Air This is not a filter as such but is the position where the empty (i.e. no filter) position in each of the 3 interlocking filter wheels line up. The light collected will only be limited to the range of frequencies the CCD can see.
Bessell B Wavelength Width (Å): 890Wavelength Center (Å): 4361UCD electromagnetic spectrum identifier: em.opt.B
Bessell I Wavelength Center (Å): 7980UCD electromagnetic spectrum identifier: em.opt.IWavelength Width (Å): 1540RTI filter code: BI
Bessell R Wavelength Center (Å): 6407UCD electromagnetic spectrum identifier: em.opt.RWavelength Width (Å): 1580RTI filter code: CR
Bessell U Wavelength Center (Å): 3500UCD electromagnetic spectrum identifier: em.opt.UWavelength Width (Å): 500RTI filter code: BU
Bessell V Wavelength Center (Å): 5448UCD electromagnetic spectrum identifier: em.opt.VWavelength Width (Å): 840RTI filter code: CV
D51 Wavelength Center (Å): 150UCD electromagnetic spectrum identifier: em.opt.VWavelength Width (Å): 5150RTI filter code: D51
H alpha Wavelength Center (Å): 6563UCD electromagnetic spectrum identifier: em.line.HalphaWavelength Width (Å): 300RTI filter code: CA
H beta Wavelength Center (Å): 4860UCD electromagnetic spectrum identifier: em.line.HbetaWavelength Width (Å): 300RTI filter code: HB
ND2 Reflective neutral density filter. This filter is always used in conjunction with another filter and reduces the intensity of light that hits the CCD by a factor of 100.