Quality Characteristics of the Astronomik Filters

Astronomik filters arose originally from the absolute and unmitigated frustration over the poor quality of the filters of a formerly established manufacturer. Through their heavily fluctuating transmittance values we never knew how well the filters would work with our telescopes. The glass used was generally so poor and the resulting image in the eyepiece so much worse that various authors of journal articles advised to remove the filter to see the finest details. After a particularly dewy (wet) night of observing when we accidentally wiped the coating off one of their filters our frustration was so compounded by anger that we decided to develop a much better filter ourselves.

More than 10years quest for ever better quality Astronomik has developed into a globally recognized brand of specialty filters for professional and amateur astronomy. Globally, our Astronomik filters are being used by leading astronomers for various observing tasks to filter instruments of all sizes (the largest telescope using Astronomik filters, has a mirror diameter of 8.3m)!

Astronomik filters are not a byproduct of a major filter manufacturer, but the result of the dedication and resources of a small, energetic team which is dedicated to design, manufacture, testing, and distribution. Our quality expectations are so high that production in the Far East is totally unthinkable: All Astronomik components are "Made in Europe". We maintain an ongoing dialogue with our customers and our suppliers to cover every possible opportunity to make our filters even better.

In the development of each new Astronomik filter the desired function and our strict quality criteria must be fully met. In general, to optimize and release a filter for sale here on our web site our design cycle is a grueling one to three years for each new filter!

In the ongoing production process, quality control plays a crucial role. We have documented each step in the production process for years and each step is still reproducible. Unlike some competitors, we do not shift quality control testing to you, our endcustomers. Each Astronomik filter is checked before packaging and a mirrored seal affixed to each box before it is shipped. The Golden Seal of "Astronomik Quality Control" assures you that your filter has received the maximum in quality monitoring and is your hallmark to joyful and successful imaging or observing!

Another Astronomik high quality standard includes the implementation of innovative ideas: Our latest innovation is The Astronomik Clip-Filter System:
Astronomik’s Clip-Filter System is a novel and extremely convenient method to use filters on your digital SLR (DSLR) while astro imaging. The Clip-Filter system was honored by the prestigious American magazine "Sky & Telescope" with its "Hot Product 2009" award!

Our Quality Claims in Detail:

Optimized Transmission Curves

Astronomik filters are a valuable complement to your telescope optical equipment train: The filters are optimized for maximum contrast in the eyepiece for visual observation of objects and on the chip of your camera for photographic work. Each filter’s transmission curves are designed so that you gain maximum contrast and brightness but also retain the subtle gradations in each object. The transmission curves are optimized for best contrast enhancement of telescopes with an aperture ratio of f/4 to f/15.

Using our filters with faster instruments is possible, but it requires the selection of an individual filter with a spectral curve matched to your system. Please contact us Contakt.



Astronomik filters use a glass substrate which is manufactured to the tightest specifications. They would be suitable for the use with very high power lasers! Astronomik filters are made with thin interference layers on both sides of a polished precision glass substrate. Due to our high standards Astronomik filters will in no way reduce the performance of your optical train.

Image of a star with a third party filter

Image of a star with an Astronomik filter

Image of a star with a third party filter Image of a star with an Astronomik filter


These are key points to consider because, contrary to common experience with other manufacturers’ filters, with Astronomik filters stars remain fine needle points of light!


Parafocal Explained

All Astronomik filters are parafocal. When changing filters, the focal point will not change; you will not have to refocus your eyepiece or camera. This is due to the high tolerance and very low thickness of the substrate. As a special order, and for a small additional charge, we can deliver a set of filters with a thickness difference of less than 1/100mm deliver. (Other manufacturers call this specification "impossible". They also designate filters with a thickness difference of more than 0.5 mm as parafocal.).


Contrary to mass produced filters made of colored glass, the substrate of Astronomik filters is not a filter because it is totally transparent. Astronomik filters are made by depositing thin dichroic layers on both sides of this substrate. If you note the specifications of non-MC-coated colored glass filters, there is a loss of light of ~9% at the glass/air boundary. Other manufacturers also have a practice of lowering the cost of their dichroic filters by placing the filter on only one side of the glass carrier material. By contrast, the Astronomik filter layers are deposited on both sides of the glass substrate to deliver the filter effect with an almost perfect reflection: Our normal filter series achieve a maximum transmission of up to 99.6%.

Shelf life

Have you heard the rumor that you must exercise extreme caution when using and storing your Interference filter? While this may be true of filters from other manufacturers this is not the case with Astronomik filters: The coating technique used on our Astronomik filters is also found in a similar process used for coating machinetool drills and cutters which makes our filter layers resist high forces, high temperatures, and chemicals. These processes assure Astronomik filters are completely scratch resistant, and moisture resistant too. With Astronomik filters there is no worry that the filters will become ineffective by losing their capacity in a few years. After many years of use your Astronomik filters will be an accessory which will be ready to give you the same joy you experienced many years earlier when they were new.  

Because of Astronomik´s extraordinarily resistant coating technology, our filters come with a 10year warranty.

IR Blocking

Unlike Visual filters, all Astronomik CCD Photographic Filters contain integrated IR Blocking filter layers which prevent fogging problems due to Infrared Radiation (IR)up to 1200nm.

Quality Control

As a testament to our high quality standards for each filter series and to be able to meet production, each production step is carefully controlled and documented. Moreover, each Astronomik filter has a serial number. If need be, we are able to go back and understand every detail of the production process for any particular filter. When you own an Astronomik filter you do not need to hope that somewhere in the Far East good glass was used, or the coating process worked well, or threads are machined properly. You can be sure that each filter was manufactured with the utmost care, control, and our Golden Seal of "Astronomik Quality Control" was placed on the outer box after the filter was packed!