Test Report -- Optolong L-eXtreme Filter Comparison by Jim Thompson, P.Eng
Optolong L-eXtreme Filter Comparison
by Jim Thompson, P.Eng
Test Report – August 25th, 2020
Introduction:
The light pollution filter market continues to grow, with new offerings being released every couple of months. One of the latest filters to be released is the new L-eXtreme filter from the Chinese company Yulong Optics Co. Ltd. under their Optolong brand. I have a fair amount of experience with Optolong brand filters, all of which started in 2015 with a request directly from Optolong for me to test some of their filters for them*. I was impressed by Optolong’s filters then and I am still impressed today. Because of my history of testing Optolong filters I have a library of their products available to which I can compare any new offerings. This is exactly what I have summarized in this report: a comparison between the new L-eXtreme filter and Optolong’s other filter models. Figure 1 shows the spectral response of the new L-eXtreme filter that was released in North America just this past June. The filter is a refinement of their popular L-eNhance filter, having even narrower pass bands around O-III and Hα.
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Conclusions:
The data collected during this test confirms yet again that a filter with narrow pass bands produces an image with superior contrast on emission-type nebulae. Some other more specific conclusions drawn from this test are:
When compared to other available filters with the same %LT, the Optolong L-Pro filter provides inferior performance under light polluted skies. This observation is true for all filters of this type (i.e. Multi-band), regardless of brand.
In terms of cost per performance the Optolong UHC filter provides a very good value. The filter performs very similar to the Astronomik UHC but at a fraction of the cost.
There is a significant improvement in contrast on emission-type nebulae resulting from the use of the Optolong L-eNhance filter. There is however an issue with white balancing that was not encountered with the other filter models.
Of the six filter configurations tested, the Optolong L-eXtreme filter provided the largest increase in contrast. The increase in contrast relative to the L-eNhance filter was observed to be significant. The filter was also easier to use than the LeNhance due to it being easier to white balance.
