UV Schuler

Near UV filter that corresponds to the Johnson photometric serie. The U band reveals higher atmospheric layers as it's easily absorbed and scattered by most gaz. Therefore, the majority of planets are dark in that band, the absorbing element being the atmosphere (more often) or the surface (Mars, Mercury). The only exception are Uranus and Neptune whose albedo is not diminished in comparison with blue light.

Images of planet in near-UV show very different things from blue images. This filter is highly useful for the observer but its use requires technical skill as the quantity of light is very low.

This UV filter is closer to blue wavelenghts than others, and passes light in the longer UV band (350-400 nm). This gives a good quantity of light for an UV filter but the "UV effect" could be not as great as with other glasses.

- Study of high atmospheric layers
- Usable without the need of an additionnal IR-blocking filter.

- Very weak quantity of light
- Highly sensitive to seeing and sky transparency/altitude

Venus 31 august 2004 - Mewlon 210, ATK-1HS The UV filter is of course the most interesting for that planet. It gives high contrast images of the higher atmosphere in which an unknow UV absorber draws dark details that make clouds movements perceptible.
Jupiter 18 march 2005 - Mewlon 210, ATK-1HS The UV filter begins to be sensitive to the tropopause at 0,1 bar level, above visible clouds. This UV layer gives a scattered view of the cloud layers fully visible in blue light. Some red features remain very dark none the less, as the GRS. Contrarily to longer wavelenghts, the limb is bright.
Saturn 6 april 2006 - Mewlon 210, Lumenera LU075M Very interesting for Saturn, this filter allows a survey of long-term seasonal effects, as the brigh winter haze seen over the poles (here at north).
Mars 18 november 2005 - Mewlon 210, Lumenera LU075M The UV filter gives maximum contrast for white clouds by eliminating completely the surface details (except during opposition period where there are still visible). None the less a violet transmission like the W47 will give a similar effect with much more available light..