Stacking Starlight

Choosing filters (LRGB vs narrowband) for your camera and sky

Which filters to buy depends on two things you already know: whether your camera is **mono or one-shot-color**, and how **light-polluted** your sky is. Decide from those, not from a wishlist.

1. Mono vs OSC changes everything

  • Mono camera: you need filters to make color — LRGB for broadband targets, narrowband

(Ha/OIII/SII) for emission nebulae. This is the main reason to go mono.

  • OSC camera: color is built in. You don't need LRGB; you may add a dual/multi-band narrowband

filter to cut light pollution and boost nebulae in one shot.

2. Match to your sky

  • Dark sky, broadband targets (galaxies): LRGB (mono) or no filter (OSC).
  • Light-polluted sky, emission nebulae: narrowband is transformative — it rejects most light

pollution and isolates the gas. For OSC, a dual-band (Ha+OIII) filter is the high-impact buy.

3. Specs that matter

  • Bandwidth (narrower rejects more light pollution/moon but passes less light, so it needs longer

exposures — most punishing on a slow scope; this is separate from the f-ratio effect below).

  • Size/format (mounted vs unmounted; fits your filter wheel/drawer and avoids vignetting).
  • f-ratio rating — fast scopes can shift narrowband band centers; check the filter is rated for

your f-ratio.

4. Sensible order to buy

  1. OSC in light pollution → a dual-band filter first.
  2. Mono → Ha first (huge impact, moon-tolerant), then OIII/SII, then LRGB.

Which set, and the trade-offs between them, is its own comparison — see

broadband vs narrowband and

narrowband filter sets.

5. Budget tiers (confirm current models)

  • Entry (OSC): one dual-band filter.
  • Mid (mono): Ha + OIII + SII set, or LRGB + Ha.

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What filters do: filters in astrophotography.