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"
$ 424.00
Omegon
Filters OIII filter 1.25''
$ 79.00
Omegon
Filters OIII Filter 2"
$ 99.00
Optolong
Filters L-Synergy 2"
$ 389.00
Optolong
Filters L-Ultimate 1,25"
$ 318.00
Optolong
Filters SHO Filter Kit 7nm 2"
$ 820.00
Omegon
Filters Pro Veil H-Alpha OIII 7nm 2''
$ 239.00
Omegon
Filters Pro 2'' H-Beta filter
$ 119.00
Astronomik
Filters 1.25" OIII filter
$ 117.00
Askar
Filters Color Magic D2 OIII/SII Duo 2"
$ 448.00
Askar
Filters Color Magic D1 OIII/H-Alpha Duo 2"
$ 448.00
Optolong
Filters SHO 6,5-7nm 36mm
$ 590.00
Optolong
Filters SHO 3nm 2"
$ 1,180.00
Omegon
Filters Pro OIII 7nm Filter 1,25"
$ 189.00
Omegon
Filters 7nm H-alpha 1.25 pro filter
$ 189.00
Omegon
Filters Pro Veil H-Alpha 7nm 2''
$ 239.00
Baader
Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 36mm
$ 1,170.00
Optolong
Filters SII 6.5nm 2"
$ 259.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 2"
$ 840.00
Astronomik
Filters 2" OIII filter
$ 235.00
ZWO
Filters Narrowband Filter Set H-alpha, SII, OIII 2"
$ 1,150.00
Omegon
Filters Pro 1.25'' H-Beta filter
$ 99.00
Chroma
Filters OIII 36mm unmounted, 3nm
RRP:
$ 1,410.00
Our price:
$ 1,230.00
ZWO
Filters Filter set H-alpha, SII, OIII 36mm unmounted
$ 770.00
Optolong
Filters SHO 3nm 36mm
$ 1,020.00
Astronomik
Filters H-alpha 6nm CCD MaxFR Clip Sony alpha 7
$ 830.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Sony alpha 7
$ 580.00
ZWO
Filters 1.25" filter set: H-alpha, SII, OIII
$ 590.00
Astronomik
Filters HSO 6nm 36mm
$ 890.00
Baader
Filters H-alpha CMOS Narrowband 1.25"
$ 176.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 235.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 36mm
$ 590.00
Baader
Filters H-alpha CMOS Ultra-Narrowband 50.4mm
$ 530.00
Astronomik
Filters H-alpha 6nm CCD filter, 50x50mm, unmounted
$ 590.00
Astronomik
Filters H-alpha 6nm CCD EOS XL clip-filter
$ 590.00
