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Narrow band filters

At present, we have 31 narrow band filters, mostly of 50Å bandwidth, comprising a set of emission line filters and a set of redshifted H_alpha redshifted filters. Only one set exists and therefore the filters are shared between the INT and JKT. These filters were specified for a focal ratio of 4.5 which explains the difference in wavelength between the actual peak wavelength and the required peak wavelength. The original specification for the emission line filters is given below:

Unless otherwise specified the effects of an f/4.5 converging beam of light has been taken into account and the central wavelength duly reddened. A correction of +2 Angstroms has also been made to correct the central wavelength for operation at +10 degrees Celsius on the assumption that the filters will be made, tested and specified at +20 degrees Celsius.

In all cases the thickness of the filter including blocking filters should not exceed 9mm and should be the same for all filters wherever possible. The effective refractive index should be near 2.1. Blocking in all cases should be 3000-12000 Angstroms and the tolerance on the central wavelength should be better than 3 Angstroms. The tolerance on the dimensions of each filter should be smaller than 0.5mm. Filters should be free from pinholes greater than 0.03mm diameter in the central 25mm diameter circle and free from pinholes greater than 0.1mm diameter elsewhere.

Here the transmission curves for the filters:

1. The emission line set (except H_alpha)

[OII] 3727 [SII] 4075 HeII 4691 H beta [OIII] 5007 He II 5881 [OI] 6306 [OI] 6306 large scan H alpha [NII] 6590 [SII] 6730 [OII] 7331 [SIII] 9069 [SIII] 9539 HeII 10837

2. The old redshifted H_alpha filters:

H_alpha 6556 H_alpha 6563 H_alpha 6607 H_alpha 6652 H_alpha 6700 H_alpha 6742 H_alpha 6789 H_alpha 6835 H_alpha 6877 H_alpha 6925 H_alpha 6970

3. The new redshifted H_alpha filters:

H_alpha 6565/45 H_alpha 6565/60 H_alpha 6595/45 H_alpha 6625/45 H_alpha 6655/45 H_alpha 6685/45 H_alpha 6715/45

and here we present the tables for the scans:

1. The emission line set (except H_alpha)

[OII] 3727 [SII] 4075 HeII 4691 H beta [OIII] 5007 He II 5881 [OI] 6306 [OI] 6306 large scan H alpha [NII] 6590 [SII] 6730 [OII] 7331 [SIII] 9069 [SIII] 9539 HeII 10837

2. The old redshifted H_alpha filters:

H_alpha 6563 H_alpha 6607 H_alpha 6652 H_alpha 6700 H_alpha 6742 H_alpha 6789 H_alpha 6835 H_alpha 6877 H_alpha 6925 H_alpha 6970

3. The new redshifted H_alpha filters:

H_alpha 6565/45 H_alpha 6565/60 H_alpha 6595/45 H_alpha 6625/45 H_alpha 6655/45 H_alpha 6685/45 H_alpha 6715/45