Manufacturers: Astronomik

If you're observing under a light-polluted sky, taking your first steps in astrophotography using emission line filters is the best way to take great pictures. As a rule, a H-alpha filter is a sensible first purchase: with this filter, you can easily capture detailed images even if there is a full Moon or the sky is light-polluted! It is also the right filter for all nebulae that emit red light.

The OIII filter greatly expands your possibilities, because it also allows all green/blue structures to be captured in detail and in high contrast. Planetary nebulae and star-forming regions are especially worthwhile goals! Your HSO filter set is complete with a SII filter, and with these three channels you can create colour images like those from the Hubble Space Telescope!

(Text taken from Astronomik)

• MFR coating: the 12nm filters can be used on all devices up to f/1.4, the 6nm filters on all devices up to f/2.
• High-quality filter substrate: Astronomik filters consist of a stress-free, finely optically polished substrate, on which the actual filter is applied in the form of ultra-thin interference coatings.
• Homofocal finish: All Astronomik CCD filters are homofocal. For you that means: due to the very small thickness tolerance of the substrate, the focal point of your optic does not move when you change filters.
• Coating: Astronomik filters consist of up to 170 layers, which are applied to both sides to the substrate. These layers simultaneously form the actual filter and also serve as an anti-reflection coating.
• Durability: due to the special coating technology, Astronomik filters are completely scratch-resistant, moisture-resistant and do not age. Your Astronomik filter will continue to deliver for years to come!
• Integrated blocking of unwanted radiation over the entire spectral range from UV to IR. (You don't need an additional infrared blocking filter!)
• Supplied in a high-quality, durable storage box.

With an Astronomik filter, you get a top-quality accessory for capturing beautiful images with your instruments. You are investing in an accessory that will work reliably for many years, and will continue to deliver the pleasure you enjoyed when it was brand new, because the special coating technology ensures that the filter properties endure for years.

(Text taken from Astronomik)