2. BAADER AstroSolar™: Solar Filter Material from Baader Planetarium

This new high-strength polymer solar filter produces a high contrast, scatter-free and diffraction-limited image. To produce this special film, the manufacturer uses a patented high-temperature process, similar to annealing, to eliminate internal strains.The material is then ion implanted and metallized with a tough, color-neutral layer on both sides of the film. This ion implantation/metallization process (also patented), produces a high-contrast film that stands up to considerable abuse, unlike the metallized mylar materials used in virtually every other commercial solar filter today. The coating cannot easily be rubbed off, and in that respect is actually safer than coated glass filters. The material is coated on both sides, even if you find a pinhole on one side, it is likely that the other side is still coated, providing the protection of that single layer. Since it is nearly impossible for any manufacturer to produce filter coating that is absolutely pinhole-free, a few pinholes may be found.

Unlike commercial film and glass filters, Baader's AstroSolar™ will not significantly degrade the imaging capabilities of telescope. Roland Christen of Astro-Physics has checked out samples of this material on a double-pass interferometer and measured a 94% Strehl Ratio when placed flat over a 6" test optic. Compare this to Strehl ratios of 45% for aluminized Mylar and less than 24% for inexpensive glass solar filters.

	BAADER AstroSolar™: ND 5 for visual and ND 3.8 for photography

Performance

This filter produce almost neutral color on the surface, and the black background sky due to the lack of scatter and few, if any, pinholes. The extensive solar granulation all over the surface, as in any high-resolution glass filter was seen. Sunspots showed detail deep within the umbra and the penumbral brushes were so finely resolved, they looked like eyelashes. But what surprised most was that white filamentary faculae all over the sun's surface was seen, not just at the edge.

	Image of The Sun during sunset at LNSO ( 30 Jan 2007) using Baader Astrosolar Filter

This filter is used in many telescope, such as TMB 152, Vixen 80M, Takahashi FSQ 106 and finderscope.

3. Daystar Hydrogen-Alpha Filter: University Series

The University series filtering system is designed for serious research programs requiring full aperture spectral uniformity. Systems are fabricated from the finest optical and filtering components available, manufactured by DayStar.

Professional institutions and advanced observers that employ research quality optical systems are encouraged to consider the filtering power of this top quality product. Available in a 0.80Å to 0.50Å bandpass, The University series is designed to handle any focal length system providing an f/30 beam while delivering full aperture spectral uniformity. The resulting visual observations, CCD images and traditional filtergrams are simply stunning. All filtering elements are thermally tuned by a calibrated precision oven and by varying the etalon temperature the observer is able to optimize contrast and engage in Doppler studies. These precision systems are extremely difficult to produce, and may create a variable delivery schedule.

Technical specification

All DayStar filtering systems are fabricated one at a time. In general, factors such as half-bandwidths and spectral uniformity will govern manufacturing complexity and guide the basis for the cost of each system. The half-bandwidth controls the contrast of features seen on the solar surface. Normal prices feature +/- 1/3 angstrom tuning. Filters incorporating +/- 1.0 angstrom tuning for advanced Doppler studies are available for an additional 10%.

This filter is attached to TMB 152 telescope for high-resolution full disk solar imaging.

	Image of Sunset at LNSO ( 30 Jan 2007) using Daystar H-Alpha Filter 0.5Å Bandpass (University Model). Red false color is applied with this image.

4. Coronado SolarMax 90 Filter

Based on Coronado’s original AS1 series filters, these two-piece filter sets represent over one hundred years of developments in the Fabroy-Peret etalon, most of which have been accomplished by the engineers at Coronado during the past ten years. The AS1 series broke down the barrier that had kept the etalon a relatively obscure filter to the amateur community – Thermal Stability. By adding a central obstruction Coronado has been able to develop a patented, thermally stable, etalon that will work in extreme colds and extreme heats, please thermal stability specs below. While a typical cassegrain has a central obstruction of approximately 35%,- giving an area obstruction of ~12%,- that in the SolarMax filters is only 2.5% to 5.5% depending on the model. This is well within the obstruction generally considered to be completely unnoticeable to image quality, especially on a hi-resolution object like the sun. It does guarantee a thermally stable on band performance every time you set it up.

The SolarMax includes a T-Max de-tuning filter. Some events on the Sun,- notably active flares and coronal mass ejections (CME), are extremely fast moving. If such features occur on the disc of the Sun, their high velocity towards the observer results in their wavelength being Doppler shifted shorter than Ha. If the velocity is high enough, this wavelength could be outside the passband of the filter and the feature would not be observable. The T-Max allows the user to de-tune the SolarMax slightly to bring such phenomena into better visibility

	Coronado SolarMax 90 Filter rear assembly (Coronado)

 

	Coronado BF10 Blocking Filter back assembly (Coronado)

 

This filter is mainly for visual observation of the sun using FSQ-106 telescope.