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Telescope House January Sky Guide Pt 1

Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Telescope House January 2023 Sky Guide

Happy New Year to all our readers.  For those of us in the Northern Hemisphere, we are now past the Winter Solstice and the point the Sun sits at its furthest south in the ecliptic plane.  As the Sun marches relentlessly northward, days begin to get longer and nights shorter, but this will not be readily apparent for many of us for a while. Of course, exactly the opposite is true for readers in the Southern Hemisphere - now basking in the later part of their summer.  Wherever in the world you find yourself, there’s a lot to look forward to in the skies above us this coming year and we will be here to guide you through many of the highlights.

The Solar System

The Moon

Our natural satellite kicks off 2023 as a resident of Aries, as a 10 day old Waxing Crescent.  The first astronomical highlight of 2023 is the third lunar occultation of Uranus in as many months - but only for some.  Those who are situated further north than 52° will see at least a glancing occultation of Uranus.  Those further south than this, won’t.  Where you are located on our home planet will dictate if you can see the occultation or not.  If you are a little more northerly, then don’t miss this opportunity.  The event starts for most at a little before 10pm on the 1st and ends an hour later, at the maximum.  How long the occultation lasts very much depends off where you are  - the more southerly you’re located, the less of the lunar disk passes in front of the planet.  “First contact” of the occultation occurs on the unlit side of the Moon, which may favour the visibility of this particular event.   As we’ve covered in previous sky guides, the ease or otherwise of observing occultations of the outer gas giants very much depends on sky transparency and light scatter, as the Moon can easily drown out the fainter world, long before the occultation takes place.  However, if you have clear skies, powerful binocular or a telescope, try to catch this if you can.

The Moon about to occult Uranus, a little before 10pm, 1st January, as seen from 55 degrees North.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

The Moon then continues its trek northward, up the ecliptic (from a northern hemisphere perspective, at least), passing through Taurus, where it can be found in close proximity to the planet Mars, on the evening of the 3rd January - the two objects separated by around a degree.  The Moon becomes Full in Gemini on the 6th January - this is the most northerly Full Moon until December 2023’s, which is just marginally higher in the sky.

The Moon then begins its Waning cycle, heading south through Cancer, Leo and into Virgo, where it comes to Last Quarter Phase on the 15th.  

The Moon then spends the third week of January ambling through the more southerly of the constellations that the ecliptic plane crosses: Libra, Scorpius, Ophiuchus

and Sagittarius, until it meets the Sun in Capricornus and becomes New on the 21st.  After this point in time, it becomes an evening target, passing by Saturn and Venus on the evening of 23rd (though at just 5% illumination will potentially be challenging - though not impossible - to find).  

The latter stages of January find the Moon drawing higher into the sky (from a Northern Hemisphere perspective), passing through Aquarius, Pisces, Cetus, back into Pisces again and on into Aries, where it reaches first Quarter phase on the 28th.  We end the month with the Moon back in Taurus, flanking Mars, at a 10 day old Waxing Gibbous phase.


The early part of January finds a rapidly diminishing Mercury headed sunward, at +1.6 magnitude and just 13% illumination.  This will make it extremely difficult, if not impossible to find for many in the early evening twilight.  The planet reaches inferior conjunction - the position between the earth and the Moon, as seen from our perspective - on 7th January.  

After inferior conjunction takes place, Mercury reemerges as a a morning object - though it will be mid-month before it has gained in brightness and separation from the Sun to be observed at all.  During the latter part of the month, Mercury improves in brightness and gains altitude significantly,   By the time Mercury reaches maximum western elongation at the end of January, it will be shining at -0.6 magnitude, displaying a 6.7 arc second diameter disk, at 63% illumination.  Standing just over 8 1/2° altitude at sunrise (from 51° N), Mercury will be relatively easy to find, as long as you have a clear enough easterly horizon.

Mercury at greatest western elongation, sunrise, January 30th.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


Venus is slowly emerging from late 2022’s superior conjunction with the Sun and starts January off as a -3.9 mag target, 10.4 car seconds across and nearly 96% illuminated.  The planet stands a little over 8 1/2° altitude at sunset (from 51° N) - being separated from the Sun by just over 17 degrees.

By mid-month, not much has changed - Venus remains static in brightness from the month’s beginning and has barely increased its angular size.  The planet will now stand just under 12 1/2° altitude at sunset (from 51° N).

At the close of January, Venus has increased its angular size to just over 11 arc seconds, but is no brighter as a result. Now separated from the Sun by just over 24°, the planet will stand directly higher at sunset - over 17° (observed from 51° N).  As such, casual observers will probably start to notice Venus a little more towards the month’s end.  We are at the beginning of a very reasonable evening apparition cycle of Venus - the planet will peak in altitude around the late Spring and early Summer, though will really ramp up in brightness as it draws nearer to us after greatest eastern elongation, which it reaches in early June.  Early July will see the planet hit peak (but not the maximum possible) brightness of a dazzling -4.5 magnitude.  

Venus at sunrise, January 30th.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


Mars is still a respectable post-Opposition target for observation in January, but the 1st finds it at magnitude -1.2 - over half a magnitude fainter than at its peak in early December 2022, transiting at a little before 10pm (GMT).  As Mars is such a comparatively small world, it dips in brightness and angular size quite quickly after its closest approach to us.  As such, time is of the essence for observations.  The planet is high in the sky in Taurus and very well-placed it terms of angular separation from the horizon, maximising our chances for decent seeing conditions (for the observers in the northern hemisphere).  

Mars at transit point, 1st January. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

By mid-January, Mars has faded to -0.7 magnitude and now displays a 12.7 arc second diameter disk.  Fast forward to the end of the month and Mars has faded significantly to -0.3 mag, displaying a distinctly smaller 10.7 arc second angular size.  The 30th sees Mars being occulted by the Moon again, as it was last month.  Sadly, this event will not be visible from Europe, though those observers in parts of Mexico, the Caribbean and Central America will be able to enjoy it.


Jupiter is still very obvious in the south in the early evening and is still very bright at -2.4 magnitude, as the year begins.  A resident of southern Pisces, just on the border with Cetus, at just over 39 arc seconds diameter, Jupiter still dwarfs all the other major planets in the sky in terms of sheer size - hardly surprising, as it makes up over two thirds of the entire mass of all our solar system’s planets combined.  Jupiter reaches transit point in the early evening - at a little before 5.30pm (GMT) and will set at just before 11.30pm.

When we reach the 15th January, Jupiter has faded fractionally to -2.3 mag and now displays a disk diameter of just under 38 arc minutes.  It will transit at around 4.30pm (GMT) and set round 6 hours later.

By the end of the month, Jupiter has faded yet further to -2.2 magnitude, but still displays a healthy 36 arc second diameter angular size. The planet will transit at a little after 3.30pm (GMT) and sets just a little before 10pm.  As readers can tell, the window for observing Jupiter under the best conditions, during hours of true darkness, is diminishing as time marches on.  While we are still a little way off Jupiter’s next superior conjunction, which occurs in April this year, we should take advantage of our current opportunities for observing Jupiter easily, at a clement hour of the evening.

As ever, there’s plenty of interesting Jovian transit events to observe from Europe. There’s a good mutual Great Red Spot and Io/Io shadow transit, which begins around 4pm (GMT) on the evening of the 4th.  The 5th sees a less favourable Europa and GRS transit, which begins around 6.20pm (GMT).  On the evening of the 11th there’s another mutual Great Red Spot and Io/Io shadow transit, which begins at around 6pm (GMT).  On the 13th January, there’s a mutual transit  and shadow transit of Io and Ganymede, that while it occurs in daylight, should be quite easily visible in telescopes - if you can find Jupiter.  This mutual event starts at just before 12.30pm and ends just after 3.30pm (GMT), though Ganymede’s shadow continues to transit as the Great Red Spot comes into view at just after 5.30pm on the same evening.  On the evening of the 16th, there’s an easily-observed mutual transit of the GRS and Callisto, which will be in full swing as the sun sets at just before 4.30pm (GMT).  There’s another mutual Io and Ganymede transit on the evening of the 20th, visible as the sun sets at around 4.30pm (GMT). Europa and the GRS can be seen in mutual transit at sunset on the 23rd. There’s another mutual Io, Io shadow and Ganymede transit on the evening of 27th, with the GRS joining the party a little later - this event starts at around 7pm (GMT).  The 28th sees another GRS and Europa mutual transit,  starting at around 4.30pm (GMT).

Jupiter, Europa and Europa Shadow Transit, 4.30pm, 23rd January.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


We find Saturn a resident of Capricornus in January.  At +0.8 mag on the 1st, it is brighter than any star in its immediate surroundings and is thus pretty easy to find in the SSW as the Sun goes down.  Saturn always appears slightly yellow in colour - though this can be exacerbated by atmospherics, depending on its altitude above the horizon.  This can also aid ease of identification.  The planet stands just under 22 degrees above the horizon (from 51° N) as the sun goes down.  It will set at a little after 7.30pm (GMT), so the window for observation is relatively slim.  It is 15.8 arc seconds diameter on the 1st.

As the month progresses, the window for observations becomes shorter and shorter.  On the 15th, Saturn sets at a little before 7pm.  By the time we get to the end of the month, it will set at just past 7pm (GMT). Saturn stands 18° high in the SW as the sun sets on the 15th, (from 51° north).

Probably the highlight of Saturnian observation this month comes on the evening of the 22nd of January, win, Venus draws alongside the ringed planet in very close conjunction. The two bodies will be separated by a little under half degree is the Sun goes down. This will mean that both planets will be easily observable at reasonable power in telescopes And will certainly be very easy to find in binoculars. Conjunctions or simply line of site effects from opposition here on Earth. Both planets are separated from one another by a considerable distance: Venus being just under 230 million km from Earth and Saturn being just over 1.6 billion km distance, on the same evening. While there is no great scientific significance for this close pairing, it will certainly be a lovely sight to behold, if the weather is clear enough. The following evening, of the 23rd, will find Venus and Saturn separated by just under a degree, which while not quite as spectacular as the previous evening’s close conjunction, will serve as a useful backup to the main event, if it is clouded out from your location. 

Saturn and Venus conjunction, sunset, 22nd January.  Red circle shows 1/2 a degree field.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

By the 31st, Saturn sets at a little after 6:17 pm (GMT, as seen from 51° north), which is only an hour and a quarter after sunset. As such, by the time we get to the end of January, the window for meaningful observation of Saturn in the evening sky is very close to closing completely.  Get out as early as you can in January and enjoy what we have left of Saturn.

Uranus and Neptune

And the outer gas giants are both well placed for evening observations during January. Neptune, being the further west of the two planets can be found in Aquarius, not far from the much brighter Jupiter. At the beginning of January, Neptune will show a small 2.3 arc second diameter disc, shining at a muted +7.9 magnitude. Jupiter will sit just under 8 1/2° to the east of Neptune, across the borders in the constellation of Pisces. The proximity of Jupiter, will make Neptune’s position in the sky, considerably easier to find.  Though never attaining naked eye brightness, Neptune is relatively easy to detect in binoculars and will show a distinct blue colour, which becomes increasingly more noticeable the larger aperture instrument you use to observe it with.

Uranus and Neptune relative positions, 15th January.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Uranus, situated further east in Aries, will be in some ways easier to find due to its inherent brightness (in comparison to Neptune). Uranus’ is greeny-grey disc should be easily visible to those with decent binoculars, from a reasonable observing position and is technically bright enough to be seen with the naked eye, but only by the particularly keen-eyed, from exceptional locations. On the 1st of January, Uranus will be +5.7 magnitude and display a 3.7 at  second diameter disc. As previously reported, for those situated in latitude is higher than around 53° north, the 1st January will see the Moon occult Uranus, starting at around 10 pm and finishing a little after 11 pm (GMT). Unfortunately, for those observers situated to the south of this latitude, the occultation event will not take place, and Uranus will appear to glide just a little to the south of the Moon’s South Pole instead. Occultations of the fainter outer planets are always a bit of a challenge to observe, due to the glare and scattered light from the much brighter Moon. However, if you have a telescope or binoculars and an appropriately northern observing location, this will be an interesting event to witness. 

By the time we get to the end of January, Uranus has shrunk fractionally, to 3.6 arc seconds diameter, but is still the same brightness +5.7 magnitude. it will transit a little after 6:20 pm (GMT) on the 31st (as observed from 51° N). 


C/2022 E3 (ZTF) is expected to start January at around 8th magnitude. At the beginning of the month, the comet is a resident of Corona Borealis and better seen in the early morning sky, though as January progresses will move north through Bootes, Draco, Ursa Minor and on into Camelopardalis, towards the end of the month, brightening significantly as the month progresses and becoming circumpolar (from 51° N) from the 11th January.   

By mid-month, the comet is a resident of Bootes and will be have brightened by one magnitude, to +7.  From the middle of January, the comet really begins to accelerate through the nighttime sky, as its path moves it closer to us here on Earth. The last two weeks of January will see the comet move over 52° northwards and by the time we get to the 31st, it is predicted to be around +5.5 magnitude, hopefully making it a relatively easy binocular target from a reasonably dark observing site. The comet will be very far north in the sky through much of the latter part of the month, making it easy to observe throughout the night. 

C/2022 E3 (ZTF) path through January (comet position shown 1st January).  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

As ever, we must be cautious as far as comets are concerned, as they are notorious for disappointing. However, current observations of this target are positive and while it won’t be a world-beating sight, even at its best, it should certainly be an interesting target for most people to be able to observe.


The Quadrantids are the major shower of January and can be fairly numerous in ZHR, yet rather muted brightness-wise in comparison with the major showers of the year.  The Quadrantids emanate from the northern polar region of the sky around Bootes, Draco and Hercules, in an area of sky which used to contain the now-defunct constellation of Quadrans Muralis (the mural quadrant).  Possibly seeded by Minor Planet 2003 EH1, which may well be an extinct comet (first observed by Chinese astronomers around 500CE), the Quadrantids are numerous at their peak, sometimes reaching a Zenithal Hourly Rate in excess of 200 (though not all of these will be seen from a given location).  This year, the peak date of the Quadrantids  - January 3rd/4th - coincides with a nearly Full Moon, which rising at just before 2pm GMT (from 51 degrees N), will rather spoil the opportunity for observations, sitting in relatively nearby Taurus and not setting until just before 6.30am (GMT) on the 4th. The Quadrantids sometimes peak with major storms, but the cloud of debris from which it is seeded is often perturbed by the passage of the major planets, which can't be easily predicted.  This year’s shower is predicted to be somewhat less in terms of peak ZHR.  This, coupled with the Moon interfering with the view, means the Quadrantids will emphatically not reach their potential this year.

Click here for the Telescope House January Sky Guide Part 2 


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