Chroma LRGB Filter Set

Four-Filter LRGB Design: Capturing True Astronomical Color

This four-filter set is the standard for creating full-color astronomical images with a monochrome camera. The process involves capturing detailed structural data through the broadband Luminance filter, then gathering color information through separate Red, Green, and Blue filters. Combining these exposures reveals the true, natural coloration of galaxies, reflection nebulae, and star clusters.

Chroma's design ensures sharp cutoffs and high transmission within each passband, effectively separating the spectrum for accurate color synthesis. The result is natural, well-balanced color from a monochrome camera.

Professional-Grade Construction: 3.0mm Parfocal Substrates

All filters in this set are built on a single, non-laminated substrate of glass with a thickness of 3.0 mm. This uniform thickness makes the set parfocal, meaning you can switch between Luminance, Red, Green, and Blue filters with little or no refocusing, saving critical time during an imaging session.

The filters feature durable, sputtered hard coatings that withstand humidity changes and extreme temperature fluxes. With primary coatings on the front and anti-reflection coatings on the rear, internal reflections and ghosting on bright stars are suppressed. Transmitted wavefront is better than 0.25 waves/inch.

Sizing for Your System: From 1.25" to 50mm Unmounted

To prevent vignetting, the filter must be large enough to accommodate the full light cone from your telescope as it reaches the sensor. This Chroma LRGB set is available in multiple sizes to match your specific imaging train, from small planetary cameras to large full-frame sensors.

• 1.25" and 31mm: Typically suit smaller sensors, up to about the Four Thirds format, depending on the telescope's focal ratio. The 1.25" version is mounted in a standard M28.5x0.6 cell.
• 2" and 36mm: Typically suit APS-C class sensors, with a larger clear aperture than the smaller sizes. The 2" version uses a standard M48x0.75 thread.
• 50mm Round & 50x50mm Square: Typically needed for full-frame class sensors, especially in faster optical systems.

LRGB vs. Narrowband: Choosing the Right Tool for the Target

An LRGB filter set is the essential tool for capturing "broadband" targets, which emit light across the entire visible spectrum. This includes galaxies, star clusters, and reflection nebulae. It captures the object's natural color as your eye would perceive it, if it were sensitive enough.

Narrowband filters (like H-alpha, OIII, and SII) are used for emission nebulae, which radiate at very specific wavelengths of light. While you can image emission nebulae with an LRGB set, the signal will be faint against the background skyglow. For targets like the Orion Nebula (M42) or the North American Nebula (NGC 7000), narrowband filters provide much higher contrast and reveal more structural detail. Many advanced imagers combine LRGB data for natural star color with narrowband data for nebular detail.