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)
![DayStar QUARK Magnesium I (b2) Line](/Produktbilder/normal/59411_1/DayStar-QUARK-Magnesium-I-b2-Line.jpg)
DayStar
QUARK Magnesium I (b2) Line
$ 2,240.00
![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
$ 3,430.00
![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
$ 2,900.00
![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
$ 3,000.00
![Lunt Solar Systems Ca-K module with 2", 6mm blocking filter in extension tube for 2" focuser](/Produktbilder/normal/15917_1/Lunt-Solar-Systems-Ca-K-module-with-2-6mm-blocking-filter-in-extension-tube-for-2-focuser.jpg)
Lunt Solar Systems
Ca-K module with 2", 6mm blocking filter in extension tube for 2" focuser
$ 2,040.00
![DayStar QUARK H-alpha filter,chromosphere](/Produktbilder/normal/44774_1/DayStar-QUARK-H-alpha-filter-chromosphere.jpg)
DayStar
QUARK H-alpha filter,chromosphere
Our price:
RRP:
$ 1,920.00
$ 1,610.00
![DayStar QUARK H-alpha filter, prominences](/Produktbilder/normal/44774_1/DayStar-QUARK-H-alpha-filter-prominences.jpg)
DayStar
QUARK H-alpha filter, prominences
Our price:
RRP:
$ 1,920.00
$ 1,500.00
![DayStar QUARK H-Alpha solar filter for Canon DSLR, prominence model](/Produktbilder/normal/52375_1/DayStar-QUARK-H-Alpha-solar-filter-for-Canon-DSLR-prominence-model.jpg)
DayStar
QUARK H-Alpha solar filter for Canon DSLR, prominence model
Our price:
RRP:
$ 2,240.00
$ 1,600.00
![DayStar QUARK H-Alpha solar filter for Nikon DSLR, chromosphere model](/Produktbilder/normal/52375_1/DayStar-QUARK-H-Alpha-solar-filter-for-Nikon-DSLR-chromosphere-model.jpg)
DayStar
QUARK H-Alpha solar filter for Nikon DSLR, chromosphere model
$ 2,240.00
![DayStar QUARK H-Alpha solar filter for Canon DSLR, chromosphere model](/Produktbilder/normal/52375_1/DayStar-QUARK-H-Alpha-solar-filter-for-Canon-DSLR-chromosphere-model.jpg)
DayStar
QUARK H-Alpha solar filter for Canon DSLR, chromosphere model
Our price:
RRP:
$ 2,240.00
$ 1,600.00
![DayStar Combo QUARK H-Alpha solar filter, for prominences](/Produktbilder/normal/48678_1/DayStar-Combo-QUARK-H-Alpha-solar-filter-for-prominences.jpg)
DayStar
Combo QUARK H-Alpha solar filter, for prominences
Our price:
RRP:
$ 1,920.00
$ 1,500.00
![DayStar QUARK Sodium D-Line](/Produktbilder/normal/51926_1/DayStar-QUARK-Sodium-D-Line.jpg)
DayStar
QUARK Sodium D-Line
Our price:
RRP:
$ 1,920.00
$ 1,800.00
![DayStar Combo QUARK H-Alpha solar filter, for chromosphere](/Produktbilder/normal/48678_1/DayStar-Combo-QUARK-H-Alpha-solar-filter-for-chromosphere.jpg)
DayStar
Combo QUARK H-Alpha solar filter, for chromosphere
Our price:
RRP:
$ 1,920.00
$ 1,500.00
![Baader Solar Filter SunDancer II TZ-3S H-alpha 2"/1.25"](/Produktbilder/normal/71929_1/Baader-Solar-Filter-SunDancer-II-TZ-3S-H-alpha-2-1-25-.jpg)
Baader
Solar Filter SunDancer II TZ-3S H-alpha 2"/1.25"
$ 3,800.00
![DayStar QUARK H-alpha filter Gemini](/Produktbilder/normal/62635_1/DayStar-QUARK-H-alpha-filter-Gemini.jpg)
DayStar
QUARK H-alpha filter Gemini
$ 3,740.00
![DayStar QUARK Calcium-H-Line](/Produktbilder/normal/49965_1/DayStar-QUARK-Calcium-H-Line.jpg)