Transit of Mercury on 9. May 2016

In just over one weeks time, Mercury will pass in front of the Sun. Although Mercury only covers 0.004% of the surface of the Sun, this is a rare event and hence worthwhile to have a closer look at, although you should, of course, never “look” at the Sun directly without proper protection.

As only one of three bodies in the solar system (this is ignoring a vast number of tiny rocks and asteroids orbiting the sun in an orbit smaller than Earths orbit), Mercury is able to pass in front of the Sun. But while the Moon treats us with a (partial or total) solar eclipse, and Venus presents itself as a well visible black dot during a venus transit, Mercury is farthest away from the Earth and is hence fairly smal. Here is an image of the last  Transit of Mercury in 2003:

Merkur (oben links) vor der Sonne am 7. Mai 2003
Mercury (upper left) in front of the Sun on 7. May 2003.

The image was recorded using a 90mm maksutov telescope with 1250mm focal length on slide film.

Graphischer Verlauf des Merkurtransits.

Graphical illustration of the transit.

With a well protected telescope, one can see Mercury starting to nibble at the sun at 13:12h CEST for about three minutes, after which the whole of Mercury is visible in front of the sun. At 16:56h CEST Mercury is closest to the center of the Sun and heads again for the rim, which he will reach at 20:37h and after another three minutes, at 20:40h, Mercury will have left the disk of the Sun. At that time, the Sun almost sets in Aachen, but is still three degrees above the horizon. For exact times, CalSky is a very good tool to do the calculations.

Due to the tiny diameter of Mercury, the transit is not visible to the (well protected) naked eye. If you do not have the proper equipment to pbserve the transit yourself, there are many events in and around Germany where you can enjoy the transit under professional assistance. And of course, there will be an event at the Sternwarte Aachen.

If everything fails, there are some livestreams, e.g. at the Peterberg in the  Saarland or, possibly the safest option regarding weather, the NASA stream with images of the solar observatory SDO:

Fingers crossed for perfect weather like in 2003, when the transit was perfectly visible here in Aachen.

EDIT: Here is another list with observations in the German area:

and for the rest of the world:

Total lunar eclipse 28. September 2015

What an eclipse! The total lunar eclipse on the morning of 28. September 2015 was visible from Aachen with perfect weather conditions.

Most images were acquired using my 114mm Newton (f 7.9) or my 70-200mm/2.8 telephoto lens. All images can be seen at: The descriptions are in German, but you don’t need these for admiring the images.

International Sidewalk Astronomy Night 8 – ISAN8

The next, eighth, International Sidewalk Astronomy Night, ISAN8 will be on the 28. of March 2015 as announced by the Sidewalk Astronomers.

The last ISAN7 was fully in the honour of the just deceased John Dobson and was a great success e.g. in Aachen, Bonn, Ingolstadt or Berlin. Which was also due to the great weather in most places.

Sidewalk Astronomy at Aachener Elisengarten 2014

However, the date for 2015 is only one week after the Solar eclipse on 20.03. and the Astronomy Day on the 21.03. and is hence somewhat challenging for the contributing astronomers. As most visitors of the astronomy day are already interested in astronomy to at least some extend, these differ from the majority of people who are targeted by the sidewalk astronomy actions. The latter mostly people who are not yet active in astronomy. Especially for those persons whose interest in astronomy is activated by the ISAN, the opposite arrangement of dates would be preferable. In that case, the ISAN would be some sort of advertising for the much more coordinated events of the astronomy day in Germany, Austria, Switzerland and some bordering countries and, at least this year, for the solar eclipse on the 20.03.. This, however, is not possible for 2015 any more.

Although it is not ideal to split an international activity on different dates for different parts of the world, it might be good to consider having a different date for Europe and the Americas. In my opinion, a separate, later date for Europe would be preferable. Probably on a Saturday before the Lunar eclipse on the 28. September 2015? I would love to read more comments on that topic in the comment section!

Noctilucent Clouds over Europe

Last night (03./04. July 2014) there was an impressive display of Noctilucent clouds visible above the northern horizon over many parts of Europe. These clouds with an altitude of approximately 83km were visible over Europe all night.

NLC 03.07.2014 21:05h UT, Aachen
NLC am 03.07.2014 um 21:05h UT in  Aachen
NLCs am 03.07.2014 in Aachen
NLCs am 03.07.2014 in Aachen

My images of last night can be found in my Fotowald / Photoforest. More images can be found e.g. on Spaceweather or on numerous German websites which are linked in the German version of this article.

I also tried to record a timelaps of the NLC movement. 300 images with an exposure time of 5s were taken every 8s between 21:04h UT and 21:45h UT. For this quick and dirty version I used the same settings for all images. In general, there is plenty of room for improvement though.

Time lapse movie of the NLCs of 03.07.2014 – 04.07.2014 between 21h UT – 21:45h UT.



C/2012 K1 PanSTARRS

On the evening of 9.5.2014 I finally caught the new PanSTARRS. After finding it visually with the 8″ 3000mm Refraktor of the Sternwarte Aachen I also caught him on CCD.

Unfortunately. the guiding was not quite right, so I had to stick to exposure times of 15s. The image consists of 50 individual frames à 15s and 6400 Iso fat the refraktor. Stacking was done using Fitswork. I first stacked on the stares and then manually shifted the individual frames to account for the motion of the comet (Details e.g. in Jans Tutorial Part 1 and 2). In addition to the short exposure time, mist and moon did no good as well. But at least I got him!

C/2012 K1 PanSTARRS

Announcement: International day of Astronomy – 5. April 2014

The Day of Astronomy on Saturday 5. of April is almost there. The Sternwarte Aachen, is, as every year so far, taking part and will have their doors opened from 15:00h until ‘open end’. A number of talks and experiments will complement the observation of the Sun, the Moon and other astronomical objects throughout the day. In addition to the 8″ main refractor, a number of amateur telescopes will be also available for observation.

Impressions of the Astronomy Day 2012 can be found here.

Tag der Astronomie 2012

“Sidewalk Astronomy” in Memoriam of John Dobson

In memoriam of the recently deceased amateur astronomer John Dobson, who died aged 98 on 15. January 2014, an International Side walk Astronomy Night (ISAN), i.e. a public observation, was announced by the Sidewalk Astronomers. John Dobson is known mainly for his invention of the Dobsonian Telescope and for being a co-founder of the aforementioned Sidewalk Astronomers. The latter set up their telescopes in a spot with many casual observers, who are invited to join the observation.

A couple of amateur astronomers from the Observatory in Aachen (Sternwarte Aachen) took part in this event on 08. March 2014 in the Elisengarten in Aachen.

Participants of the ISAN in memoriam of John Dobson.
Participants of the ISAN in memoriam of John Dobson.

During perfect weather, the Sun and the Moon were visible and could be observed with a large number of different telescopes.

More photos of the event can be found at: