Filters < Astronomy Type of build line filter

Line filters selectively allow only light from a specific spectral line to pass through. OIII, SII and H-alpha filters are especially popular.

The Roman numerals III and II indicate the degree of ionisation of the chemical element that produces the spectral line. So OIII (pronounce oh three) stands for doubly ionised oxygen, and SII for singly ionised sulphur. OI and SI indicate the electrically neutral atoms.

Line filters are ideal for the visual observation and photography of emission nebulae, supernova remnants and planetary nebulae, since these objects produce defined spectral lines. Star clusters and galaxies on the other hand have a continuous spectrum. For these, filters that generally suppress the sky’s brightness (CLS or UHC filters) are more suitable.

Example of an emission line spectrum (source: Wikipedia)

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Optolong

Filters L-Ultimate 2"

$ 414.00

Product can be shipped as of 01.02.2025

Filters

Type of build: line filter

Optolong

Filters L-Ultimate 2"

$ 414.00

Omegon

Filters OIII filter 1.25''

$ 89.00

Omegon

Filters OIII Filter 2"

$ 119.00

Optolong

Filters L-Ultimate 1,25"

$ 269.00

Omegon

Filters Pro 2'' H-alpha filter

$ 209.00

Omegon

Filters Pro 2'' SII CCD filter

$ 189.00

Omegon

Filters Pro 2'' OIII CCD filter

$ 179.00

Optolong

Filters SHO Filter Kit 1,25"

$ 550.00

Optolong

Filters SII Filter 2"

RRP: $ 248.00

Our price:

Omegon

Filters Pro 1.25'' H-Beta filter

$ 99.00

Astronomik

Filters 1.25" OIII filter

$ 103.00

Coronado

Filters Double Stacking Etalon Solarmax II PST 40mm

$ 1,550.00

DayStar

Filters 0.5Å H-alpha Quantum PE filter

$ 27,100.00

Lunt Solar Systems

Solar Filters Ca-K module for LS130MT/B3400

$ 3,630.00

Baader

Filters H-alpha/OIII/SII CMOS f/2 Ultra-Highspeed 2"

$ 1,140.00

Baader

Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 2"

$ 1,090.00

Omegon

Filters Pro 1.25'' OIII CCD filter

$ 129.00

Omegon

Filters Pro 1.25'' H-alpha filter

$ 149.00

Astronomik

Filters H-alpha 6nm CCD Clip Canon EOS R XL

$ 550.00

Baader

Filters H-alpha/OIII/SII CMOS f/2 Highspeed 1.25"

$ 434.00

Optolong

SII Filters 1.25"

$ 150.00

Omegon

Filters Pro 1.25'' SII CCD filter

$ 129.00

Astronomik

Filters H-alpha 12nm CCD Clip-Filter Sony alpha

$ 352.00

Baader

Filters K-LINE filter gestackt, 1 ¼ " (with 3,8 astro+solarly 200x290mm photo film)

$ 296.00

Optolong

Filters SHO Filter Kit 3nm 2"

$ 1,330.00

Baader

Filters H-alpha/OIII/SII CMOS Narrowband 2"