All posts by Jim Knoll

Planets of the Month – June 2023

By Erich Karkoschka

Venus is at its greatest western elongation on the 4th, showing a half phase in a telescope. It is 40 degrees high at sunset and sets after 10 pm.

Mars is close to Venus, only 3 degrees ahead of it by the end of the month.

Saturn rises around midnight. Its rings are tilted by 8 degrees.

Jupiter follows Saturn 3 hours later.

Mercury has a poor visibility around 4:30 am.

The Moon is only 3 degrees from Venus on the evening of the 21st (summer solstice), a spectacular sight. Mars is also nearby. Venus might be seen naked eye long before sunset just to the upper right of the Moon.

Planets of the Month: May 2023

by Erich Karkoschka

Venus is at its best, 40 degrees high at sunset and not setting until 10:45 pm. The Moon is 4 degrees below Venus on the evening of the 22nd, a great sight. Good eyes can see the pair during the daytime, such as around 3:30 pm when Venus is 84 degrees high. On the 22nd, the Moon is 7 degrees to the west, on the 23rd, 6 degrees to the east.
Mars is in the vicinity of Pollux and Castor all month. On the 15th, they form an 11-degree long line of “stars” of similar brightness.

Saturn rises around 2 am.

Jupiter follow Saturn around 4 am during dawn.

Mercury is barely visible after the 24th when it rises at 4:15 am.

On the morning of the 7th, the Moon occults Jupiter from 4:18 to 5:11 am. It takes a minute each to cover or uncover Jupiter’s large disk. The disappearance is difficult to observe since the pair is only 2 degrees above the horizon, 10 minutes after they rise. The reappearance is difficult to watch naked eye because of bright twilight, just 14 minutes before sunrise. However it should look great in binoculars or a telescope. Interestingly, the shadows of Io and Europa will remain on the disk until well past sunrise but the air may be too turbulent to pick them out.

Planets of the Month: April 2023

by Erich Karkoschka

Mercury is visible well at dusk until the 19th. It even sets past the end of astronomical twilight around the 11th, when it is at greatest elongation from the sun. Afterwards, it shows a small crescent in a telescope.

Venus is high up at sunset and sets more than three hours later. On the 10th, it is only 2 degrees from Pleiades, a nice sight in binoculars.

Mars is very hight at sunset. On the 14th it passes only 9 arc-minutes from third-magnitude star Mebsuta in Gemini. Then it aims for Pollux, the brightest star in Gemini.

Saturn is visible just before dawn in the southeast.

The first minor planet (1) Ceres is an easy binocular object near the tail of Leo.

The moon is close to bright Venus on the 22nd and 23rd and then even closer to Mars on the 25th. It causes a hybrid (total/annular) solar eclipse on the 20th, visible in and near Australia. The same evening it can be spotted with binoculars in Tucson in bright twilight, with Mercury nearby. The moon follows with an almost partial lunar eclipse at noon on May 5th. We are only one year away from the total solar eclipse of April 8, 2024 with more than 4 minutes of totality going from Mazatlan in Mexico through Texas to the Great Lakes.

Planets of the Month: February-March 2023

By Erich Karkoschka
Venus becomes brilliant at dusk. Venus passes Jupiter at 1/2 degree distance on March 1st. This should be a great sight
Jupiter is getting lower in the western sky and will be visible at dusk until March 29th.
Mars transits 83 degrees high, going from Taurus to Gemini. It still has an 11 arc-second diameter, great for observing its features in a telescope. But, by the end of March, it only will be 6 arc-seconds. Its magnitude decreases from 0 to 1.
Mercury finishes its morning visibility on February 18th and starts its evening visibility on March 26th.
Uranus can still be viewed at more then 70 degrees altitude in Aries, but it sets earlier and earlier as the month progresses.
Ceres has its opposition on March 21st at magnitude 7 in the Virgo Galaxy Cluster.

Pallas moves 50 degrees south of the ecliptic in Canis Major at Magnitude 8.

Comet ZTF is fast moving at 6 degrees/day from Auriga to Orion at Magnitude 6. Best on February 6th. It will fade to Magnitude 11 by the end of March.

Planets of the Month: January 2023

by Erich Karkoschka

Venus is becoming a more obvious evening “star” since it sets past dusk by mid-month.
Saturn is higher in the southwest at dusk, but then gets passed by Venus on the 22nd at less than 0.4 degrees separation, the closest planet pair this year. The brightness difference of four magnitudes makes Saturn look unusually faint.
Jupiter follows higher with a transit (highest in the sky) just before sunset. On the 28th, Ganymede’s shadow is visible from sunset to 8:30 pm.
Uranus and Neptune are in the vicinity of Jupiter. Neptune is 8 degrees to the west of Jupiter, which is the current minimum. Uranus is 45 degrees to the east of Jupiter, but will get close to it this summer.
The month after a great occultation of Mars by the moon, we get another one with the same planet and very conveniently high in the evening sky. Mars will be occulted on the 30th from 9:44 to 10:51 pm, with the disappearance occurring at the dark limb so that the event is easy to watch naked eye. Disappearance and reappearance occurs gradually over some 15 seconds each time due to the 11 arc-second diameter of Mars. The reappearance is interesting to watch in a telescope.
Comet ZTF will get circumpolar at the end of the month and move at 6 degrees per day. Its brightness may peak at magnitude 5 at the last day of the month.

Planets of the Month: December 2022

By Erich Karkoschka

Saturn is still high in the southwest at dusk and sets late in the evening.
Jupiter follows higher with a transit at dusk and sets just past midnight. On the 15th, we can watch Ganymede’s shadow until 8:18 pm (MST). On the 22nd, Ganymede transits Jupiter’s disk until 7 pm with its shadow following starting at 9:44 pm. On the 29th, Ganymede transits from 8:11 to 11:07 pm. All these transits occur on Thursdays.
Mars reaches opposition on the 7th, at the same time as the Full Moon occurs. Furthermore the moon occults Mars! The event lasts from 7:32 to 8:27 pm, a great sight even with just your eyes. The disappearance and reappearance of Mars lasts almost a minute. Have your telescope ready for this rare event! Mars shows a polar cap and details on its surface quite well due to its 17 arc-seconds diameter.
Venus can be found in the southwest during early dusk.
Mercury joins Venus from the 6th to the 30th, to the upper left of Venus. The prettiest sight is on the 24th when the crescent moon is next to both planets.
Uranus is just past opposition and well placed almost all night.

Neptune is still observable during the first half of the night 6 degrees west of Jupiter.

Planets of the Month: November 2022

By Erich Karkoschka

Saturn transits 40 degrees high during dusk. Its rings are still open by 15 degrees, which will not happen again until 2028.
Jupiter rules the night, 40 degrees east of Saturn. It is so bright that it can cast shadows at a very dark site. On the evening of the 2nd and 9th, Ganymede’s large shadow wanders across Jupiter’s disk.
Mars is the bright orange “star” in the east during late evenings. Its rising times change from 8 pm at the beginning of the month to before 6 pm at the end. After the first week, it is even brighter than Sirius. Its disk reaches 17 arc-seconds diameter, which shows its surface details quite well in a telescope. On the 30th, Mars is closest to Earth. Its distance is better than at an average opposition, and its altitude in Tucson reaches 83 degrees. Hard to beat!
Venus will start its evening visibility in December, with good eyesight even during the last days of November.
Uranus comes into opposition on the 9th. At magnitude 5.6 and 74 degrees high in the sky at midnight, it is within reach of naked eye visibility if you know where to look.
Neptune is visible in binoculars 7 degrees to the west of Jupiter.
Vesta is as bright as Neptune, but 20 degrees to the southwest in Aquarius.
The Leonid meteor shower might have an intense outburst around 11 pm on the 17th. This is just when the radiant rises in Tucson, which means we would only see a few meteors grazing the atmosphere. If it lasts for an hour, when the radiant will be higher, we may be in for a treat.

Planets of the Month – October 2022

By Erich Karkoschka

Jupiter is the most obvious planet, shining brightly at magnitude minus 3 all night. It just had its closest opposition in 50 years.
Saturn is 40 degrees to the west of Jupiter. It is first magnitude in an area of the sky without bright stars.
Mars rises at 10 pm and later in the month by 9 pm. It outshines all surrounding stars of the winter constellations until Sirius rises in the morning. It becomes interesting to observers with a telescope as its diameter reaches 15 arc-seconds, sufficient to see its surface detail.
Uranus rises after dusk in the constellation of Aries. It can be found naked eye if you know exactly where to look and have fairly dark skies.

Neptune is a binocular object 10 degrees to the west of Jupiter.

Mercury is visible during dawn in the first three weeks of October. It is often a challenge when it becomes visible, but around the center of its visibility period it should be quite obvious around 5:30 am low in the eastern sky.
Vesta is at 7th magnitude and thus even brighter than Neptune. It finishes its retrograde opposition period in Capricornus.
The Moon covers two planets. It occults Uranus on the 11th from 9:54-10:29. Ingress and egress take about 12 seconds due to the 4 arc-second disk of Uranus. On the 24th, it occults Mercury after sunrise. Only specialists will be able to locate Mercury in their telescope, and the moon will be invisible as it is not illuminated. Mercury will suddenly dim over 10 seconds and then be gone.
Orionid Meteor Shower. Parent Comet: Halley’s Comet. Peak is the early morning hours of October 21st around 3 am. Some may be visible late evening on the 20th. Comets will appear to radiate from the constellation of Orion. Will need a dark sky to see very many (10-20 per hour).

Planets of the Month: July – September 2022

By Erich Karkoschka

Saturn is the first planet to rise at night, at 10 pm in early July. By the Opposition on August 14, it rises at sunset.
Jupiter is the second planet to rise, at midnight in early July. By the Opposition on September 26, it rises at sunset.
Mars is the third planet to rise, at 1 am in early July, but already at 10 pm by late September. It moves from Aries into Taurus, passing Aldebaran on September 7. It has brightened to zero magnitude. In a telescope, one can watch its diameter increasing from 7 to 12 arc-seconds.
Venus is the fourth planet to rise, at 3:30 am in early July, but close to 6 am by late September, which is not much before sunrise. This means Venus is leaving the morning sky by the Fall.
Mercury is the last planet to rise at dawn, visible until July 6. From Mercury to Saturn, all planets have been visible at dawn in the order of their distances from the Sun. All August, Mercury is visible low at dusk.
Neptune is visible in binoculars about 10 degrees west of Jupiter.
Uranus is rising at 2 am in early July, but 8 pm by late September. It moves slowly in Aries.
Vesta is an easy binocular object in Aquarius at 6th magnitude. Its Opposition is August 22.
The Moon has two beautiful approaches to Venus, on July 26 to 3 degrees distance, and on August 25 to 5 degrees distance. The latter one is visible only in bright twilight since Venus rises late.