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SVBONY SV139 1.25-inch ND0.9 Neutral Density Filter
The SVBONY SV139 Telescope Filter provides a specific ND0.9 density, designed to fit any standard 1.25-inch eyepiece. This level of filtration reduces the overwhelming brightness of the Moon by approximately 87.5% (transmitting 12.5% of light), allowing your eye to perceive subtle rilles, crater walls, and ejecta blankets that are normally lost to glare.
ND0.9 Brightness Reduction: Comfortable Lunar Viewing
Observing the Moon, especially from the first quarter to full, can be uncomfortably bright through a telescope, causing your pupil to contract and washing out fine detail. The SV139 filter's ND0.9 rating darkens the view to a comfortable level without altering its natural color. This significant 87.5% reduction in brightness (an 8× reduction) is ideal for revealing low-contrast features across lunar maria and highlands.
A Threaded 1.25" Cell for Any Standard Eyepiece
The filter is housed in a threaded 1.25-inch cell that screws into any standard 1.25-inch eyepiece or filter wheel.
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What does ND0.9 mean for the SVBONY SV139 filter?
ND0.9 is a measure of optical density. It means the filter allows approximately 12.5% of the light to pass through it, effectively blocking 87.5% of the incoming light (a 3-stop or 8× reduction). This is a strong level of filtration, ideal for reducing glare from a bright or full Moon for visual observation.
Can I use the SVBONY SV139 ND filter for observing planets like Jupiter?
Yes, in larger aperture telescopes (typically 8" or more), planets like Jupiter and Venus can be bright enough to cause glare that obscures fine detail. The SVBONY SV139 ND0.9 filter helps cut this glare effectively, improving contrast on Jupiter's cloud bands or subtle features on Venus without affecting the planet's natural color.
How does the SV139 ND filter affect the color of the Moon?
It doesn't. The "ND" in the SVBONY SV139 stands for Neutral Density, which means it reduces the intensity of all wavelengths of light equally. This darkens the image without introducing any color cast, so the Moon retains its natural grey and subtle brown tones.
Will the SV139 1.25" ND filter work with my 8" Dobsonian telescope?
Absolutely. The SVBONY SV139 filter has standard 1.25-inch filter threads (M28.5x0.6), which will screw directly into the barrel of any standard 1.25-inch eyepiece you would use with your 8" Dobsonian. The ND0.9 density is an excellent choice for an 8" scope, as it provides strong glare reduction for lunar viewing.
When should I use the SVBONY SV139 ND0.9 filter instead of a weaker or stronger one?
The ND0.9 provides an 87.5% light reduction (12.5% transmission), making it ideal for medium-to-large telescopes viewing the Moon near its full phase. An ND0.6 (25% transmission) is better for smaller scopes or early moon phases, while an ND1.2 or ND3.0 provides extreme light reduction for very large apertures.
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| Brand |
SVBONY |
| Model |
SV139 |
| Filter Type |
Neutral Density (ND) |
| Optical Density |
ND0.9 |
| Light Transmission |
~12.5% |
| Barrel Size |
1.25 in |
| Filter Size |
1.25" mounted |
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SVBONY SV139 1.25-inch ND0.9 Filter
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- SVBONY 1-Year Warranty
