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NPB™ 1.25" diameter – DGM Optics™ Narrow Pass Band Nebula Astronomy Filter.  Parts are provided in a standard 1.25 inch diameter threaded eyepiece ring.

Description

 

The NPB (Narrow Pass Band) filter is an Ultra High Contrast type of filter that is very effective for small and fainter emission and planetary nebula and a variety of bright nebula, especially through larger scopes. Another nice feature of the NPB filter is the very natural coloration yielded by this UHC type filter. Star images retain a much more natural color, in addition to pinpoint star images. High transmission at the 656.3nm Hydrogen Alpha emission line is a bonus for this design.

 

Specifications

 

This DGM Optics custom designed filter is well suited for a variety of telescopes and objects. The filter design stresses maximum optical throughput utilizing state-of-the-art optical thin-film designs and materials.

This filter is a “first surface” hard oxide thin-film and is much more durable and long lived than laminated “soft film” designs used by several famous makers. They are also much less prone to the internal reflectance problems that plague laminated filters. Laminated filters can produce a very undesirable “doubling” of stellar images often with one of the doubles being red. Contrary to popular belief, this image doubling is not due to the red sideband component that many nebula filter designs produce, but in many cases is due to laminated glass not being exactly parallel to the protective cover plate after lamination. Many laminated filters display this annoying characteristic.

This filter averages around 1% transmission (optical density of 2) through the rejection region from 540 to 590nm, and average transmission greater than 90% in the passband, and greater than 75% at the 656.3nm H-Alpha line. The design yields a filter with a very symmetrical shape and high optical throughput, for maximum enhancement of nebula with a minimum of loss of stars in the field of view.

The substrate is B-270 and has measured total wavefront values of .25 waves. The combination of first surface optical thin-film technology and a polished, flat substrate enables this filter to be used with high magnification, a real plus for small planetary nebula.

 

Please be aware that it is within our capabilities to control when our parts ship.  We cannot control when the parts are delivered.  We typically use the USPS to keep shipping charges within reason.  This works very well for domestic shipments, however, it is not uncommon for foreign shipments to be held up in customs regardless of the shipping method and non-delivery can be guaranteed if you give us the wrong shipping address.  First Class postage and International Priority do not have tracking provided.  If some other means of shipping/documentation is desired, please notify us BEFORE payment is made.