TS 1,25" CLS broad band nebula filter for deep sky observation and photographyBroad band filter for city light suppression, also suitable for small aperture
This Clear Sky-(CLS)-filter is optimized for the visual observation and photography of deep-sky objects in urban areas. Artificial brightening of the sky background is nearly fully blocked while stars and nebulae keep their brightness. Contrast is enhanced.
In opposite to the UHC filter which only transmits narrow spectral ranges close to desired lines, a CLS filter just blocks the range(s) where undesired lines lie. As a result, there are the following differences between the filters:
a CLS filter transmits more light and is therefore better suited for smaller instruments from 60 mm, especially at higher magnification.
- CLS filter is more color-neutral, especially photographic.
a CLS filter is also effective for star clusters and galaxies, despite this is mainly the case in photographic usage.
an UHC filter provides, especially visually, significantly more contrast.
Therefore, CLS and UHC filter complement each other very well.
Fields of use
Observation of deep sky objects with telescopes from 60 to approx. 150 mm aperture
Astro imaging: background brightness is reduced significantly allowing doubling the exposure time.
Substrate fine optically polished with plane parallel surfaces
1.25" diameter and filter threads on both sides
The filter has two main transmission windows exactly there, where gas and planetary nebulae have their main spectrum:
[OIII] and H-Beta: approx. 95% transmission between 420 nm and 530 nm
H-Alpha: from 610 nm, the filter opens again and lets red light pass nearly unblocked.
1.25" CLS Filter
Protective plastic case
Broad band filter for city light suppression, also suitable for small aperture