Astrodon Tru-Balance Gen 2 - I-Series - LRGB 50mm Round Unmounted Filter Set
Astrodon Tru-Balance RGB filters have revolutionized CCD imaging. Their popularity is due to ease-of-use, high optical throughput and great resulting color for galaxies, star clusters and nebulae. There are two varieties of Tru-Balance filters - E-Series and I-Series.
I-Series filters are designed to approximately equalize the flux of Kodak's Interline 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%. This can never be perfect, but it does allow you to take equal time exposures for your RGB data and also just one corresponding dark exposure time.
Introducing Generation 2 True-Balance filters (LRGB2) in April, 2008 in all sizes. This is the first change in Astrodon filter design and fabrication since their inception. Astrodon listened to your requests!
Astrodon filters are known for being parfocal on most systems. The new thickness tolerance of +/-0.025mm (25 microns) for Generation 2 LRGB fitlers is a factor of 2 better than Gerneration 1 filters, and should be parfocal for systems down to f/3.5, IF your optical system is well color corrected. Please see the article on Parfocal and the Critical Focus Zone. We have reduced the UV contribution in the lumincance and blue filters for this reason to reduce star bloat The Clear (no near-IR blocking) may produce bloated stars if your optical system has poor near-IR focus. Use the near-IR-blocked Luminance filter in this case. The Clear filter is likely a better choice for reflectors, such as Ritchey-Cretiens, rather than refractors or camera lenses.
Halo elimination results from a pioneering design that places both the bandpass layer and the blocking layer on one side of the 1/4-wave substrate and a high performance anti-reflective coating on the other side. As a result there is virtually no internal reflection between these surfaces that can cause halos around bright stars in other filter brands. M45 is one of the most demanding of targets that often leads to halos around bright stars. Tony Hallas' image of M45 had NO touch-up or processing out of halos on those super bright stars. Not necessary with Generation 2 filters. There were NO halos to start with!
Generation 2 LRGB E-Series Testimonial from Tony Hallas (note - the I-Series uses the same high efficiency blue and luminance filters as the E-Series) :
"I would like to take a minute to comment on the 50mm Gen II filters that I have installed in my Apogee 16803 camera.
These filters set a new bar for performance ... they have a huge color gamut and best of all, there isn't a trace of reflection even when shooting 15 minute subs at the Pleiades. The total color response can be seen in the M33 sample ... note the abundant HII regions, the strong blue response, and the brilliant yellow of the star. The superior color response isn't subtle ... it's obvious ... and all this with LRGB ... no narrow band needed/ These filters are a joy to work with. Major kudos!" --Tony Hallas
Astrodon Tru-Balance Generation 2 Filter Features
- RGB filters designed to produce true color for galaxies and stars based upon a G2V (sun-like star) white point.
- Equal exposure time for each RGB filter leads to equal fluxes and equal color weights (combine ~ 1:1:1).
- Correct blue-green color for OIII in plane-tary nebula with 1:1:1 RGB color weights for correct star color.
- Two LRGB designs; E-Series for full-frame, and I-Series for Interline CCDs.
- Deep red filter in E-Series brings out HII regions in galaxies and better definition of H-alpha in emission nebula.
- All filters transmit an amazing 98% in their passbands for the highest perform-ance available.
- All filters are UV– and NIR-blocked. No extra filters are needed.
- Breakthrough design eliminates halos around bright stars.
- Hardest optical coatings on 1/4-wave fused silica substrates for durability.
- Coatings extend to the edge (no uncoated rims that need to be blocked) and no edge-sealing is required.
- Light pollution suppression included in the design.
Astrodon Product Number: LRGB2-I50R