What to look forward to in 2021
Find elusive Mercury – May
If you have never seen Mercury in the sky before, you may be surprised to discover that you’re not
alone – there are plenty of astronomers, even experienced ones, who have never seen it. at’s
because it is not an easy planet to see, often lurking on the horizon at sunrise or sunset, lost in the
Sun’s glare.
On occasions, however, Mercury tracks a little further away from the Sun than usual, and sits in a
brightish sky where, with a little care and patience, we can see it. I’ve always enjoyed hunting it
down when on early-morning dog walks, or having enjoyed a beautiful sunset. In 2021 I’ll look
forward to doing so again. e best time to see Mercury will be during evenings in May, as seen in
the accompanying diagram, when Mercury experiences its best eastern elongation, at least as seen
from the UK. On 17 May, Mercury is 22 degrees from the Sun and 10 degrees above the horizon,
with the Sun having set 40 minutes earlier, and shines at magnitude +0.3. You might be able to spot
Mercury even earlier in the month, from around 10 May when it is 16 degrees from the Sun and
shining at magnitude –2. If you’re having trouble locating it, then it often helps to triangulate from
more obvious signposts, such as bright Venus that will spend May evenings below Mercury in the
sky, or Capella in Auriga some 20 degrees above the innermost planet. Make sure you have a clear
west-north-west horizon too.
Plus, if you’re out of luck and unable to see Mercury in May, there will be a second chance later in
the year. Mercury reaches greatest western elongation in the latter half of October, achieving a
distance of 18.5 degrees from the Sun and 11 degrees above the horizon in the pre-dawn sky.
Keith Cooper
Looking forward to star parties – Throughout the year
While many of us are familiar with self-isolation when we observe during antisocial hours, it is a
true pleasure to spend time at star parties with fellow astronomers, and with the COVID-
pandemic hopefully coming to an end in 2021, being able to gather again has surely got to be one of
the highlights of the coming year.
ese events, normally held at a dark site around new Moon, are an excellent time to enjoy this
wonderful hobby. At night there is the chance to look through others’ telescopes, borrow accessories
and discuss nding new objects, while during the day there are trade stands, second-hand sales,
workshops and talks from experienced amateurs and professional scientists. No matter what the
weather, there is always something new to see or hear, especially while enjoying a beer and dinner
with old and new friends.
With 2020 seeing many star parties cut back or cancelled altogether, and club meetings reduced to
online events, I am looking forward to hopefully attending the Spring Star Party (9–11 April 2021)
and the autumn Star Camp (4–11 October 2021) at Kelling Heath in Norfolk. e spring galaxies
will be high in the sky after dark with highlights such as the Sombrero Galaxy, Markarian’s Chain
and the Leo Triplet. In the pre-dawn sky, the summer Milky Way will be rising. I can spend hours
getting lost in the stars through my 100mm binoscope, immersed in the depths of our Galaxy as the
eyepieces are lled with endless streams of star clusters, dark dust clouds and nebulosity.
While keeping my ngers crossed that 2021’s star parties do go ahead, my pitches for Kelling Heath
are now booked, and the joy of preparing equipment and writing an observing list begins.
Mark Radice
Summer’s shooting stars – August
It should be a great year for observing the Perseid meteor shower, with maximum night of 12–
August occurring only four days after new Moon. Good numbers of Perseids are also likely to be
seen throughout the second week of August.
Digital imaging may have made capturing images of meteors less difficult, but nothing compares
with the thrill of seeing a bright meteor shoot across your eld of view. e Perseids are rich in
bright meteors and around a third leave behind persistent trains.
To maximise the number of meteors that you see, choose as dark an observing site as possible with a
clear view of the sky. Don’t look directly at Perseus. You will see more meteors if you observe an area
of sky around 30 degrees from Perseus and around 50 degrees above the horizon. Observed rates
increase as the night passes as the result of Perseus climbing higher in the sky, so persistence should
pay off.
Nor does it all have to be about the meteors. During the gaps between meteors, you can see
satellites crossing the sky, while the Earth’s rotation will cause the spring constellations to head west
and the autumn constellations to climb into view in the east. If you stay out until the end of the
night, you can see Mira (omicron Ceti) close to maximum and, nally, Orion rising as morning
twilight arrives. Invite a friend or a family member along and chat to them about the night sky –
chatting will also help you remain alert.
Tracie Heywood
The return of Comet 67/P – November
I’ll be brushing up on my pronunciation of Russian names, as my highlight for 2021 is the return of
Comet 67/P Churyumov–Gerasimenko. is is the comet we know more about than any other,
thanks to the Rosetta spacecraft that investigated it for over two years before impacting on it in
- is will be the comet’s rst return to perihelion, and proximity to Earth, since then.
67/P is a Jupiter-family comet, discovered in 1967 by the two Soviet astronomers whose name it
bears. Its distance from the Sun varies between 5.7 and 1.2 AU (852 million and 180 million
kilometres) over an orbital period of 6.4 years. Perihelion will be on 1 November, and closest
approach to Earth on 5 November, when it will be 0.42 AU (62.8 million kilometres) distant. It will
be very well placed for observation from the UK throughout the latter part of 2021, moving through
the constellations of Taurus, Gemini and Cancer.
Comets are inherently unpredictable in brightness, but it could be the brightest comet of the year,
attaining magnitude +8, making for a good object seen through large binoculars and all telescopes. It
will be worth monitoring for activity. Rosetta observed collapsing cliffs of ice; such events near
perihelion would likely cause observable outbursts. A fracture in the neck between the two lobes of
the nucleus was also seen to grow. If the comet split, that would be very interesting. We can wonder
and imagine how the dead spacecraft and its Philae lander are faring on the surface, as we turn our
telescopes to this familiar icy visitor.
David Arditti
A spring crescent Moon – March, April and May
In 2021 I am looking forward once again to the sight of the waxing crescent Moon in the evening
sky during the spring months of March, April and May. At that time of year the ecliptic makes a
steep angle with the western horizon after sunset, which means that the crescent Moon rides quite
high in the sky after sunset.
Not only is this a harbinger of better weather to come for those of us in the Northern Hemisphere,
but it also provides the best conditions for seeing the beautiful phenomenon of earthshine, or ‘the
old Moon in the new Moon’s arms’, where the Moon’s night hemisphere glows dimly as a result of
re ected light from Earth. Careful examination of the Earth-lit portion through binoculars or a
small telescope will reveal some of the brighter craters such as Tycho, Copernicus and Aristarchus
glowing in the earthshine.
is is also the time to look out for impact ashes on the Earth-lit hemisphere, caused when
meteoric particles travelling at great speed strike the lunar surface. e resulting release of energy is
bright enough to create an instantaneous ash visible through amateur telescopes. Of course, the
chances of looking in the right spot at the right time are quite small, but modern high-speed γ video
cameras have a better chance of recording any activity and there is software available that will scan
video les for potential impact ashes.
Even the casual visual observer has a small chance of catching an impact ash, but if you are
seriously interested in pursuing this kind of observation then you are recommended to contact the
Lunar Section of the British Astronomical Association for further advice.
Bill Leatherbarrow
A partial eclipse of the Sun – June
On ursday 10 June, 2021, we will be treated to a partial eclipse of the Sun. While these don’t have
the heart-stopping beauty of a total solar eclipse, it’s worth viewing the event to see the Moon’s
silent journey as it slowly edges across the Sun’s disc. As with any solar viewing event, great care must
be taken to protect eyesight and equipment. Ensure that any solar lters are securely attached to the
front end of the telescope and any nder-scopes are rmly capped. And of course, DO NOT look at
the Sun through binoculars or a telescope without dedicated lters.
Inexpensive white-light lters are ideal for partial eclipses. If conditions are good, I hope to use my
venerable ousand Oaks full-aperture lter to view the eclipse, which hopefully will also capture
any sunspots that are visible. Coupled with a DSLR you’ll be able to check focus and exposure to
ensure good results. e eclipse begins at 10.10am BST for my location in North Essex, with the
maximum eclipse occurring at 11.15am BST. e eclipse ends at 12.24pm BST. You can check the
speci c details for your own location using the excellent website timeanddate.com, which also shows
a neat graphic of the event. It also has a somewhat-grim statistic stating that since the year 2000
this day has been cloudy 80 per cent of the time.
Nik Szymanek
Super-speedy astronomical cameras
I dream of faster deep-sky imaging. A dual rig comprising two parallel telescopes halves the
integration time but at considerable cost. At low resolution we’ve had great results this way, but
exure at long focal lengths is defeating us. Fortunately, I now spy another way of cutting exposure
times dramatically.
Yves Van den Broek recently invited me to process a giant, thirty-two pane mosaic of the Cepheus
region taken with his 106mm refractor and a modern QHY CMOS (Complementary Metal Oxide
Semiconductor) one-shot colour camera. Each image had just ninety minutes of total exposure. In
deep-sky imaging terms, that’s a snapshot – and yet the data were sensational, deep and clean. e
CMOS camera has re-written the rule book, I suspect, and has made one-shot colour imaging more
attractive, but wait – there’s more. It is now possible to buy dual bandpass narrowband lters for one-
shot colour cameras, meaning that hydrogen-alpha and oxygen-III can be captured simultaneously.
A ne image of Outters 4, the Squid Nebula, caught my eye recently. Imager Göran Nilsson had
this elusive feature showing clearly in just a couple of hours, admittedly in fast optics, when my own
results with an O-III lter and monochrome CCD did less well in eleven hours – and Göran had a
colour image as well from his two hours.
I hope, therefore, that 2021 will see CMOS cameras come into their own and grow more popular
among imagers. As for me, I aim to spend 2021 processing more data from my new one-shot colour
CMOS camera and multiple narrowband lter.
Olly Penrice
Watch a Trojan block a star – December
roughout my 45-year-plus observing career, I’ve been fortunate to watch asteroids occult (pass in
front of ) stars many times, but I’ve yet to observe a minor planet hide a naked-eye star. Fortunately,
such an event occurs on 16 December 2021 as seen from the UK, so I’m making this my 2021
astronomical highlight.
Despite the two million lumps of rock larger than one kilometre in diameter that are believed to
inhabit the Asteroid Belt between the orbits of Mars and Jupiter, plus an unknown number of trans-
Neptunian objects, the sight of such bodies occulting a bright star is still a rare event. e narrow
track projected on the Earth’s surface is no wider than the occulting body itself, and the duration of
the occultation may be just a few seconds long.
So, I’m hoping that observers (myself included) who live in a vast swathe that tracks across the
country (see the diagram above) will have clear skies when a 68-kilometre-wide Jupiter Trojan
asteroid (an asteroid that orbits at the same distance as Jupiter, in one of the giant planet’s
Lagrangian points) known as 11395 (1998 XN77) passes in front of a magnitude +5.5 star called
HIP 12148 in the constellation of Cetus, between 21h 14m 20s and 21h 15m 20s Universal Time
(9.14–9.15pm GMT) on ursday 16 December.
HIP 12148 (RA 02h 36m 34.9s, Dec +07° 43’ 48′′) is fortunately situated close to the southern
meridian, halfway from the horizon to the zenith for UK-based observers at the time, but a 12.7-
day-old waxing Moon in Taurus lies less than 22 degrees away. I recommend nding a rural location
and attempt viewing the star through a long cardboard tube to block out the moonlight. At the right
location and time, HIP 12148 will appear to vanish for almost eight seconds as the asteroid hides it.
Ade Ashford
Spring globulars
After a winter drought, globular clusters hove into view in the spring for Northern Hemisphere
observers. Globular clusters are huge balls of stars, numbering up to a million in some cases. ey
have very old stars, with ages from around 12 billion to 13 billion years, meaning they formed at
about the same time as our Milky Way Galaxy. ey orbit around our Galaxy but not in the galactic
plane, and they lie at various distances, from 7,000 to 400, 000 light years from us.
e rst of the ‘big two’ spring globular clusters that I will be looking out for is the magni cent
Messier 5 in Serpens. Although it does not culminate at a great altitude, it is high enough to get a
really nice view, even with a small telescope. Near to M5 is the challenging globular cluster Palomar
5, at magnitude +11. Low down in the sky at this time of year are the globular clusters of
Ophiuchus, which has more globular clusters than any other constellation, most located near its
boundary with Sagittarius. Some of these clusters, such as M10, M12 and M14, are relatively bright
and easy to spot, but there are also quite a few fainter NGC clusters to track down. You should also
look out for NGC 5897 – the lone globular in Libra.
e second of the ‘big two’, which will be on everyone’s list of targets come the spring, is the ‘Great
Globular Cluster’ of Hercules, M13, which is easy to nd near the Keystone asterism. Also in
Hercules are M92 and NGC 6229, which are both overlooked and underobserved globulars. For a
big challenge, try seeking out Palomar 14, which is a faint (14th-magnitude) and sparse globular
that may be beyond the limits of many observers.
Callum Potter
Opposition of Jupiter – August
I confess, Jupiter has been my favourite planet from the beginning. Saturn comes a close second, but
its smaller disc and fainter pastel hues cannot compete with the bold detail provided by jovian belts
and zones.
I am not primarily an imager – as I often remind my peers, many of whom produce images of
celestial objects that are truly astounding. If I produce a good image, it is more likely by accident
than by design. However, I recently purchased a moderately able CMOS camera with which I have
obtained passable images of Mars. Alas, my acquisition came just a little too late to capture Jupiter,
which by that time was racing into the domain of the setting Sun.
In any case, Jupiter had not been observationally friendly during 2020. Even at opposition, it had
played peek-a-boo with rooftop chimneys at a maximum altitude of just 15 degrees. At this angle, its
re ected sunlight had to travel through almost four times as much agonised swirling atmosphere as
objects visible at the zenith.
But 2021 will be different. During its opposition on 20 August, Jupiter will lift to an altitude of 23
degrees. is may not seem much of an improvement, but atmospherically, its light will be hindered
by one-third less atmosphere than in 2020. is will not only be a signi cant gain in clarity for
visual observers, but will also provide a more stable column of air through which Jupiter’s
photographic image can pass. I will be waiting.
Steve Ringwood
Astronomy Now canvassed its cadre of expert writers to nd out what they were most
looking forward to from an amateur astronomy perspective over the next twelve months.
Hopefully 2021 will see the return of star parties – tents, red lights, and clear skies!
Look for the Perseids in a Moon-less night about 30 degrees from Perseus.
Large binoculars or a telescope of at least 100mm aperture should show comet 67P moving through the winter sky.
The ash of a lunar impact.
The Moon will bite a chunk out of the Sun on 10 June.
The Squid Nebula, imaged with a CMOS camera in just a couple of hours.
The track of the occultation of the star HIP 12148 by a Jupiter Trojan asteroid.
Hercules’ Great Globular Cluster, M13.
Jupiter and its moons will climb higher in 2021.
ViewWhat to look forward to in 2021
January 2021
Astronomy Now