Light Pollution Suppression (LPS) Filters
Comparison Photographs

Back to Filter List


Placing Orders

More Comparison Photos

The following set of photographs illustrate the effect of the IDAS Light Pollution Suppression filter. The site from which these photos were taken is in Cerritos, California, a suburb of Los Angeles and right on the border between LA and Orange Counties, where there is heavy light pollution. The location is a backyard of a residence with sodium streetlights on two corners of the property, a visible traffic light 1 house away, and only a few hundred feet from a freeway and medium-sized shopping center.

The first set of frames shows a comparison of unfiltered, IDAS LPS filtered, and Lumicon Deep Sky filtered test shots. These were taken consecutively (all on the same evening) using a Televue Pronto and field flattener (f/7.2) on Kodak Elite II 100 slide film. To allow a side-by-side comparison, the frame comparison shot of the film strips was taken on a light table using a digital camera.

Click on the image for an enlarged view

The second set of comparison images shown below is a result of cropping and processing the 10 minute exposures out of the set above. Even better results can most likely be had by choosing optimal exposure times for each of the filtered images, and then combining multiple images in a stack. The set shown here were a first attempt (during a brief spell of good weather) to bracket the exposure. A good example of a properly exposed and processed image is on astrophotographer Mike Cook's web page.

Click on the image for an enlarged view

Note that both the IDAS and Lumicon filters have the beneficial effect of suppressing the blue halos resulting from the refractor's two-element objective.

The final comparison shots were taken without and with an IDAS LPS filter, but with a 50mm lens. With this wide a field of view, the shift in filter bandpass at large angles off axis becomes apparent. Clearly, focal lengths of longer than about 100mm are required to utilize the full 35mm frame with a light pollution interference filter.

Illumination of the foliage on the right side of the frame is from a sodium streetlight about 40 feet away, partially shaded by a tree.

Copyright 2000-2002 by Hutech Corporation and ScienceCenter.Net
For technical difficulties with this site email: