Amateur Astronomers Explores Venus with Baader SLOAN Filter

Even today, amateur astronomers can still contribute to scientific research. For example, Their new photometric filters now open another window into the depths of the atmosphere of the planet Venus.

Source: NASA/JPL-Caltech

Venus amazes researchers. It is as big as the Earth but extremely different from it. Venus is a hellish world with temperatures of up to 450 degrees at the surface. The reason for this is an enormously dense atmosphere, which generates a pressure that only exists at an ocean depth of 900m on Earth. This atmosphere consists of 90% carbon dioxide, a dense layer of sulfur dioxide clouds makes it opaque to us. There are only a few narrowly limited wavelengths in which a space probe camera or even a terrestrial telescope can hint at what lies beneath the cloud cover, which for the visual observer is simply brilliant white and contourless.

It has been known for some time that various structures in the clouds are visible in ultraviolet light. The US space probe Mariner 10 delivered the first images during a flyby in 1974.

Source: NASA/JPL-Caltech

They show the clouds at an altitude of about 60km.  It was not possible to go deeper with the technology of the time. With our Baader U-Venus-Filter (350nm) (various versions available), which is also called Venus filter, even astro-amateurs have been able to observe these UV structures of Venus with common telescopes for some years now. It was not until 1990 that the US Magellan Venus probe was able to map the surface of our sister planet in detail using radar. For the first time, a solidified world without seas and continents became visible, with numerous extinct volcanoes, but only very few meteorite craters in the highlands and lowlands.

The question of whether the very bottom of the surface can really only be explored with radar, or whether the infrared radiation of the hot rock can be recorded directly with appropriate technology, could only be answered decades after the Magellan mission. The best results so far have been achieved by the Venus probe Akatsuki. Its infrared photos show not only a completely overexposed day side of the planet but also the almost ghostly infrared glow from the depths of the planet on the night side – and above it the sulfur dioxide clouds as dark shadows.

Baader U-Venus-Filter (350nm). Credits: Baader-Planetarium

In 2021, images of the Parker Solar Probe gave an idea of how far we still are from a complete understanding of Venus’ atmosphere. On its way to the Sun, this probe passed Venus several times and delivered images with instruments that were actually intended for observing the solar corona. To the amazement of the scientists, photos of the night side of Venus very clearly showed the surface structures known from the radar scans of the Magellan probe – in the infrared part of the spectrum. This is thermal radiation directly from the surface of the rock. No scientist had expected these results. It is still a subject of discussion why the photos show the surface.

Source: Baader-Planetarium GmbH, Germany