Filter Optolong H-Beta 25nm 1.25" H-Beta 25nm 1.25" filter

Filter Optolong H-Beta 25nm 1.25" H-Beta 25nm 1.25" filter

A filter designed for visual observation of nebulae in large diameter telescopes.

The extremely narrow bandwidth of this filter provides maximum contrast, even under high quality skies. It is possible to observe the Horsehead Nebula in the constellation Orion with a 250 to 300 mm diameter telescope.

The Optolong H-beta filters are optimized for instruments with F/D ratios between F/4.5 and F/6. However, they can be used on instruments with F/D ratios between 3.5 and 15. The transmission loss and difference in filtering observed in some other filters with usual F/D ratios appears in the H-beta Optolong only on instruments with a very low F/D ratio (F/D 3 or less).

H-beta allows observation of very large objects as the filter is not only effective in the center of the eyepiece field; large field eyepieces are therefore perfectly usable. This filter should be used on instruments whose diameter is larger than 200 mm because, on small instruments, the little light passing through the filter does not allow a correct observation (even, in the worst case, no observation at all).

These filters are made of the best glasses available on the market: you will not observe any contrast drop in the stars compared to an observation without a filter.

The aluminum cell is manufactured by CNC machines that require extreme manufacturing precision. The cell is very thin, the total aperture is 26 mm for the 31.75 mm (1.25") version.

Use: Visual and photographic observation of nebulae (with modified or unmodified SLR cameras) and CCD cameras, using it together with an anti-IR filter.

Filter Optolong H-Beta 25nm 1.25" H-Beta filter