IDAS NB filters from Hutech have been specially developed for astrophotography
The NB2 filter is a dual-line pass filter that can be used with one-shot color (OSC) cameras such as DSLRs, mirrorless system cameras, or astronomical OSC cameras.
The NB2 filter lets the red H-alpha line and the blue-green OIII lines pass through and increases the contrast. You get narrow-band images with only one exposure series. The resulting images can be used to enhance the contrast of traditional RGB images or to create images in various common false color palettes.
The NB2 nebula filter does not block near infrared light. An IR cut filter is therefore recommended.
The most important features of the IDAS NB2 nebula filter:
♦ Allows for about 4x increase in exposure time
♦ Lets O-III and H-alpha pass
♦ Passbands slightly extended to longer wavelengths for still allowing the lines to pass in case of oblique incidence due to large angles, making the filter suitable for very fast optics
♦ Suitability for narrow-band imaging of diffuse emission nebulae and planetary nebulae
♦ High-quality anti-reflection coating
♦ Especially scratch-resistant hard coating
♦ Absorption of the urban scattered light (mercury, sodium vapor lamps, ...) and the nightglow
Exposure time extension - factor 4:
The IDAS NB2 allows exposure time to be extended by a factor of 4, but the most important lines in the deep-sky range (H-alpha and O-III) are transmitted up to 90%.
Put simply, you can expose about four times as long until the sky background comes through, but the object appears much stronger and more contrasty against the background than without a filter.
Difference NB1 - NB2 - NB3 Nebula Filters:
All three filters are suitable for color and monochrome cameras, DSLR and system cameras. A combination of these three filters allows extreme narrow-band images with mono and color cameras.
♦ NB1: Triple filter with transmission at H-Beta, O-III and H-Alpha. Furthermore, the filter blocks Near IR light, no additional IR cut filter is needed. The NB1 is the most versatile filter. We also recommend the filter for astromodified DSLR and system cameras.
♦ NB2: Dual band filter with transmission at O-III and H-alpha. The contrast effect is very strong. The filter is well suited for color astrocameras with built-in IR-cut filter and for photography with pure reflecting telescopes without corrector, such as RC telescopes.
♦ NB3: Dual band filter with transmission at in O-III and S-II. The contrast effect is very strong. This filter is ideal for the photography of objects that radiate in the S-II range (sulfur). These nebulae often still have an O-III component.
♦ NBZ: Dual band filter with very narrow passband of 5-6nm (ultra narrow band) in O-III and H-alpha for extreme contrast.
Astrophotographic results obtained with this filter on Astrobin
Here you can find some astrophotographs made with this filter type:
Link to Astrobin
