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Category: Energy Rejection Filters
White Light Energy Rejection
Posted on Apr 20, 2011, 10:29 pm Author: Jen Winter

White Light Filters may not be used for Energy Rejection Filters (ERF) with a DayStar bandpass filter. 

We are often asked if a white light filter (including Thousand Oaks, Baader film or similar) may be used in place of the colored glass ERF filter.    Unfortunately, this will not pass any significant light through both filters at the same time.

The white light filter is designed to reflect 99.997% of all wavelengths of light.   That means that it will also reflect 99.997% of Hydrogen Alpha or Calcium light.   Therefore, the amount of light to reach the front of the DayStar will be 0.003% of what reaches the telescope.  Of that only 4-12% of that light will pass.   The result is approximately 0.00012 - 0.00036% of the light which reaches the telescope will pass through both the white light filter and a DayStar filter.  

DayStar is not designed to operate with white light pre-filters.   
Rather, a colored glass filter is an excellent way to reduce or eliminate heat loads on the telescope. 

Colored glass will BLOCK all colors of light below the wavelength it is rated for.   
RG610 is red glass and will block all light below Red in the spectrum (including harmful UV light) 
Y500 is yellow glass and will block all light below Yellow in the spectrum (also including UV light) 

DayStar uses Yellow glass for Energy Rejection today, as it will pass both Red, Hydrogen Alpha light and yellow light from Sodium and Helium lines.   

There is no harm to the owner should a white light filter be added as a pre-filter to a telescope.  It will only block light, not cause damage.

If users are seeking a less expensive means of energy rejection, we suggest learning more about the UV/IR filter applications available to Refractor owners. 

Tagged Keywords: transmission, white light, daystar, filter, ERF, prefilter

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