Description

Astrodon LRGB Gen2 E-Series Tru-Balance Filter Sets

Astrodon LRGB Gen2 E-Series Tru-Balance Filter Sets have revolutionized CCD imaging. Their popularity is due to their ease-of-use, high optical throughput and great resulting colors for galaxies, star clusters and nebulae.

E-Series filters are designed to approximately equalize 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 color 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.

Features:

  • Set includes Luminance (NIR/UV-blocked colorless), 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 color 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 color separation (see spectra)
  • Better color rendition for galaxies based upon color 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 minimize effect of light pollution, especially from high pressure sodium street lamps (see spectra)
  • Highest efficiency blue filter with less UV
  • Correct “teal” OIII color 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.

The E-Series filters were 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 sensor or any camera with a Progressive Scan Sensor, Front Illuminated or Back Illuminated.  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 color weights are no longer balanced and as a result, the OIII color in planetary nebula is skewed strongly toward blue, rather than the correct teal color. These are the reasons why Astrodon designed E- and I-Series filters for these different classes of cameras for optimum results.

Notice that Astrodon filters are coated to the edge. Other filters leave an uncoated “rim” near the edge that must be blocked by a mask or the design of the filter wheel.  Our approach minimizes stray light from polluting your image.

A common question: Should I get E-Series or I-Series LRGB filters?

The answer is that it depends on your camera sensor. Progressive Scan camera sensors ( including both Front Illuminated and Back Illuminated sensors) use the E-Series LRGB filters. Interline Transfer sensors should use the I-Series LRGB filters. Finding out what type sensor your camera uses can be difficult. This information is not often included in the specifications or even the manual. So it is best to check with the sensor manufacturer. If you absolutely can’t find out, then go with the E-Series and you will be fine.

FLI has put out a convenient list that specifies which type of sensor is in their camera. Since you usually know what sensor is in your camera (and different camera brands often use the same sensor) , this handy list can be used for other camera brands as well. But again, checking with your camera manufacturer and asking if their sensor is Front Illuminated, Back Illuminated, or Interline Transfer is your best bet.