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"
$ 414.00
Omegon
Filters OIII filter 1.25''
$ 89.00
Omegon
Filters OIII Filter 2"
$ 119.00
Optolong
Filters L-Ultimate 1,25"
$ 269.00
Omegon
Filters Pro 2'' H-alpha filter
$ 209.00
Omegon
Filters Pro 2'' SII CCD filter
$ 189.00
Omegon
Filters Pro 2'' OIII CCD filter
$ 179.00
Optolong
Filters SHO Filter Kit 1,25"
$ 550.00
Optolong
Filters SII Filter 2"
RRP:
$ 248.00
Our price:
$ 238.00
Omegon
Filters Pro 1.25'' H-Beta filter
$ 99.00
Astronomik
Filters 1.25" OIII filter
$ 103.00
Baader
Filters H-alpha/OIII/SII CMOS f/2 Ultra-Highspeed 2"
$ 1,140.00
Baader
Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 2"
$ 1,090.00
Omegon
Filters Pro 1.25'' OIII CCD filter
$ 129.00
Omegon
Filters Pro 1.25'' H-alpha filter
$ 149.00
Astronomik
Filters H-alpha 6nm CCD Clip Canon EOS R XL
$ 550.00
Baader
Filters H-alpha/OIII/SII CMOS f/2 Highspeed 1.25"
$ 434.00
Optolong
SII Filters 1.25"
$ 150.00
Omegon
Filters Pro 1.25'' SII CCD filter
$ 129.00
Astronomik
Filters H-alpha 12nm CCD Clip-Filter Sony alpha
$ 352.00
Optolong
Filters SHO Filter Kit 3nm 2"
$ 1,330.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 2"
$ 690.00
Optolong
Filters SHO Filter Kit 2"
$ 750.00
Astronomik
Filters SII 6nm CCD MaxFR 2"
$ 710.00
Astronomik
Filters OIII 6nm CCD MaxFR 2"
$ 710.00
IDAS
Filters OIII 6.0nm 2
$ 414.00
Baader
Filters H-alpha 20nm 2"
$ 171.00
Chroma
Filters H-Alpha 1,25", 3nm
RRP:
$ 1,030.00
Our price:
$ 670.00
Baader
Filters OIII Super-G 2"
$ 171.00
Baader
Filters OIII CMOS Narrowband 50.4mm
$ 285.00
Astronomik
Filters H-beta 2"
$ 207.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 36mm
$ 482.00
Baader
Filters H-alpha CMOS f/3 Ultra-Highspeed 50.4mm
$ 431.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 207.00
Baader
Filters H-alpha/OIII/SII CMOS Narrowband 31mm
$ 425.00
