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Dark Blue Colour Filter 31.7mm. 435nm BandPass
Item no. 2458302
SRP: £31.00
Warranty: 24 Months

Premium Coloured Glass Dark Blue Filter, 31.7mm. 435nm BandPass.

All substrates fineoptically polished. These filters by far supersede the mediocre quality of common „flame polished“ color filters.

Fineoptical polish and 2 mm thickness allows these filters to be inserted anywhere into the optical path without introducing astigmatism or other defects. For instance they can be used in front of a binocular viewer without degrading the image in any way.
Substrates are free of striae and planeparallel polished to within 30 seconds of arc. This eliminates any double images or ghosting due to wedge errors in the glass.

All filters have standard 11⁄4“ eyepiece filter threads, tested and optimized to fit allmost all eyepieces on the market. Each filtercell has a male as well as a female thread to allow stacking for narrower passbands or to combine with the Baader UV/IR-Cut-filter. The combination of the red 610nm (# 2458307) and IR-Cut-filter (# 2459207a), for instance, results in an extremely narrow H-á passband-filter – at an incredibly cheap price.

The filter cell features the largest clear aperture of any 11⁄4“ filter on the market – for complete freedom from vignetting at any focal length.
The front „crown“ incorporates milled notches, which makes handling and threading the filter an easy operation in the dark.
All surfaces are treated with a 7-layer Multi-Coating, featuring a mere 0.25 % residual reflection. It is the most elaborate coating ever applied onto amateur color filters, resulting in a filter free of any false reflections under any incident angle of light.
As mentioned on LIGHT(-transmission) is the hottest commodity for all planetary observation. Especially during high magnification work „enough light“ is the deciding factor for the recognition of subtlest planetary surface detail, much more important than a horde of different filters of mediocre execution.

Less is more:
7-layer MC-coatings not only provide a brighter image – most important of all – they prevent the softening effect of scattered light!
Scattered light kills exactly those sublest features in planetary detail that this filter business is all about.Painstaking attention to coatings and perfect optical figuring are simple reasons why the image contrast through these premium filters is so rock-hard.

All colour filters are planoptically polished for sharp images at high magnification and Phantom Coating Group (PCG) Multi-coated for maximum contrast: no reflections, scatter or dimming.



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