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)
Omegon
Filters OIII filter 1.25''
$ 89.00
Omegon
Filters OIII Filter 2"
$ 119.00
Omegon
Filters Pro 2'' SII CCD filter
$ 189.00
Omegon
Filters Pro 1.25'' H-Beta filter
$ 99.00
Omegon
Filters Pro 2'' OIII CCD filter
$ 179.00
Omegon
Filters Pro 1.25'' OIII CCD filter
$ 129.00
Omegon
Filters Pro SII 7nm Filter 1.25"
RRP:
$ 179.00
Our price:
$ 149.00
Omegon
Filters Pro 1.25'' SII CCD filter
$ 129.00
Optolong
Filters SII Filter 2"
RRP:
$ 249.00
Our price:
$ 238.00
Omegon
Filters Pro 1.25'' H-alpha filter
$ 149.00
Optolong
Filters SHO Filter Kit 3nm 2"
$ 1,340.00
Optolong
Filters L-Ultimate 1,25"
$ 270.00
Omegon
Filters 7nm H-alpha 1.25 pro filter
$ 199.00
Optolong
Filters L-Ultimate 2"
$ 415.00
Explore Scientific
Filters 2" H-Beta filter
RRP:
$ 126.00
Our price:
$ 78.00
Astronomik
Filters 2" OIII filter
$ 207.00
Astronomik
Filters 1.25" OIII filter
$ 103.00
Explore Scientific
Filters Filter UHC 2"
$ 114.00
STC
Filters Duo-NB Clip Canon (Full Frame)
$ 488.00
Omegon
Filters Pro OIII 7nm Filter 1,25"
RRP:
$ 179.00
Our price:
$ 149.00
Explore Scientific
Filters SII 6.5nm 2"
RRP:
$ 238.00
Our price:
$ 120.00
Explore Scientific
Filters 1.25" OIII filter
$ 76.00
Explore Scientific
Filters OIII 6.5nm 1.25"
RRP:
$ 166.00
Our price:
$ 84.00
Astronomik
Filters H-alpha 12nm CCD Clip-Filter Sony alpha
$ 353.00
Optolong
SII Filters 1.25"
$ 150.00
Explore Scientific
Filters 2" OIII filter
$ 135.00
Omegon
Filters Pro 2'' H-alpha filter
$ 209.00
Optolong
Filters SHO Filter Kit 1,25"
$ 550.00
Astronomik
Filters H-alpha 12nm CCD Clip Canon EOS APS-C
$ 207.00
Baader
Filters OIII CMOS Narrowband 50x50mm
$ 297.00
Optolong
Filters SHO Filter Kit 2"
$ 750.00
Baader
Filters H-Beta CMOS Narrowband 2"
$ 307.00
ZWO
Filters Filter CH4 1.25"
RRP:
$ 155.00
Our price:
$ 152.00
Explore Scientific
Filters H-alpha 7nm 2"
$ 238.00
Optolong
Filters SII 3nm 2"
$ 940.00
