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The prefilter rejection ERF has two functions:
E 'can choose between two different types of pre-filters ERF: the standard working with 1/4 lambda and the Deluxe with processing 1/10 lambda.
You can also install Professional irises 16 steel blades (exactly circular profile all openings) to obtain great advantages.
In fact you can adjust the aperture allows you to:
The filters work Daystar efficiently with f / 30 or greater. A nominal focal ratio f / 30 can be achieved by selecting an appropriate filter ERF + barlow so diaphragm tool and extend the focal length if necessary. To calculate the configuration that allows you to use a particular front opening you can use the formula under riporatata but we advise you to contact our technical service highly specialized in H-alpha observations for accurate configuration of the entire system.
Opening ERF filter = [opening of Telescope (mm) x focal ratio x multiplication factor of a possible or rather Powermate Barlow (telecentric optical system)] / 30
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