumination.

Power Requirements: 5V, 1.5A USB Power for Field and Home Use

The etalon's heating and control system requires a USB power source capable of supplying 5V at 1.5A through a micro-B connector. Power must be supplied for the telescope to operate correctly. The package includes a versatile 90-240VAC wall adapter with interchangeable plugs for the US, UK, Europe, and Australia.

For portable field use, the Sol 100 can be powered by a portable USB battery pack, such as Daystar's optional 8-hour battery. It is critical to use a power source that meets the specified requirements. Any other USB power source must be rated for at least 2 amps at 5 volts; computer USB ports and cell phone chargers do not normally support this much power.

Solar Safety: An Integrated System with No User-Serviceable Parts

Used as directed, the solar filters are perfectly safe for observing the Sun. All filtering elements are built-in and cannot be removed without disassembling the telescope, which would void the warranty and could create an unsafe condition. There are no user-serviceable parts inside the telescope.

Always follow proper solar observing safety protocols. Never point the telescope at the Sun without ensuring all components are securely attached. Never look up along the telescope towards the Sun, and do not leave the telescope unattended unless remote monitoring systems are in place. Daystar asks owners to inform guest or novice observers of the special nature of the telescope so as not to imply that telescopic observing of the Sun is safe without proper filtration. Use the supplied power adapter or another USB source rated for at least 2 amps at 5 volts.

Mechanical Design: A 3.6 kg OTA with Integrated Solar Finder

The Sol 100 is engineered to be both robust and portable. The main optical tube has a diameter of 111mm and features a locking, retractable dew shield that brings the total length from 613mm down to 489mm for storage. The OTA alone weighs 3 kg (6.6 lb), and the total weight with the included mounting rings and handle is just 3.6 kg (8 lb).

The included accessories are designed for convenience and immediate use:

• Mounting Rings & Dovetail: The mounting rings attach to a Vixen-style dovetail bar, which also includes a 1/4-20 tapped hole for mounting on a heavy-duty photo tripod.
• Carry Handle & Solar Finder: The carry handle, mounted atop the rings, incorporates a safe and simple solar finder. Simply adjust the telescope's pointing until the bright dot of light is centered on the finder's rear white screen.
• Hard Case: A durable hard case is included for safe transport and storage of the telescope and its primary accessories.

The Sol 100 Chromosphere Model vs. the Prominence Model

Daystar offers the Sol series in two etalon configurations: Chromosphere and Prominence. This listing is for the Chromosphere model, which is the preferred choice for observers focused on high-contrast surface detail.

• Chromosphere Model (≤ 0.5Å): The narrower bandpass of this model excels at revealing fine structures on the solar disk. It darkens the solar disk more effectively, making faint filaments, active region structure, and plage stand out with enhanced contrast. While optimized for the surface, it still provides excellent views of prominences on the limb.
• Prominence Model (> 0.5Å): With a wider bandpass, this model produces a brighter image of the solar limb, which can make very faint or eruptive prominences easier to see. The trade-off is lower contrast on surface details compared to the Chromosphere model.

Daystar likens the Chromosphere model's surface contrast to a double stack, and notes that it still shows prominences.