Filter Wheels & Filter Sets

The "switch from L to R to G to B to Hα to OIII automatically while you sleep" tier — motorised filter wheels (EFWs) and the matched filter sets they hold. Mono setups need an EFW: 5-position for LRGB, 7-position for LRGB + SHO. OSC setups can survive without one but a single filter slot for an L-Ultimate or L-Pro plus a clear/UV-IR-cut is still nice.

For the filters themselves see Light Pollution & Filters; for the cameras the wheel sits in front of see Astro Cameras & Sensors; for the session manager that drives the wheel see Mount & Session Control.

Electronic filter wheels (EFW)

• ★ ★ ZWO EFW (5/7/8 position) — paid (~$280–$450). The market-leading wheel; Mini / 2"/8-pos / 36 mm 7-pos variants. ASCOM/INDI/Alpaca; talks to ASIAIR natively. ZWO ecosystem.
• ★ QHY CFW3 (5/7-position) — paid (~$300–$500). Equivalent. ASCOM/INDI/Alpaca. Slightly thicker back-focus than ZWO.
• ★ Player One Cygnus EFW (7-position) — paid (~$300). Newer; thinner profile; competitive build.
• Touptek EFW — cheaper option; less polished drivers.
• Atik EFW — older European; reliable; smaller community.
• Starlight Xpress — older premium UK; expensive; less common in 2026.

Filter sizes

• 1.25" round — small format cameras (1/2.8", 1/1.8"); cheapest.
• ★ 2" round — APS-C cameras (IMX571 family); the 2026 default. ZWO/QHY/Player One 7-position 2" wheels.
• 31 mm / 36 mm round (unmounted) — slimmer; for 7-position wheels with limited Z-thickness; matched to APS-C.
• 50 mm square — for full-frame (IMX455 / IMX461); expensive; specialty wheels (ZWO 50 mm-7).

Back-focus reality

EFWs add 20–30 mm of back-focus to the camera train. Off-axis guiders, focal reducers, telecompressors all live in this stack — plan it out before buying. Manufacturers publish exact dimensions; tools like astrobin.com and first-light-optics-calculators help.

Filter sets — LRGB

For mono cameras, a baseline LRGB set is required:

• ★ Antlia 36 mm LRGB Pro — paid (~$700 set of 4). Value pick; well-regarded.
• ★ Astrodon Series-E LRGB — paid (~$1500 set). Pro standard; sharper bandpasses; expensive.
• ★ Chroma 50 mm LRGB — paid (~$1800 set). Pro; same league as Astrodon.
• Optolong LRGB-2c — cheaper (~$300 set); for first mono setup.
• Baader LRGB-CCD — paid (~$700); reliable.

Filter sets — SHO narrowband

For mono SHO (Hα / OIII / SII) imaging:

• ★ Antlia 3 nm Pro Set — paid (~$1100 set); 2024 favourite for value.
• Antlia 4.5 nm / 5 nm sets — paid; cheaper.
• ★ Chroma 3-5 nm — paid (~$1500+ each, $4500+ set). Pro standard.
• ★ Astrodon 3 nm / 5 nm — paid (~$1500+ each). Pro.
• Optolong / Player One narrowband sets — paid; ~$700-900 set; value.
• Baader 3.5 / 6.5 nm narrowband — paid; respected.

Filter sets — OSC dual-band

For one-shot color cameras under light pollution, see Light Pollution & Filters. Common picks: Optolong L-Pro, L-eXtreme, L-Ultimate; IDAS NBZ-II; Antlia ALP-T 5 nm.

Calibration / refocus

Each filter has slightly different optical thickness; per-filter focus offsets are now standard in N.I.N.A and Ekos. Configure offsets once, sequencer applies them.

Off-axis guider integration

Many setups use an OAG before the EFW (ZWO OAG-L, Celestron OAG, QHY OAG-S); the prism picks light off ahead of the filter. Saves you from buying a guide-scope; required at long focal lengths.

License / pricing summary

• Hardware paid only — no software cost; drivers are ASCOM/INDI/Alpaca free.
• Wheels: $300–$500 (1.25/2"), $700+ (50 mm full-frame).
• Filter sets: $300 (cheap LRGB) → $1100 (Antlia 3 nm SHO) → $4500+ (Chroma SHO).

Pick this if…

• First mono setup, value LRGB + SHO: ZWO EFW 7×36 mm + Antlia 3 nm Pro set + Antlia LRGB.
• Pro mono setup: QHY CFW3 + Astrodon or Chroma LRGB + 3-5 nm SHO.
• OSC under LP: any single-position drawer + Optolong L-Ultimate or IDAS NBZ.
• Full-frame mono: ZWO/QHY 50 mm square 7-position + Chroma 50 mm.
• Smart-scope owner: the filter wheel is in the scope; not your decision.