Antlia Filters 50.8 mounted H-alpha PRO 3nm narrowband filter
Antlia Filters 65x65 mm unmounted SII 3.5 nm narrowband filter
Filter Clear Diam. 50mm Unmounted.
"The Clear filter (C) without blocking infrared has a transmission greater than 97% through the spectral region, transmission is reduced to 95% at 400nm only in blue. The filter C increases the luminance signal of 45% for Kodak sensor spacing and the like.
If your aim is to get to 22 magnitude combining long exposures in "" luminance "", this filter C is the best choice (the other is bypass the filter).
If your aim is to emphasize the bright colors of a galaxy, the filter luminance L, which is combined with spectrally filters RGB, is the best choice to eliminate the halo surrounding galaxies in the near infrared (NIR) .This choice is even more appropriate when using systems or with a meniscus lens or corrector plate.
If you have a refractor or a telephoto lens, remember that the filter C also passes the UV. For this many refractors little chromatically corrected, often require a filter "" minus violet "" or "" Fringe-killer "" to remove the optical dispersion in the region of short wavelengths (blue-purple halo around bright stars). A filter size L partially these wavelengths and this is the best choice if you are using these types of instrument.
All filters are parfocal Astrodon:
most frustration in ' astrophotography with CCD is that of having to find the correct firing position with the H-alpha filter: the narrow band filters keep out much light so you must use a very bright star to perfect focus. All filters Astrodon Tru-Balance L, C, R, G, B, H-Alfa, OIII and SII are parfocal on optics with focal ratio less than f / 4. Login This means you can adjust the focus by using a filter C or G, install a filter H-Alpha and immediately proceed with the acquisition. This is one of the key advantages of the Tru-Balance filters Astrodon that made them cosŕ¬ popular in a short time.
The thickness of the filter determines how it can be parafocality: Tru-Balance filters are dichroic filters with very resistant treatments deposited on a single glass substrate highquality. The reduced thickness (3 mm) of this substrate is controlled accurately with error +/- 0.05mm. The change from lot to lot is less than 0.1mm, measuring slightly less than the critical areas of focus of a system f / 5. On request it is possible to select within various batches filters with less variation and then get a set of filters that have the exact same thickness (prices on request). "
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