NPB 1.25" – DGM Optics™ Nebula Astronomy Filter - COSMETIC SECOND

SKU: NPB125CS

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.

Reviews & Testimonials

Excerpted from David Knisely on Cloudy Nights Telescopes Reviews.

The standard for many years for these filters was the Lumicon UHC filter, but now, DGM Optics and Omega Astrofilters have produced a new entry: the DGM Optics NPB ("Narrow Pass Band") Filter. It offers fine performance for a fairly modest price....I did like the view of the Veil just a bit more in the NPB than the UHC, and for M42, the difference was fairly noticeable for another reason: color! ... Overall, of the three narrow-band filters, I liked the DGM Optics NPB the best...The DGM Optics NPB Filter is an excellent narrow-band nebula filter which I recommend that nearly every amateur have in their eyepiece box. Read the entire review.

Review Astronomy Magazine

“Of the nine narrowband filters, I judged DGM Optics Narrow Pass Band (NPB) filter the best on emission and planetary nebulae. What sold me were the view I had of the Crab Nebula, the Little Dumbbell (M76), NGC 1514, and especially M42. The faint tendrils of M42 looked as though they were stretching outwards like fingers grasping at nearby stars.”
Phil Harrington, Astronomy Magazine, August 2005. See Astronomy Magazine’s filter review “Secret Weapons” in the August 2005 edition by Phil Harrington.

Review Mike Palermiti

Noted optical consultant Mike Palermiti conducted a blind test with the NPB Nebula filter and UHC type filters made by 4 well-known manufacturers and 15 participants with varying degrees of observing experience. Every one of the participants preferred the NPB over the 4 leading manufacturer's UHC type filter samples used in the comparison.

Spectral Curve

Measured spectral data for typical NPB filter

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 .5 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.