ZWO LRGB Filter Set for Mono Cameras (1.25" or 2")

True-color galaxies, clusters and star fields from a mono camera

The ZWO LRGB Filter Set is four filters, luminance, red, green and blue, for building full-color images with a monochrome camera. You shoot each filter in turn, usually through a filter wheel, and combine them in processing: luminance carries the fine detail and RGB adds the color. We carry the set in 1.25" (M28.5 threads) for small-sensor cameras and 2" (M48 threads) for APS-C and full-frame sensors. ZWO also makes 31mm and 36mm unmounted versions, which we don't stock.

Key specs: L, R, G and B filters · over 92% passband transmission · 700-1100nm infrared blocked · RGB weights about 1:1:1 · 1/4-wave polished, multilayer anti-reflection coated · 1.25" (1.9mm glass) or 2" (1.85mm glass) mounted

What you can image with it

• Galaxies: Andromeda (M31), the Whirlpool (M51), Bode's and the Cigar (M81 and M82), the Pinwheel (M101) and the Leo Triplet, with luminance bringing out spiral arms and dust lanes.
• Star clusters: the Pleiades (M45), the Double Cluster and globulars like M13 in Hercules, where star color is the whole point.
• Reflection and dark nebulae: the Iris Nebula, the dusty areas around Rho Ophiuchi and the blue reflection nebulae of the Pleiades, which narrowband filters can't record.
• Natural star color for narrowband images: a short set of RGB frames gives true-color stars to blend into an SHO or HOO nebula image.

How it works

Each color filter passes about a third of the visible spectrum: blue from roughly 400 to 500nm, green from about 500 to 575nm and red from about 590 to 700nm, as ZWO's transmission curve shows. The luminance filter passes the whole 400-700nm range at once. Because luminance collects light three times faster than any one color, a common plan is to spend about half your time on L and split the rest between R, G and B, then combine them as an LRGB image.

ZWO keeps the glass thickness tightly controlled (1.9 ±0.03mm on the 1.25" filters) so focus shifts little between filters. Small offsets still happen, especially with refractors, so an electronic focuser and filter offsets in your capture software are worth setting up.

Which size do you need?

Match the filter size to your camera's sensor and filter wheel. ZWO pairs its 1.25" and 31mm wheels with 4/3-inch, 1-inch and smaller cameras, recommends 2" or 36mm filters for APS-C, and only 2" for full frame.

• 1.25" (up to about a 1-inch sensor): the ASI533MM Pro, ASI585MM, ASI678MM and ASI174MM Mini. Use it in the EFW 5x1.25" or EFW 8x1.25".
• 2" (APS-C and full frame): the ASI2600MM Pro, ASI2600MM Air and ASI6200MM Pro. The ASI585MM Air also needs 2" filters because its guide sensor shares the light path. Use them in the EFW 5x2" or EFW 7x2".
• 36mm (4/3-inch and APS-C): for the EFW 7x36mm, we carry the Optolong LRGB set in 36mm unmounted.

Using it in Colorado

Broadband filters collect skyglow along with the target, so from Denver-area backyards LRGB works best on moonless nights and on brighter galaxies and clusters. A trip to darker skies, such as the Westcliffe and Silver Cliff area or the eastern plains, makes the biggest difference for faint galaxies. Many Front Range imagers shoot narrowband from home and save LRGB nights for darker sites.

What to add for the best results

• A mono camera (required): the ZWO ASI533MM Pro pairs with the 1.25" set; the ASI2600MM Pro pairs with the 2" set.
• A filter wheel: the EFW 8x1.25" holds this set plus SHO with one slot spare; for 2", the EFW 7x2" does the same.
• ZWO 7nm SHO narrowband set (1.25" or 2"): adds hydrogen-alpha, OIII and SII for emission nebulae under city skies.
• ASIAIR Plus: runs filter sequences and autofocus from your phone or tablet.
• ZWO EAFN electronic focuser: refocuses automatically when the filter changes or the temperature drops.

Compare color filter options for mono cameras

See all astronomy filters and filter wheels and drawers.

What's in the box

• ZWO luminance filter
• ZWO red filter
• ZWO green filter
• ZWO blue filter

All four come in the size you choose (1.25" or 2" mounted). The 1.25" set comes in a four-slot plastic storage case. The camera and filter wheel are sold separately.

ZWO LRGB Filters FAQ

Do I need LRGB filters with a color camera?

No. A one-shot color camera already has red, green and blue filters built onto its sensor. LRGB filters are for monochrome cameras, which trade convenience for sharper detail and more flexibility.

1.25" or 2"?

Match the filter to your sensor. 1.25" covers sensors up to about 1 inch, like the ASI533MM Pro and ASI585MM. APS-C and full-frame sensors, like the ASI2600MM Pro and ASI6200MM Pro, need 2".

Which side faces the telescope?

ZWO marks it by coating: the side with the multilayer coating (a blue reflection at the edge) faces the telescope, and the side with the anti-reflection coating (a yellow-green reflection) faces the camera.

Are the filters parfocal?

Close. The glass is held to a tight thickness so focus changes are small, but we still recommend autofocus or per-filter focus offsets, especially with refractors.

Will these filters help with light pollution?

A little. The gap between green and red skips the main sodium and mercury streetlight lines, but broadband filters still let most skyglow through. For nebulae under bright skies, narrowband filters do far more.

How should I split my imaging time?

A common starting point is about half the total on luminance and the rest divided evenly among red, green and blue. Under bright skies some imagers skip L and shoot RGB only.

Specifications