Dette fra en spændende artikel hos The British Astronomical Association
Currently (i.e. January 2018) UBVRI filters can be bought from the following companies:
• Andover Corporation: https://www.andovercorp.com/products/as ... ers/ubvri/
• Astrodon: http://astrodon.com/store/p10/Astrodon_ ... lters.html
• Baader Planetarium: http://www.baader-planetarium.com/en/fi ... etary.html
• Chroma: https://www.chroma.com/products/single- ... /astronomy
• Custom Scientific: http://www.customscientific.com/astronomy.html
• Optec Inc.: https://optecinc.com/astronomy/catalog/ ... wheels.htm
Dielectric coatings are used by some manufacturers to better match the UBVRI prescriptions. However, Bessell (2005) and Majewski (2008) note that, depending on the f/ratio of the telescope, the bandwidth of an interference filter can change across the field of view introducing systematic differences in the photometry.
Any ‘tilting’ of an interference filter will also introduce changes to its transmission characteristics. Baader (2016) outline some other problems that may occur when using interference filters.
Commercial filter sets are designed to be ‘parfocal ’ (i.e., all the same thickness) and to have a high throughput. Even with parfocal filters some minor refocusing may be needed as a result of temperature changes (Baader 2016). Problems have also been encountered with respect to the chemical stability of Schott BG39 and KG3 glasses. In particular the Schott BG39 can develop a haze on its surface. It has been reported that Hydrogen Peroxide will remove this. Another option is to cover these glasses with a clear window.
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