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''
$ 79.00
Omegon
Filters OIII Filter 2"
$ 99.00
Optolong
Filters SHO Filter Kit 7nm 2"
$ 970.00
Optolong
Filters SII 6.5nm 2"
$ 253.00
Astronomik
Filters 1.25" OIII filter
$ 114.00
Optolong
Filters L-Ultimate 1,25"
$ 310.00
Omegon
Filters Pro 1.25'' H-Beta filter
$ 99.00
Omegon
Filters 7nm H-alpha 1.25 pro filter
$ 199.00
Optolong
Filters SHO 3nm 2"
$ 1,160.00
Omegon
Filters Pro 2'' SII CCD filter
$ 179.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 230.00
Astronomik
Filters HSO 6nm 36mm
$ 870.00
ZWO
Filters Narrowband Filter Set H-alpha, SII, OIII 2"
$ 1,160.00
Omegon
Filters Pro 2'' H-Beta filter
$ 129.00
Omegon
Filters Pro OIII 7nm Filter 1,25"
$ 199.00
Omegon
Filters Pro SII 7nm Filter 1.25"
$ 199.00
Astronomik
Filters H-alpha 12nm CCD Clip-Filter Sony alpha
$ 391.00
ZWO
Filters Filter set H-alpha, SII, OIII 36mm unmounted
$ 810.00
Baader
Filters H-alpha/OIII/SII CMOS Ultra-Narrowband 1.25"
$ 830.00
Astronomik
Filters 2" OIII filter
$ 230.00
Optolong
Filters SHO Filter Kit 1,25"
RRP:
$ 640.00
Our price:
$ 510.00
Optolong
Filters H-alpha 3nm 2"
$ 448.00
Baader
Filters H-alpha CMOS Narrowband 1.25"
$ 161.00
Baader
Filters Ultra-Narrowband SII CMOS 50.4mm
$ 448.00
Baader
Filters OIII CMOS Narrowband 1.25"
$ 157.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip EOS R XL
$ 570.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Sony alpha 7
$ 570.00
Astronomik
Filters H-alpha 12nm MaxFR XT Clip Nikon XL
$ 570.00
Astronomik
Filters H-alpha 6nm CCD MaxFR 2"
$ 790.00
Astronomik
Filters H-alpha 2" 6nm CCD filter
$ 570.00
Astronomik
Filters OIII 6nm CCD 2"
$ 570.00
Baader
Filters OIII Super-G 1.25"
$ 103.00
Astronomik
Filters H-alpha 12nm CCD MaxFR Clip Sony alpha 7
$ 520.00
Baader
Filters H-alpha 20nm 1.25"
$ 109.00
