Mercury in the evening sky, Summer solstice
Due to the short nights, the observatory will remain closed at night in June. However, a few Sundays are planned on which the observatory will open between 14:00 and 16:00 for solar observation. The dates cannot be planned in advance due to the weather. The times will be announced via a ticker on our main page.

SUN AND MOON

The longest day of the year 2025 is on June 21. At 04:42, the sun reaches its greatest northern latitude due to the tilt of the earth's axis by 23.45 degrees. At 13:32 on this day, the sun is 64.18 degrees above the horizon in Zweibrücken. The length of the day is 16 hours and 23 minutes. From an astronomical point of view, it is no longer really dark at our latitude. Astronomical night only falls when the sun is lower than 18 degrees below the horizon. This is not the case between June 7 and July 4. We can look forward to long, bright days and, due to the full moon on June 11, brighter nights. However, the full moon in summer does not appear quite as bright as in winter. Its maximum height on this night is only 12.3 degrees.

PLANETS

The evening sky is poor in planets.

Mercury can be observed in the evening sky for the second and last time this year in the last half of the month. Its best observation days are between June 19 and 27.
Here is the view of the sky at 22:15 from the observatory hill.

Venus reaches its greatest angular distance from the sun on the 1st of the month at just over 45 degrees. It therefore dominates the eastern morning sky with its brilliance.

The red planet Mars is receding further from the evening sky. It is no longer an attractive object for visual and telescopic observation. On the evening of the 17th, it passes by Regulus, the main star of Leo, by only 0.8 degrees.

The giant planet Jupiter has withdrawn completely from the evening sky. It will gradually reappear in the morning sky in mid-July.

Saturn can be observed in the morning sky. The ring of the gas planet shows only a small aperture in the telescope.

Uranus was in conjunction with the Sun in the middle of the previous month and therefore cannot be observed.

Neptune is not yet a worthwhile object in the morning sky.

STARRY SKY

In the East the summer constellations have already risen. Among them are the Swan with the star Deneb, the Eagle with the main star Atair, which is still close to the horizon, and Lyra with its bright star Vega, which is also the brightest star in the northern sky. This means that the summer triangle, which consists of the three stars mentioned above, is completely above the horizon, even if it is not yet too high.

Deep in the South is Scorpio with its main star Antares, which means "opposite Mars". Because of its reddish color, it has already been confused with Mars, which is also reddish. The bright star to the west of Scorpio is Spica, the main star of Virgo.

The lion is already approaching the western horizon. Cancer is already on the verge of extinction.

High above us the inconspicuous constellation of Hercules can be seen. A little further to the southwest is the equally inconspicuous constellation of the Northern Crown and Bootes, which has also been called an ice cream cone because of its shape.

Low on the Northern sky the "celestial W" is Cassiopeia, wife of Cepheus, who can be found a little further west.

The following sky view is valid for June 1 at midnight, June 15 at 11 p.m. and June 30 at 10 p.m.

Due to the increasing length of the day, the useful observation times will be reduced from five hours at the beginning of May to just two hours at the end of the month. This would mean that the start of observations of galaxies and similar faint objects would shift from 23:00 CEST to 0:30 CEST. For this reason the observatory is only open from the beginning of May to the end of August under certain conditions. These include, for example Observation of the sun and moon on some weekends. The times are displayed via a ticker on our main page and our public WhatsApp channel announced.

SUN AND MOON

In the spring month of May, the day length for Zweibrücken increases from 14 hours and 46 minutes at the beginning to 16 hours and 4 minutes at the end of the month. The maximum elevation of the sun on May 31 is already 62 degrees.

At around 1:00 a.m. on May 4, the narrow crescent of the waxing moon will pass just over one degree north of Mars. The full moon on May 12 will affect the observation of fainter objects.

PLANETS

May is poor in planets.

The planet closest to the sun, Mercury, is in superior conjunction with the sun on May 30. It is therefore in the daytime sky. Superior conjunction means that the Earth, the Sun and the object, in this case Mercury, appear to be in line. The term upper and lower conjunction is only used for Mercury and Venus.

Venus continues to expand its position as the morning star. It rises around an hour earlier over the course of the month. However, the sun also rises earlier and earlier.

Mars is long past its best observation time, having been in opposition to the Sun in mid-January.

Jupiter gives its farewell performance in the evening sky. Towards the end of the month, it is barely visible to the naked eye. It is overtaken by the sun in mid-June.

Saturn is gradually reappearing in the morning sky, but is not yet a worthwhile object for observations.

Uranus and Neptune are still not observed.

STARRY SKY

Direction West the twins are already in the process of setting. Cancer can only be observed in the haze layers near the horizon, if at all possible.

A little higher up is the lion. In Greek mythology, the lion is often associated with the hero Hercules (Heracles). According to one source, it is said to be the Nemean lion, who was up to mischief near the city of Nemea and harassed the inhabitants there. The first of Hercules' twelve tasks was to defeat the lion. However, every weapon bounced off his fur, so the Greek hero had to face the lion with his bare hands in order to defeat him. From then on, the skin protected Hercules from his enemies. At Hera's request, Zeus moved the lion to heaven.

About us are the hair of Berenice with a multitude of galaxies, although a medium-sized telescope is required to observe them. A little further to the east is the Bear Keeper with its bright main star, Arcturus. A little trick makes it easier to find. If you extend the three pole stars of the "Big Dipper" in an arc, you will come across a bright star, Arcturus. To the left above the Bear Keeper is the inconspicuous constellation of the Northern Crown, where a nova has been expected since March 2024. See also the article Nova expected in the constellation of the Northern Crown. According to the latest observations, this should now appear by September 2025. Here are two graphics for orientation:

Next Eastbound you come across the inconspicuous constellation Hercules with its bright globular cluster M13, which is already a magnificent sight in binoculars. In the image above on the left.

Just above the southeastern horizon the summer constellation of Scorpius appears towards the middle of the month. The first summer constellations can be observed in the north-east.

Low on the northern night sky you can see the "celestial W", Cassiopeia, on the other side of the pole star as seen from the Great Bear.

The following sky view is valid for May 1 at midnight, May 15 at 11 pm and May 30 at 10 pm.

With the later onset of twilight, the opening of the observatory on Friday evenings in April is pushed back by one hour to 21:00 - provided the sky remains cloud-free.

SUN AND MOON

On the first of the month, the central star rises in Zweibrücken at 7:04 am and sets at 8:05 pm. The length of the day is 13 hours 1 minute and increases further to 14 hours 43 minutes at the end of the month. The full moon on 13.04. will affect the view of fainter objects.

From 10 p.m. on April 1, the waxing moon will appear to pass through the Pleiades above the western horizon. The Pleiades can be seen as a small collection of several stars or as a nebulous patch. Here is the view of the sky at around 22:30.

PLANETS

Almost all the planets have receded from the night sky.

Mercury almost reaches its maximum possible angular distance from the sun at 27.33 degrees on April 21. However, as it is 12 degrees south of the zodiac, it still remains too low for morning visibility.

Venus has begun its morning star period; in the telescope it can be seen as a thin crescent. On the 15th of the month, it crosses the horizon in Zweibrücken at 5:16 am.

The heyday of the Mars is over, it is no longer prominent in the evening sky. In the telescope it appears as a small disk.

Jupiter continues to dominate the evening sky. Its setting times are getting earlier and earlier, and its evening visibility is getting shorter and shorter as the days get longer and longer. On the 15th of the month it sets at 0:08 am, the end of civil twilight is not until 9:38 pm.

Saturn was recently in conjunction with (apparently near) the Sun. It cannot yet assert itself in the morning sky.

Uranus is no longer a worthwhile object of observation, Neptune stays in the daytime sky.

STARRY SKY

The spring constellations are now high in the sky. Only in the west are the remains of the winter constellations still visible. Above us you can see the spring triangle, which consists of the bright stars Arcturus in Ursa Major, Spica in Virgo and Regulus in Leo.

Deep in the South are the inconspicuous constellations of the Cup and the Raven and, to the south and west, the constellation of the Water Snake. In Greek mythology, Apollo, son of Zeus, once sent a raven with a cup to fetch water from a spring for an offering to his father. On the way, the raven was distracted by a fig tree whose fruit was not yet ripe. The black bird waited until the fruit was edible, ate it and only then completed his task. As an excuse for his delay, the raven bird grabbed a water snake and claimed that it had denied him access to the spring. Apollo saw through the lie and sent the raven, the cup and the water snake to heaven as a warning.

In the East another Greek hero, the summer constellation of Hercules, is already making his presence felt.

High on the northern night sky is home to the striking constellation of the Great Bear.

The following sky view is valid for April 1 at midnight, April 15 at 11 p.m. and April 30 at 10 p.m.

Due to the ever-later sunsets, the observatory only opens on Friday evenings in March from 7 pm. Provided the night sky is clear, of course.

Sun and moon

March has some astronomical highlights in store for us, including a partial lunar eclipse in our latitudes in the morning hours of March 14.

Entry into the penumbra occurs at 4:56 a.m., but is difficult to observe due to the small difference in brightness. The beginning of the partial phase is much more visible at 6:09 a.m. - at this time, however, the moon is only just under 6 degrees above the western horizon. In Zweibrücken, it sets at 6:55 am, while the total eclipse would not begin until 7:26 am.
Animation from the observatory hill.

Created with Stellarium 23.3

On Saturday, March 29, there will be a partial solar eclipse that will be visible for its entire duration.

To mark the occasion, the observatory will open at 10 a.m. on this day if the sky is clear. In Zweibrücken, the partial phase begins at 11:18 and ends at 12:59.
The following animation of the course of the solar eclipse was also created with Stellarium 23.3

Planets

Mercury offers passable visibility in the western evening sky in the first half of the month despite its perihelion (closest approach to the sun) on March 4.

Venus has had its best time as an evening star. It will remain visible until mid-March, possibly until the 20th of the month with bright optics. Towards the end of the month, it already appears in the morning sky.

Mars loses significantly in brightness over the course of the month, but remains high in the evening sky. A slight decrease in its brightness can be seen in the telescope due to the phase of solar illumination - by the end of the month it will shrink to around 90 % relative to its opposition position in January. Like the Moon, Mars also shows phases as we observe it from different angles from Earth. However, these phases are much less pronounced for Mars than for the Moon or inner planets such as Venus and Mercury.

Jupiter dominates the first half of the night and remains a conspicuous companion in the night sky.

Saturn is in the daytime sky together with the sun, it can no longer be observed.

Uranus and Neptune no longer play a significant role for observations. Uranus shortens its evening visibility considerably, while Neptune stays in the daytime sky and remains invisible.

Starry sky

The twinkling stars of the winter sky have already moved far beyond sunset. West but still remain striking eye-catchers in the night sky. At the same time, the transition to the spring sky is in full swing.

A look at North shows the circumpolar constellations that are visible all year round. High in the north-east is the Great Bear with the well-known constellation of the Big Dipper. Nearby is the Little Bear with the Pole Star, around which the inconspicuous constellation of the Dragon meanders. Cassiopeia and Cepheus can be seen in the northwest. A bright star can be observed from an elevated position just above the horizon: Deneb, the main star of the summer constellation Swan.

On Western sky you can still see some autumn constellations after sunset, including Andromeda.

In the South dominated by the impressive winter hexagon with its striking winter constellations: Gemini, Auriga and Taurus. Particularly striking in Taurus is the reddish Aldebaran, the "Eye of Taurus", which is sometimes mistaken for Mars. Among the Inuit, Aldebaran is called Nanurjuk and symbolizes a polar bear that was set upon by a group of dogs - represented by the Hyades, an open star cluster. In Inuit mythology, the hunters who want to hunt down the polar bear are the three prominent belt stars of Orion and the bright Rigel. Orion is also seen as a sky hunter in Greek mythology, followed by the constellations of the Great and Little Dog, the latter with Sirius, the brightest star in the night sky. The most prominent object in Orion is the well-known Orion Nebula, an active star-forming region. Some of its young stars, including the Trapezium stars, reach surface temperatures of around 50,000 Kelvin.

On Eastern sky the spring constellation of Leo gradually rises, followed by Virgo in the second half of the night. However, these constellations only unfold their full splendor in spring.

The following graphic shows the view of the sky on March 15 at 10 pm.