Astronomik XT filters for wide-angle optics: With these filters, you can achieve beautiful star images right into the corners of the image, even with extreme wide-angle shots.
With other Astronomik filters, the image quality in the corners of the image is limited at short focal lengths (wide angle): Although the filters consist only of a one-millimetre-thick glass plate that carries the filter layers, this plate causes aberrations with certain types of short-focal-length lenses, and the stars are pulled apart into streaks.
Astronomik's XT filters are mounted on an extremely thin carrier substrate that is only 0.3 millimetres thick. This reduces "star streaks" in the corners of the image to a minimum.
The extremely thin carrier substrate of the XT filters is, of course, finely polished, stress-free and meets the highest demands of astrophotographers worldwide in every respect.
Despite this ultra-thin glass, Astronomik XT filters feature the same coating technology found in all Astronomik filters: completely scratch-resistant, moisture-resistant and non-ageing. The filter will retain 100% of its performance even after many years.
H-alpha: This filter is suitable for photographing hydrogen nebulae from areas with light pollution, but also from places with dark skies. The contrasts between objects that glow in H-alpha light and the sky background are greatly enhanced.
MRF-coating: thanks to the new MFRF coating technology, it is possible to use the filter on all devices up to an aperture of f/4.
Photography with narrowband line filters: If you are observing under bright skies, line filters are the best way to get started in astrophotography and take great pictures. An H-alpha filter is usually the first sensible purchase: with this filter, you can easily take detailed pictures even when the moon is full or the sky is very bright! It is also the right filter for all nebulae that glow in red light.
The OIII filter greatly expands your possibilities, as it allows you to capture all greenish/bluish structures in detail and with high contrast. Planetary nebulae and star-forming regions are particularly rewarding targets! With the SII filter, your HSO filter set is complete, and with the three channels you can take colour images like the Hubble Space Telescope!
The H-beta filter is not available in the 6nm version, as this filter has virtually no useful application.
Which half-width is the right one? When shooting under dark skies, images taken with a DSLR and even with many cooled CCD cameras are limited by the dark current of the camera and not by the background brightness of the sky. In this case, further suppression of the sky background by a lower half-width does not reveal any more details in the object! Compared to the 6 nm filters, the 12 nm filters have the advantage that they usually make it easier to find tracking stars with cameras that have a built-in tracking sensor!
If you have a camera with particularly low dark current and good cooling, the 6 nm filters offer all their advantages: Even stronger suppression of sky brightening allows even longer exposure times and thus even deeper images! Due to the low half-width, the stars become tiny, and faint stars disappear almost completely. Especially in Milky Way regions with many stars, the 6nm filters allow even faint objects to be displayed with high contrast without getting lost in the swarm of stars.
In short, we recommend using 12nm filters for DSLRs and all cameras with limited dark current.
The 6nm filters are the right choice in locations with strong light pollution, for cameras with extremely low dark current, and when faint objects require maximum contrast in the image!
A bit of help with your selection:
- As a first filter, we recommend the Astronomik CLS filter. This filter suppresses artificial light pollution and natural airglow. By using this filter you get a dark-sky background and can therefore use much longer exposure times to make fainter objects visible. The filter is optimised in such a way that objects are reproduced in their natural colours. Important: the simple CLS filter has no built-in IR-blocking. Therefore you will need the CLS-CCD filter for an astro-modified camera!
- A good choice for working in locations with really heavy light pollution is the Astronomik UHC filter. The transmission curve of this filter only allows the light of the H-beta, OIII, H-alpha and SII lines to pass through. The background suppression is significantly stronger than with the CLS, however this filter works only for gas nebulae! Star clusters and galaxies are largely filtered out.
- For a more in-depth introduction to astrophotography, we recommend the OIII, H-alpha and SII emission lines filters, available with full width at half maximum of 6nm or 12nm. With these filters you can create detailed images of faint objects even from locations with extreme light pollution and a full Moon high above in the sky. Images in these narrow emission lines are not naturally coloured.
- For the owners of astro-modified cameras we offer the Astronomik OWB filter: OWB stands for "original white balance". The filter corrects the displaced colour reproduction of a converted camera so that it can also be used for normal every-day photography, without having to revise every image on the computer.
Please note: In principle, all camera lenses can be used with the Clip-Filter - i.e. Canon EF lenses or camera lenses from other third party manufacturers such as Sigma, Tamron, Tokina, Walimex etc. However, the use of clip-filters with Canon EF-S lenses is NOT possible!
