Light pollution suppression (LPS) filters are designed to suppress the common emission lines generated by artificial lighting, yet allow the important nebula emission lines to pass, thus enhancing the contrast of astronomical objects, particularly emission nebulae.
IDAS filters are developed for astrophotography
Unlike other light pollution suppression filters, IDAS filters are specifically designed for balanced color transmission using the IDAS unique Multi-Bandpass Technology (MBT) process. The balanced transmission allows color photographs to be taken with minimal color cast to broadband emission objects such as stars, galaxies and globular clusters. The comparison photos at right demonstrate (qualitatively) that the IDAS filter maintains better color balance than other filters which have been designed for visual use.
CCD imaging can also benefit, because although CCD imagers can already shoot through light pollution to some extent, including an LPS filter to the setup gives an added (signal-to-noise) edge.
Main characteristics of the IDAS LPS D1 stray light filter:
♦ Especially designed for DSLR and single-shot CCD colour cameras
♦ High quality anti-reflective coatings
Exposure time extension - factor 2:
The IDAS LPS D1 allows a 2x extension of the exposure time. However, 90% of the important lines in the deep-sky range (like H-alpha and [O III]) are transmitted.
Simply said, you can expose twice as long until the sky background brakes through, but the object appears clearly stronger and with more contrast than without filter.
Not only the contrast of H II regions and plantary nebulae can be sucessfully increased with the IDAS stray light filter, the balanced colour properties allows also photographing of star clusters and galaxies.
Make your own impressions:
Transmission curve of the LPS-D1 filter:
Compare the IDAS LPS D1 filter with others: