Solarscope SF-70 - 70mm 0.7A H-Alpha Solar Filter - UNAVAILABLE -

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Solarscope SF-70 - 70mm 0.7A H-Alpha Solar Filter - UNAVAILABLE -

The Solarscope Solar Filter system consists of a front filter unit with a precisely tuned etalon, used together with a secondary blocking filter, which is then mounted onto the user's telescope. The rear mounted secondary blocking filter unit is ideal for use with 2" accessories and convenient for imaging use.

Solarscope filters feature the only conventional ultra-narrow bandwidth Fabry-Perot etalon available to the astronomy community with a full and completely unobstructed aperture. This distinct feature contributes to an image with the highest possible contrast, resolution and definition, for both visual and photographic purposes. The filters- full aperture is only made possible by using the very high optical fabrication skills, time and care normally associated with the manufacture of a high quality, conventional Fabry-Perot etalon.

The basis of the Solarscope etalon is a matched pair of ultra fine pitch-polished, accurately figured ?/100 fused silica plates, with partially reflective, low absorption coatings for 656.28nm on the front faces and anti-reflector coatings on the back faces. The spacers are cut from low thermal expansion material, polished and figured to high levels of surface flatness and parallelism.

The etalon assembly has optically contacted spacer pieces of very precise thickness, uniformly arranged around the etalon plate periphery to provide maximum rigidity and stability for the air gap. When the etalon contacting procedure is complete, the tuned etalon assembly is resiliently mounted into a cell designed to afford shock protection and freedom from stress.

The Solarscope H-alpha filter is a conventional ultra narrow bandwidth 0.7??ngstrom Fabry-Perot air spaced etalon precisely tuned at 656.28nm, the H-alpha line. This is an important emission line for solar observation, as the Sunƒ???????????s surface layer contains a high proportion of Hydrogen. The H-alpha filter allows safe observation of the entire solar disc, providing superb views of prominences, chromosphere and surface detail such as sunspots, plages, flares, filaments and granulation.

The unique internal tilt mechanism designed by Solarscope, allows the etalon cell to be adjusted independently within the front filter unit whilst observing. In order to fine tune and optimize the ultra narrow filter 0.7??ngstrom bandpass, the etalon can be tilted up to 0.4??? using the knurled adjustment screw on the filter body. When flares and coronal mass ejections occur, they can sometimes travel with such high velocity towards the observer that their wavelength is Doppler shifted down spectrum. Use of the etalon tilt facility also enables observation of these events to be improved.

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, 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.


  • Compact and portable, the SF-70 is supplied in a carrying case with recessed component slots and generous padding for protection.
  • Very easy to set up and use, ideal for educational purposes.
  • Suitable for visual, photographic and CCD imaging purposes.
  • The Fabry-Perot etalon 0.7 angstrom ultra narrow bandwidth transmission, together with completely unobstructed 70 mm apertures ensure high resolution surface detail, contrast and stunning H-alpha views of the entire solar disc and limb prominences.
  • Etalon internal fine-tune tilt adjustment provided to optimize contrast and image resolution or to view Doppler-shifted features.
  • High quality optics and instrument components.
  • Traditional Laser optic fabrication, Fabry-Perot etalon polishing and optical surface figuring skills.
  • Blocking Filter unit has a 2" tube mount with 20mm aperture secondary blocking filter mounted in a pre-set tilt cell. The unit is ideal for use with 2" accessories.
  • For telescopes with 1-1/4" tube facility, a right-angled 1-1/4" diagonal assembly is provided. Comes with a 15mm aperture secondary blocking filter mounted in a pre-set tilt adjustment cell.
  • Supplied with 2" to 1-1/4" reducing adapter and unit protective end caps.


  • Single Filter System: SF-70
  • Full Aperture: 70mm
  • Operating Wavelength: 656.28nm (H-alpha)
  • Etalon Coating: Ultra hard multi-layer dielectric reflector
  • Anti-Reflector Coating: Ultra hard multi-layer dielectric AR
  • Transmission: 0.7A Bandwidth with fine tune tilt
  • Thermal Stability: <1A/200???C

Image shows solar filter on a Borg 77. Scope and accessories sold separately.


Aperture75 mm (3")
Emission LineAlpha
Optimized Forf/30 or Under
Tuner IncludedYes