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)
Optolong
Filters L-Ultimate 2"
$ 415.00
Omegon
Filters OIII Filter 2"
$ 99.00
Omegon
Filters OIII filter 1.25''
$ 79.00
DayStar
QUARK H-alpha filter,chromosphere
$ 1,840.00
Optolong
Filters SHO Filter Kit 7nm 2"
$ 970.00
Optolong
Filters L-Ultimate 1,25"
$ 311.00
Omegon
Filters 7nm H-alpha 1.25 pro filter
$ 199.00
Optolong
Filters L2 Dual-Combo Set 2"
$ 670.00
Optolong
Filters SHO 3nm 36mm
$ 990.00
Astronomik
Filters 1.25" OIII filter
$ 115.00
Omegon
Filters Pro Veil H-Alpha OIII 7nm 2''
$ 199.00
Optolong
Filters L-Synergy 2"
$ 381.00
Optolong
Filters SHO 3nm 2"
$ 1,160.00
DayStar
Filters 0.5Å H-alpha Quantum PE filter
$ 27,200.00
ZWO
Filters Narrowband Filter Set H-alpha, SII, OIII 2"
$ 1,160.00
ZWO
Filters Filter set H-alpha, SII, OIII 36mm unmounted
$ 810.00
Omegon
Filters Pro 2'' SII CCD filter
$ 179.00
Baader
Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 50x50mm
$ 1,400.00
Askar
Filters Color Magic D2 OIII/SII Duo 2"
$ 450.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Sony alpha 7
$ 570.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 230.00
Optolong
Filters SII 6.5nm 2"
$ 253.00
Astronomik
Filters HSO 6nm 2"
$ 1,340.00
Omegon
Filters Pro 2'' H-Beta filter
$ 129.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Nikon XL
$ 570.00
Lunt Solar Systems
Filters LS50C double-stack filter
RRP:
$ 1,970.00
Our price:
$ 1,380.00
Omegon
Filters Pro 1.25'' H-Beta filter
$ 99.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 2"
$ 770.00
Baader
Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 1.25"
$ 840.00
Baader
Filters H-alpha 20nm 2"
$ 191.00
Optolong
Filters SHO Filter Kit 1,25"
$ 640.00
Baader
Filters OIII CMOS Narrowband 1.25"
$ 158.00
Astronomik
Filters HSO 6nm 36mm
$ 870.00
Coronado
Filters Double Stacking Etalon Solarmax II PST 40mm
$ 1,380.00
DayStar
QUARK H-alpha filter, prominences
$ 1,840.00
