U-Venus Filter 1.25-inch
As the title says, this filter is for imaging Venus and its cloud structures, along with the clouds structures of Jupiter. This Antlia UV filter will make it possible for you to image cloud structures containing Sulfuric Acid, the Calcium-ii-K/ Calcium-ii-H features of the Sun, or do UV landscape photography for a whole new view of our planet.
Cloud details primarily reflect in the ultraviolet band which cannot normally be imaged using broadband filters. The Venus-U filter uses the latest dielectric interference coating technology to achieve high transmission efficiency and exceptional isolation of the critical UV bandwidths. The filter effectively blocks the contrast damaging frequencies beyond 400 nm which typically swamp the ultraviolet cloud details on camera sensors. This filter also minimizes halos around bright stars and increases their contrast.
Visible Spectrum Range is approximately from 400 to 700 nm wavelengths.
Transmission of Ultraviolet and very-deep-violet light is faint, but with this filter the UR-A light range (wavelengths between 320 and 400 nm) can be highlighted. The very-deep-violet and ultra-violet light is beyond the average human eye, (though a few can perceive it,) most can only see light around the 400 nm threshold and longer. As a result, this filter is not useful or advised to use for visual observing.
The U-Venus filter effectively blocks the contrast damaging frequencies beyond 400 nm which typically swamp the ultraviolet cloud details on camera sensors. It also minimizes halos around bright stars and increase contrast.
Light emitted in the 200 to 280 nm range and everything over 400 nm is blocked by this filter.
The Calcium-ii-K wavelength is a 393.3 nm. The longer Calcium-ii-H wavelength is at 396.9 nm and is harder to isolate because of its close proximity to a stronger visible line.
Use with the Antlia IR685 filter for Better Clouds on Venus
Use this filter combined with the Antlia Filters IR685 filter for even greater cloud detail. Click on the Gallery thumbnail images to expand. Then use [CTRL]-scroll-up for an even closer look.
This filter is NOT to be used for visual observations, specifically the sun or UV light sources.
Suggested equipment to use with this filter:
1) A monochrome CCD/CMOS DSLR camera or specialized blue-sensitive digital camera. Remove anything that keeps UV light from reaching the sensor. This includes the sensor's cover glass, internal UV-IR blocker, and for a DSLR, the built-in low-pass filter, (because this filter may attenuate transmittance of the critical ultraviolet band that contains cloud details). Astronomy cameras generally do not have these issues.
2) A telescope with an aperture of 5-inches or greater. (This is very faint light.)
3) Avoid using a flash or other artificial lighting for your landscape images. These lights may block any of the very faint UV transmissions, as will as their glass housings.
- The lower the frequency in the UV band, the longer will be the exposure to achieve sufficient signal in your image. The sensitivity of most sensors also decreases rapidly at shorter UV wavelengths.
- It should be noted that when using a DSLR to shoot ultraviolet flowers, the camera needs to be specially modified to remove the infrared cut filter inside the camera.
- In non astronomical use, the lighting conditions may block UV transmissions (e.g. the UV contents of electronic flash emission,) because of a combination of lower emission at shorter wavelengths and increased absorption by the glass of the flash tube.
- These factors combine together to require a substantially increased exposure time (for continuous UV sources), UV intensity, and ISO sensitivity as the wavelength decreases.
- Non-astronomical applications： Use for general UV photography (flowers, health of plants, insects, forensics, and medical imaging).
Antlia narrowband filters are designed to enhance the contrast
Contrast brings out faint features by reducing the background – the narrower the filter, the better.
Suitable for imaging the cloud structures around Venus, this filter can highlight the very faint details of UV band contained in these imaging objects.
Extremely faint light
The extremely short wavelengths of this band results in a small amount of light. Antlia Filters recommends you to use a large-aperture telescope and long exposure time to collect enough signals to obtain the details of those faint objects with the U-Venus filter.
Blocks other bands:
The unwanted light from other wavelengths is cut-off, leaving only the short wavelengths below 400 nm, so that they get the highest contrast and the background is increased enormously. This results in an extremely dark background and minimized halos around bright stars.
The Antlia Filters Production Process:
In the production process, Antlia Filters uses very strict quality control standards. Each filter is individually tested and scanned to ensure that the product meets the parameters we need. In particular, starting from the selection of the substrate, they must control the tolerance of each substrate to a very high standard of +/-0.05 mm. As we all know, when light passes through optical materials, it will be refracted and the thickness of the glass will affect the length of light refraction. Antlia Filters allows their filters to achieve parfocal by minimizing this tolerance of +/-0.05 mm.
All Antlia Narrowband filters edge are blackened. It is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass. As edge blackening must be hand-made, it becomes very costly to them.
Their cut-off rate has reached a very high technical data point. Many users will be very concerned about how high the filter transmission rate is and ignore the cut-off rate. It is a very important quality index. They keep the signal of 88%T below the 400 nm line. This makes it stable as the filter becomes spectrally narrower to ensure best Signal-to-noise Ratio, a cut-off rate of OD3 (0.1%) is required to reduce interference from other wavelengths. It is a very important quality index, and the accomplishment is very difficult, This process requires very high-end equipment, constantly thickens the layers of coating, add longer production times, and adds more cost to the completed product.
- Schott optical substrate.
- 1.25-inch (2 mm+/-0.05 mm).
- Surface Quality: 60/40 (Refer to MIL-O-13830).
- 2 sides fine-optically polished to ensure accurate 1/4 wavefront.
- 30 arcsec parallelism.
- Transmission ＞80%
- 2 sides Multi-layers anti-reflection coating.
- Single / Non-glued substrate.
- Filter Ring: 1.25-inch (M26*0.6 thread). Ultra-thin filter cell to minimize vignetting by maximizing possible clear aperture. Black Anodized Finish.
- Laser Engraving No Fading.
- Size: Mounted; 1.25-inch.