Antlia narrowband filters are designed to enhance the contrast. Contrast brings out faint features by reducing the background – the narrower the filter, the better. The point is that we keep the signal 88%T at the SII(671.6nm), OIII(500.7nm) and H-Alpha(656.3nm) line stable as the filter becomes spectrally narrower to ensure best Signal-to-noise Ratio and cut-off rate of OD3 (0.1%) is required to reduce interference from other wavelengths.
The Antlia SHO filter set is suitable for imaging of emission nebulas, planetary nebulas and supernova remnant from observation sites with light pollution and from dark sites as well, only allow 3.5nm bandwidth high transmission at a center wavelength. Extremely narrow bandwidth can effectively improve the contrast of the objects, at the same time, it effectively interference the light from other wave bands, especially artificial mercury and sodium lamps.
Extremely narrow bandwidth results in a small amount of light, we recommend you to use a large-aperture telescope and long exposure time to collect enough signals to obtain the details of those faint objects under the SHO ultra-narrow filter.
In the production process, we use very strict quality control standards. Each filter is individually tested and scanned to ensure that the product meets the parameters we need. It is particularly pointed out that starting from the selection of the substrate, we must control the tolerance of each substrate to a very high standard of + -0.05mm. As we all know, when light passing through optical materials, it will be refracted and the thickness of the glass will affect the length of light refraction. We allow Antlia filters to achieve parfocal by minimizing tolerance of +-0.05mm.
All Antlia Narrowband filters edge are blackened. This is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass. As edge blacken must be hand-made, it becomes very costly to us.
Last but not the least is that our cut-off rate has reached a very high technical data. Many users will be very concerned about how high our filter transmission rate is and ignore the cut off rate. It is a very important quality index, which is not mentioned by other many brands on market, because the accomplishment is very difficult, it requires very high-end equipment, constantly thickens the layers of coating and longer time and more cost to complete. The unwanted light from other wavelengths is cut off, leaving only a width of 3.5nm at appointed Center-Wavelength, so that we get the highest contrast and background is increased enormous. This results in an extremely dark background and minimizing halos around bright stars.
Application and Performance:
Ultra-narrow 3.5 nm bandwidths, designed for astronomy imaging；
Suitable for imaging of most emission nebulas, planetary nebulas and supernova remnant;
Many of our images of planetary nebula and supernova remnants are taken only with H-a and OIII filters;
With HSO-set of filters you are able to process your images like the ones from the Hubble space telescope;
High transmission of typically 88% the filter gives you an enormous contrast boost;
This filter does not brighten deep-sky objects, it blocks unwanted light from other wavelength and highlights the contrast.