About Solarscope

Solarscope Ltd is situated on the Isle of Man in the British IsIes. The company was founded by Ken Huggett, who has thirty years experience in optical instrument design. Solarscope is based in a modern custom-built factory, for the manufacture of optics to the highest standards. The test room has separate foundations from the main building to eliminate vibration when testing optical surfaces. During the optical fabrication process, surface figure and transmission measurements are carried out using non contact interferometry with specialised analysis software. Solarscope optics and mechanical components are produced by highly skilled opticians, engineers and technicians, many having at least twenty five years experience in the design, manufacture and inspection of high quality Laser optics, Fabry-Perot etalons and optical instrumentation.

Solarscope produce precisely tuned, ultra narrow line width classical Fabry-Perot air spaced etalons for their solar instruments. The etalon consists of a matched pair of ultra fine pitch polished and accurately figured fused silica plates, with partially reflective and low absorption coatings for the desired transmission wavelength. In order to provide the requisite fixed air space, the two etalon plates are skilfully assembled with the use of optically contacted spacers.

In telescopic astronomy, optical filters are often useful for observing objects at specific wavelength bandwidths. A major advantage of Fabry-Perot etalons used as optical filters is their very high throughput at peak resonance and very narrow spectral transmission. The Solarscope optical filter corresponds to the key spectral line of hydrogen, known as the H-alpha line. This is an important emission line used in solar observation, as the Sun's surface layer contains a high proportion of Hydrogen. As a result of the ultra narrow bandwidth transmission of 0.7 angstrom at 656.28nm, the Solarscope H-alpha solar filter allows safe observation of the entire solar disc, providing superb views of prominences and surface detail such as plages, flares, filaments, granulation, etc.

Solarscope produce a dedicated, compact `Solarview 50' telescope and `Solar Filter 50' system. Both products are also available as double stacked, enhanced contrast filters. The `Solar Filter 50' system enables many standard telescopes to be easily converted into an instrument that is ideal for safe H-alpha solar observation. The `Solar Filter 50' unit is mounted onto the front of the user's telescope with a threaded adapter plate. The blocking filter assembly is positioned into the telescope focuser draw tube to complete the system.

Laser optics, Fabry-Perot air spaced etalon and instrumentation have been manufactured continuously on the Isle of Man since 1973. The Isle of Man has now gained worldwide recognition as a centre of excellence in the Laser optic industry and specifically for the manufacture of high quality air spaced, re-entrant, solid, confocal and tuneable Fabry-Perot etalons. Etalon manufacture places extreme demands on a company's optical and coating abilities. Material purity, optical figure, plate parallelism, surface quality, spacer contacting and coating quality is critical to the overall performance of an etalon.

Historical perspective : The Fabry-Perot interferometer consists of two parallel flat semi-transparent mirrors separated by a fixed distance. This arrangement is called an etalon, Charles Fabry and Albert Perot - 1897. Many comprehensive optic textbooks describe the optical interference phenomena and show the basic behaviour of the multiple interference devices known as the Fabry-Perot interferometer. (Fabry 1923; Born & Wolf 1964; Steel 1967; Cook 1971; Hernandez 1986; Vaughan 1989)

Solarscope solar filter specifications :

Safety is paramount, positioned at the front of the Solarscope solar filter is the energy rejection filter (ERF). The ERF is used with other optical blocking elements to suppress ultra violet and infra red wavelengths and also control the brightness of the final image. The combined blocking effect of these elements in the UV and IR are shown below in the Perkin Elmer Lambda 900 spectrophotometer transmission plot. The transmission peak at 600 - 700nm is within the visible spectrum and contains the H-alpha spectral line.

Final suppression of unwanted light and transmission of a single narrow H-alpha spectral line is achieved by the addition of the etalon and secondary filter combination. This is an ultra narrow line width 0.7 angstrom bandpass filter, consisting of a precisely tuned, air spaced Fabry-Perot etalon, used in series with a secondary multi-cavity interference blocking filter. The secondary filter blocks all transmission peaks of the Fabry-Perot etalon, except for a single ultra narrow spectral line centered at 656.28nm, the H-alpha wavelength. Transmission characteristics of the etalon and secondary blocking filter are too narrow to be resolved and shown meaningfully on the above plot.

Solarview 50 telescope

Focal Length :		400mm
Focal Ratio :		f / 8
Objective Lens :		Achromatic doublet
Clear Aperture :		50mm
Operating Wavelength :		656.28nm ( H-alpha )
Coatings :		Ultra Hard multi-layer dielectric partial reflection Ultra Hard multi-layer dielectric antirereflection
Filter Bandwidth :		0.7Å with fine-tune tilt adjustment mechanism
Thermal Stability :		<1Å / 200°C
Eyepiece Tube ID :		1-1/4"
Length :		355mm / 14"
Weight :		1.5 kilos / 3.5 lbs

Solar Filter 50 system

Clear Aperture :		50mm
Operating Wavelength :		656.28nm ( H-alpha )
Coatings :		Ultra Hard multi-layer dielectric partial reflection Ultra Hard multi-layer dielectric antirereflection
Filter Bandwidth :		0.7Å with fine-tune tilt adjustment mechanism
Thermal Stability :		<1Å / 200°C
Adapter Plate :		To suit user's telescope

Solar Filter 50 system blocking filter assemblies

Supplied as standard :		For use with 2" accessories, this assembly has a 20mm aperture blocking filter mounted in pre-set tilt cell. 2" to 1-1/4" reducing adapter is included.
For telescopes with 1-1/4" facility only :		1- 1/4" right angled diagonal assembly, fitted with a 15mm aperture blocking filter mounted in a pre-set tilt cell.