Since February 2020 I have been documenting Venus regularly with my C11 EdgeHD and the Baader FFC Flatfield-Converter. Before each image session I recorded RGB data with my smartphone and shared a live image of Venus on Instagram (@sebastianvoltmer), which delighted planet fans every time, since only a few have the opportunity to see a Venus crescent in the daytime sky.
Especially exciting was of course the extremely close lower conjunction to the sun on June 3, 2020! Already about 10 days before, overlapping horns showed up. But since the sun shone into the tube, the contrast was not optimal. An improvement was possible with a self-built umbrella, which immersed the telescope opening in the shadow. So the local tube-entry was also noticeably reduced. I could increase the sharpness even more by wrapping ice bags around the tube. Three days before the conjunction to the sun an almost complete Venus ring formed, which is caused by the backward illuminated Venus atmosphere.
The sun already hit the main mirror, but fortunately (under constant control) the light just passed the secondary mirror, so nothing was damaged. Until 31. May I could observe with the SCT in this way. On June 1st, however, my proven traveler from Astro-Physics had to go in. With the 4″-refractor a narrow Venus ring could be made visible in the bright sky with the close proximity of the sun. The sky blue could be suppressed effectively with the Baader red filter RG-610. When Venus was less than 2 degrees away from the sun, the light irradiation from partly direct sunlight increased, so that it became a real challenge.
The pollen count turned out to be a big problem. In the glaring light it teemed with bright spots, so that Venus was seldom free of disturbing influences. Even faint cirrus in the predominantly transparent sky made Venus disappear immediately in the picture. I thought about longer exposure times in order to create a motion blur of the pollen – the seeing was good enough. Then I had the idea to continue the documentation with a Baader Herschel prism. Due to the light attenuation of the prism in combination with an ND 1.8 filter, the exposure times of the video frames could be increased significantly and I was able to observe more reliably. Together with Venus I approached the sun up to 35 arc minutes – until the weather changed. This was the most extreme observation I could make thanks to the technical means.
After the difficult evaluation of the video files and the hand-selected individual images, it became apparent that the Venusian arc showed irregularities in the light intensity. Through a call in the social networks planetary researchers made themselves known, which expressed the assumption that there are local pressure changes in the upper layer of the atmosphere, which result in a different aerosol occurrence in the Venus atmosphere. To make such fine differences visible from Earth in extreme proximity to the Sun is extremely fascinating.