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"
$ 416.00
Optolong
Filters SHO Filter Kit 7nm 2"
$ 800.00
Omegon
Filters OIII filter 1.25''
$ 79.00
DayStar
QUARK H-alpha filter,chromosphere
$ 1,850.00
Omegon
Filters OIII Filter 2"
$ 99.00
Optolong
Filters L-Synergy 2"
$ 382.00
Optolong
Filters SHO 3nm 2"
$ 1,160.00
Optolong
Filters SHO Filter Kit 1,25"
$ 580.00
Omegon
Filters Pro 2'' H-Beta filter
$ 119.00
Optolong
Filters L-Ultimate 1,25"
$ 312.00
Astronomik
Filters 1.25" OIII filter
$ 115.00
Omegon
Filters Pro Veil H-Alpha OIII 7nm 2''
$ 239.00
Optolong
Filters L2 Dual-Combo Set 2"
$ 690.00
DayStar
Filters 0.5Å H-alpha Quantum PE filter
$ 27,300.00
DayStar
Combo QUARK H-Alpha solar filter, for chromosphere
$ 1,850.00
Lunt Solar Systems
Filters H-alpha double-stack for LS60FHa
RRP:
$ 3,470.00
Our price:
$ 2,760.00
Askar
Filters Color Magic D2 OIII/SII Duo 2"
$ 439.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Sony alpha 7
$ 570.00
Baader
Filters H-alpha/OIII/SII CMOS f/2 Ultra-Highspeed 36mm
$ 1,090.00
Astronomik
Filters 2" OIII filter
$ 231.00
Baader
Filters H-alpha/OIII/SII CMOS f/2 Ultra-Highspeed 31mm
$ 910.00
Lunt Solar Systems
Filters LS50C double-stack filter
RRP:
$ 1,960.00
Our price:
$ 1,690.00
Omegon
Filters Pro 1.25'' SII CCD filter
$ 129.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 2"
$ 770.00
Optolong
Filters SHO 3nm 36mm
$ 1,000.00
Antlia
Filters H-Alpha Pro 3nm 36mm
$ 590.00
Baader
Filters OIII CMOS Narrowband 1.25"
$ 158.00
Astronomik
Filters HSO 6nm 36mm
$ 870.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 231.00
DayStar
QUARK H-alpha filter, prominences
$ 1,850.00
Baader
Filters H-alpha CMOS Narrowband 1.25"
$ 161.00
Optolong
Filters SII 6.5nm 2"
$ 254.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 36mm
$ 540.00
DayStar
QUARK Magnesium I (b2) Line
$ 2,080.00
QHY
Filters LRGB + 3nm SHO miniCam8
$ 580.00
