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The IDAS D2 is a broadband filter which gives a mild reduction in light pollution.
Narrow band filters such as a Baader 7nm Ha and 8.5nm OIII are much better at cutting out light pollution and the result from the two filters can be combined to make a bi-colour image that is better than the IDAS D2. You can also add the Ha image to a broadband image.
An easy way to go is to use a dual band narrow band filter like the L-Enhance or STC Duo; these filters pass both Ha and OIII.
The narrower the filter passband is, the better it will reject light pollution. NB filters aren't useful on all objects but are very handy for emission nebulae under light pollution or when the moon is up.
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