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A Precision Interference Filter for  EBAY Astronomers that selectively passes the 396.0 nm Ca H line. This is new technology, with Dual Magnetron Reactive Sputtering. The films are lower in Temperature coefficient by a factor of 10, resulting in minimal thermal drift. Sputtered refractory oxides of Niobium and Silicon result in nearly unity transmission. Fully blocked filter with visible and NIR background attenuated to OD5+++.  This filter is intended for solar flare and corona photography, Specifically produced for EBAY. 

The filter comes as with high degree blocking elements that attenuate the longer wavelengths to an average of OD 8 and a minimum of OD 5.0. The assembled filter has a dielectric reflective surface coating to reflect 99.99% of the visible light, while transmitting 90+% of the near UV Additional MDM filter is included to provide Far IR reflectivity of 99+% to allow use in Larger Aperture systems. All components are mounted in a standard 28mm or 1.25" Eyepiece ring. The filter will be supplied with specific passband peak at 25 C, and correction table for wavelength at potential temperatures. 

Specifications follow:

Central Pass Wavelengths 396.9nm+-0.05nm (May require tilting or positioning in appropriate system speed location to peak transmitted line) at temperature between 15 and 40 C. (Temp coefficient of this filter is 0.002 nm/ C; note that this is 1/10 the coefficient of prior offers.) Safe operating range from -250 to + 200C. Minimum assembled transmission of 30%. FWHM of 2 Angstroms, Measured in corrected f8 at < 0.3nm.

Each of the filter elements  is optimized to pass at 396 while highly attenuating longer wavelength light to 10e++5. Primary Dielectric ERF Blocking filter in series with MDM FIR Filter allows typical 60% of UVA transmission of the CaH band. Half Power Bandwidth (in modeled theory) is < 0.2nm or 2 Angstroms. I believe this is the narrowest, and highest transmission Calcium H filter offered!! 

Background attenuation OD 7+, UV to 20,000nm as a single filter. 

Size; 25mm in 28mm (1 1/4') eyepiece holder. Filter has minimal TWD.

Note that this filter has a dielectric EFR included with 99.99+% R of Visible (I will list the ERF as a stand alone unit.), Additionally included is an MDM interference filter to replace absorbing glass to control the Near and Far IR..

Filter supplied with actual spectral data. Curve one is the filter free spectral range at expanded scale to OD 5.0. The second curve is the measured performance of the individual element through the narrow region around the Calcium UV llines.

Note, a good general reference:

For more information on filter and system relationships check out Omega Listings such as :

If you don't find your need, try a wild card search. Go to my BJOMEJAG EBUYER STORE and add an * or so to the description, to get close matches.

For a most comprehensive assortment of filter solutions, follow the link at my store, under "Technical Data" to the Omega 'Build A Filter' tool. Millions of potential matches are available. Prices are very reasonable if you indicate "cosmetic seconds acceptable".

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On Nov-25-12 at 12:18:28 PST, seller added the following information: