About this product
Part Number: LRGB2_E31R
Astrodon LRGB Gen2 E-Series Tru-Balance filters have revolutionised CCD imaging. Their popularity is due to their ease-of-use, high optical throughput and great resulting colours for galaxies, star clusters and nebulae.
E-Series filters are designed to approximately equalise the flux of red-sensitive full-frame (formerly Kodak E-Series) CCD detectors, including compensation for the solar photon flux. This means that your RGB colour combine weights will be approximately 1:1:1 within perhaps 10% for equal length exposures. This can never be perfect, but it does allow you to take one exposure time for all of your RGB data and therefore, only just one corresponding dark exposure time. Again, this saves you precious imaging time and thus, simplifies your imaging.
The E-Series filters were originally designed for cameras containing the full-frame KAF8300, KAF3200, KAF6303, KAF16803 sensors. They are also a good choice for the latest Sony and back-thinned sensors and CMOS sensors. The E-Series red filter is a deep red filter about 60 nm wide, which excludes much of the light pollution from high pressure sodium street lamps. Other filter suppliers try to “force fit” their orange filter (designed for the interline KAI11000, KAI2000 sensors) for use with these full-frame sensors. Their orange filter is about twice as wide spectrally as our deep red filter. As a result, their orange filter tends to “wash out” HII regions in galaxies and detail in nebula. Their blue and green colour weights are no longer balanced and as a result, the OIII colour in planetary nebula is skewed strongly toward blue, rather than the correct teal colour. These are the reasons why Astrodon designed E- and I-Series filters for these different classes of cameras for optimum results.
- Set includes Luminance (NIR/UV-blocked colourless), Red, Green and Blue filters
- 1.25″ mounted, 31, 36, 49.7 mm dia, 49.7 mm square (36 mm filters will not exceed 36.1 mm dia.)
- 3 +/-0.025 mm single 1/4-wave fused silica substrate before coating
- 30 arcsec parallelism
- ~1:1:1 colour combine weights for G2V white-point for Full-Frame (E) detectors
- Best choice for back-thinned and Sony detectors
- Equal RGB exposures and one dark time
- Better colour separation (see spectra)
- Better colour rendition for galaxies based upon colour theory
- Significant reflection and star halo reduction
- Enhanced contrast for HII regions in galaxies due to narrower red (not orange) filter
- Spectral “gap” between green and red filters to minimise effect of light pollution, especially from high pressure sodium street lamps
- Highest efficiency blue filter with less UV
- Correct “teal” OIII colour for planetary nebula (OIII signal >97% in blue and green)
- Parfocal with Astrodon‘s high-performance narrowband, Clear and Near-IR Luminance filters
- Ultra-hard and durable sputtered coatings coated to the edge of each filter
- Proudly made in the U.S.A.
Notice that Astrodon filters are coated to the edge. Other filters leave an uncoated “rim” (see below) near the edge that must be blocked by a mask or the design of the filter wheel. Their approach minimises stray light from polluting your image.
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