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)](/CMS/images/text/glossary/Emissionslinien_Wikipedia.png)
![Coronado Filters SolarMax III H-Alpha-Etalon 90mm BF30](/Produktbilder/normal/59473_1/Coronado-Filters-SolarMax-III-H-Alpha-Etalon-90mm-BF30.jpg)
Coronado
Filters SolarMax III H-Alpha-Etalon 90mm BF30
$ 7,200.00
![Coronado Filters SolarMax III H-Alpha-Etalon 60mm BF10](/Produktbilder/normal/59478_2/Coronado-Filters-SolarMax-III-H-Alpha-Etalon-60mm-BF10.jpg)
Coronado
Filters SolarMax III H-Alpha-Etalon 60mm BF10
$ 2,470.00
![Coronado Filters SolarMax III H-Alpha-Etalon 60mm BF30](/Produktbilder/normal/59478_1/Coronado-Filters-SolarMax-III-H-Alpha-Etalon-60mm-BF30.jpg)
Coronado
Filters SolarMax III H-Alpha-Etalon 60mm BF30
$ 4,090.00
![Coronado Filters SolarMax III H-Alpha-Etalon 60mm BF15](/Produktbilder/normal/59478_2/Coronado-Filters-SolarMax-III-H-Alpha-Etalon-60mm-BF15.jpg)
Coronado
Filters SolarMax III H-Alpha-Etalon 60mm BF15
$ 2,690.00
![DayStar QUARK Magnesium I (b2) Line](/Produktbilder/normal/59411_1/DayStar-QUARK-Magnesium-I-b2-Line.jpg)
DayStar
QUARK Magnesium I (b2) Line
$ 2,260.00
![Lunt Solar Systems Filters H-alpha LS50FHa/B1800d1](/Produktbilder/normal/12689_2/Lunt-Solar-Systems-Filters-H-alpha-LS50FHa-B1800d1.jpg)
Lunt Solar Systems
Filters H-alpha LS50FHa/B1800d1
$ 3,990.00
![Lunt Solar Systems Sonnenfilter Ca-K-Modul für LS130MT](/Produktbilder/normal/67743_1/Lunt-Solar-Systems-Sonnenfilter-Ca-K-Modul-fuer-LS130MT.jpg)
Lunt Solar Systems
Sonnenfilter Ca-K-Modul für LS130MT
$ 2,920.00
![Coronado Filters SolarMax III H-Alpha-Etalon 90mm BF15](/Produktbilder/normal/59470_1/Coronado-Filters-SolarMax-III-H-Alpha-Etalon-90mm-BF15.jpg)
Coronado
Filters SolarMax III H-Alpha-Etalon 90mm BF15
$ 5,200.00
![Lunt Solar Systems Sonnenfilter Ca-K-Modul für LS130MT/B3400](/Produktbilder/normal/69451_1/Lunt-Solar-Systems-Sonnenfilter-Ca-K-Modul-fuer-LS130MT-B3400.jpg)
Lunt Solar Systems
Sonnenfilter Ca-K-Modul für LS130MT/B3400
$ 3,450.00
![Baader Filters K-LINE filter gestackt, 1 ¼ " (with 3,8 astro+solarly 200x290mm photo film)](/Produktbilder/normal/10887_1/Baader-Filters-K-LINE-filter-gestackt-1-f-with-3-8-astro-solarly-200x290mm-photo-film-.jpg)
Baader
Filters K-LINE filter gestackt, 1 ¼ " (with 3,8 astro+solarly 200x290mm photo film)
$ 308.00
![Lunt Solar Systems Filters 50mm Ha Etalon filter](/Produktbilder/normal/15907_2/Lunt-Solar-Systems-Filters-50mm-Ha-Etalon-filter.jpg)
Lunt Solar Systems
Filters 50mm Ha Etalon filter
$ 2,110.00
![Lunt Solar Systems Ca-K Module with 18mm blocking filter in extension tube for 2" focuser](/Produktbilder/normal/15911_1/Lunt-Solar-Systems-Ca-K-Module-with-18mm-blocking-filter-in-extension-tube-for-2-focuser.jpg)
Lunt Solar Systems
Ca-K Module with 18mm blocking filter in extension tube for 2" focuser
$ 3,020.00
![Lunt Solar Systems Filters LS 50F Ha H-Alpha filter set for 1200mm focal length](/Produktbilder/normal/12688_1/Lunt-Solar-Systems-Filters-LS-50F-Ha-H-Alpha-filter-set-for-1200mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 50F Ha H-Alpha filter set for 1200mm focal length
$ 3,240.00
![Lunt Solar Systems Filters H-alpha LS50FHa/B600d1](/Produktbilder/normal/12687_1/Lunt-Solar-Systems-Filters-H-alpha-LS50FHa-B600d1.jpg)
Lunt Solar Systems
Filters H-alpha LS50FHa/B600d1
$ 2,700.00
![Lunt Solar Systems Filters LS 100F Ha H-Alpha filter set for 600mm focal length](/Produktbilder/normal/12697_1/Lunt-Solar-Systems-Filters-LS-100F-Ha-H-Alpha-filter-set-for-600mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 100F Ha H-Alpha filter set for 600mm focal length
$ 12,200.00
![Lunt Solar Systems Filters H-alpha LS50FHa/B600d2](/Produktbilder/normal/15921_3/Lunt-Solar-Systems-Filters-H-alpha-LS50FHa-B600d2.jpg)
Lunt Solar Systems
Filters H-alpha LS50FHa/B600d2
$ 2,700.00
![Lunt Solar Systems Filters 50mm Ha Etalon filter with B1800 for 2" focuser](/Produktbilder/normal/15922_1/Lunt-Solar-Systems-Filters-50mm-Ha-Etalon-filter-with-B1800-for-2-focuser.jpg)
Lunt Solar Systems
Filters 50mm Ha Etalon filter with B1800 for 2" focuser
$ 3,990.00
![Lunt Solar Systems Filters 50mm Ha Etalon filter with B1200 for 2" focuser](/Produktbilder/normal/15923_1/Lunt-Solar-Systems-Filters-50mm-Ha-Etalon-filter-with-B1200-for-2-focuser.jpg)
Lunt Solar Systems
Filters 50mm Ha Etalon filter with B1200 for 2" focuser
$ 3,240.00
![Lunt Solar Systems Filters LS 100F Ha H-Alpha filter set for 1800mm focal length](/Produktbilder/normal/12699_1/Lunt-Solar-Systems-Filters-LS-100F-Ha-H-Alpha-filter-set-for-1800mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 100F Ha H-Alpha filter set for 1800mm focal length
$ 13,500.00
![Lunt Solar Systems Filters LS 100F Ha H-Alpha filter set for 3400mm focal length](/Produktbilder/normal/12700_1/Lunt-Solar-Systems-Filters-LS-100F-Ha-H-Alpha-filter-set-for-3400mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 100F Ha H-Alpha filter set for 3400mm focal length
$ 15,100.00
![Lunt Solar Systems Filters LS 50F Ha H-Alpha filter set for 3400mm focal length](/Produktbilder/normal/12690_1/Lunt-Solar-Systems-Filters-LS-50F-Ha-H-Alpha-filter-set-for-3400mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 50F Ha H-Alpha filter set for 3400mm focal length
$ 5,800.00
![Lunt Solar Systems Filters H-alpha double-stack solar filter LS100FHa](/Produktbilder/normal/15931_1/Lunt-Solar-Systems-Filters-H-alpha-double-stack-solar-filter-LS100FHa.jpg)
Lunt Solar Systems
Filters H-alpha double-stack solar filter LS100FHa
$ 11,500.00
![Lunt Solar Systems Filters 100mm Ha Etalon filter with B1200 for 2" focuser](/Produktbilder/normal/15932_1/Lunt-Solar-Systems-Filters-100mm-Ha-Etalon-filter-with-B1200-for-2-focuser.jpg)
Lunt Solar Systems
Filters 100mm Ha Etalon filter with B1200 for 2" focuser
$ 12,900.00
![Lunt Solar Systems Filters 100mm Ha Etalon filter with B1800 for 2" focuser](/Produktbilder/normal/15951_1/Lunt-Solar-Systems-Filters-100mm-Ha-Etalon-filter-with-B1800-for-2-focuser.jpg)
Lunt Solar Systems
Filters 100mm Ha Etalon filter with B1800 for 2" focuser
$ 13,500.00
![Lunt Solar Systems Filters LS 100F Ha H-Alpha filter set for 1200mm focal length](/Produktbilder/normal/12698_1/Lunt-Solar-Systems-Filters-LS-100F-Ha-H-Alpha-filter-set-for-1200mm-focal-length.jpg)
Lunt Solar Systems
Filters LS 100F Ha H-Alpha filter set for 1200mm focal length
$ 12,900.00
![Lunt Solar Systems Filters LS60FHa B3400 2" etalon filter system](/Produktbilder/normal/33254_1/Lunt-Solar-Systems-Filters-LS60FHa-B3400-2-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B3400 2" etalon filter system
$ 7,100.00
![Lunt Solar Systems Filters 100mm Ha Etalon filter with B600 for 2" focuser](/Produktbilder/normal/15950_1/Lunt-Solar-Systems-Filters-100mm-Ha-Etalon-filter-with-B600-for-2-focuser.jpg)
Lunt Solar Systems
Filters 100mm Ha Etalon filter with B600 for 2" focuser
$ 12,200.00
![Lunt Solar Systems Filters H-Alpha Doublestack LS40F](/Produktbilder/normal/83312_1/Lunt-Solar-Systems-Filters-H-Alpha-Doublestack-LS40F.jpg)
Lunt Solar Systems
Filters H-Alpha Doublestack LS40F
$ 1,080.00
![Lunt Solar Systems Filters LS60FHa B1800 1.25" etalon filter system](/Produktbilder/normal/33253_1/Lunt-Solar-Systems-Filters-LS60FHa-B1800-1-25-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B1800 1.25" etalon filter system
$ 5,400.00
![Lunt Solar Systems Filters LS60FHa B1200 1.25" etalon filter system](/Produktbilder/normal/33251_1/Lunt-Solar-Systems-Filters-LS60FHa-B1200-1-25-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B1200 1.25" etalon filter system
$ 4,640.00
![Lunt Solar Systems Filters LS60FHa B600 1.25" etalon filter system](/Produktbilder/normal/33249_1/Lunt-Solar-Systems-Filters-LS60FHa-B600-1-25-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B600 1.25" etalon filter system
$ 4,100.00
![Lunt Solar Systems Filters LS60FHa B1200 2" etalon filter system](/Produktbilder/normal/33250_1/Lunt-Solar-Systems-Filters-LS60FHa-B1200-2-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B1200 2" etalon filter system
$ 4,640.00
![Lunt Solar Systems Filters LS60FHa B1800 2" etalon filter system](/Produktbilder/normal/33252_1/Lunt-Solar-Systems-Filters-LS60FHa-B1800-2-etalon-filter-system.jpg)
Lunt Solar Systems
Filters LS60FHa B1800 2" etalon filter system
$ 5,400.00
![Lunt Solar Systems Filters Ca-K module with 12mm blocking filter in extension tube for 2" focuser](/Produktbilder/normal/15911_1/Lunt-Solar-Systems-Filters-Ca-K-module-with-12mm-blocking-filter-in-extension-tube-for-2-focuser.jpg)
Lunt Solar Systems
Filters Ca-K module with 12mm blocking filter in extension tube for 2" focuser
$ 2,590.00
![Lunt Solar Systems Filters Ca-K module with 12mm blocking filter in star diagonal for 2" focuser](/Produktbilder/normal/15952_1/Lunt-Solar-Systems-Filters-Ca-K-module-with-12mm-blocking-filter-in-star-diagonal-for-2-focuser.jpg)
Lunt Solar Systems
Filters Ca-K module with 12mm blocking filter in star diagonal for 2" focuser
$ 2,590.00
![Lunt Solar Systems Filters Ca-K module with 18mm blocking filter in star diagonal for 2" focuser](/Produktbilder/normal/15946_1/Lunt-Solar-Systems-Filters-Ca-K-module-with-18mm-blocking-filter-in-star-diagonal-for-2-focuser.jpg)