Astronomik 2″ H-beta filter
The Astronomik H-beta filter is a specialized narrowband filter designed for both visual observation and astrophotography. It is an excellent choice for anyone who enjoys exploring the deep sky. The key advantage of this filter is its near 100% transmission in the H-beta wavelength band, while at the same time blocking unwanted light from the rest of the spectrum. This dramatically increases the contrast of nebulae against the sky background - so much so that with this filter it is possible to observe the legendary Horsehead Nebula using telescopes with an aperture of 250 to 300 mm (10-12″). If you are looking for a filter that opens up the most challenging and rewarding deep sky objects, this is the right choice.
Optimal aperture ratio and aperture size
The optimal focal ratio for the Astronomik H-beta filter is between f/4.5 and f/6, with a usable range from f/3.5 to f/15. Light transmission losses and color shifts, which are common with lower quality filters, only appear with Astronomik filters at very fast focal ratios of f/3 and faster - a situation where almost any filter on the market would struggle. It is important to note that this filter is designed for telescopes with a minimum aperture of 200 mm (8″). Smaller instruments simply cannot collect enough light for meaningful observation with this type of narrowband filter.
Another practical benefit is full parfocality with other filters in the Astronomik range, meaning you do not need to refocus when switching between filters.
Optical quality and durability
The filter glass is precision optically polished, so placing it in the optical path of your telescope does not reduce image resolution or contrast in any way. The Astronomik H-beta filter is fully resistant to high humidity, mechanical scratches, and aging, making it reliable for use in demanding field conditions without any concerns about long-term performance. The filter is supplied in a high quality, sturdy protective case that keeps it safe during transport and storage.
About Astronomik
Astronomik is a German manufacturer with a long tradition, and their filters are recognized as among the best in the world. Every filter undergoes strict quality control and is produced from the highest grade optical glass with precisely defined transmission characteristics. The filters are designed to fully preserve the optical performance of your telescope while delivering maximum contrast on the target object - whether you are a visual observer searching for challenging objects under a dark sky, or an astrophotographer looking for detailed images of emission nebulae.
The parfocal design across the entire Astronomik range makes it easy to switch between filters without refocusing, which is especially useful during comparative observation or multi-filter imaging sessions.
Key features at a glance
- Near 100% transmission in the H-beta band
- Dramatically increases contrast of nebulae against the sky background
- Enables observation of the Horsehead Nebula with 250-300 mm (10-12″) aperture telescopes
- Optimal focal ratio: f/4.5 to f/6, usable range f/3.5 to f/15
- Minimum recommended aperture: 200 mm (8″)
- Fully parfocal with other Astronomik filters - no refocusing needed when switching
- Precision polished optical glass - no loss of resolution or contrast
- Resistant to humidity, scratches, and aging
- Supplied in a sturdy protective case
- Manufactured in Germany to the highest quality standards
Technical specifications
| Parameter |
Value |
| Filter size |
2″ |
| Filter type |
Narrowband - H-beta |
| Optimal focal ratio |
f/4.5 to f/6 |
| Usable focal ratio range |
f/3.5 to f/15 |
| Minimum recommended aperture |
200 mm (8″) |
| Parfocal with Astronomik range |
Yes |
| Suitable for visual observation |
Yes |
| Suitable for astrophotography |
Yes |
| Country of manufacture |
Germany |
