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Telescope House April Sky Guide


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

The Solar System 


The Moon


The Moon begins April as a Waning Crescent on the Aquarius/Capricornus borders, sitting a little to the west of Venus - the two forming a pretty pairing in the dawn sky. 


New Moon occurs on the morning of the 5th, when the Moon passes to the south of the Sun on the Cetus/Pisces borders. This is the best part of the month for deep sky observers and imagers, with Moonlight not around to interfere with observations or exposures. 


From this point the Moon enters the evening sky and over the next week displays one of the highest Waxing Crescent phases of the year for northern hemisphere observers. This is one of the Moon’s “High Spring Crescents” and presenters observers and imagers in the northern hemisphere with a great opportunity to see the Moon at its best in the evening skies. 


The Moon shoots up the ecliptic through Cetus, Aries, Taurus until it reaches its most northerly Waxing Half Moon phase of the year in Gemini, on the evening of the 12th. 


The Moon at sunset, 14th April, having reached most northerly Half Phase of the year.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


On the following evening, the Moon will graze the southern edge of M44, the Beehive Cluster (Praesepe) in Cancer. 


The Moon reaches Full on the 19th, while in Virgo, making this time of the month the most awkward for those engaging in deep sky observation or astrophotography. 


Last Quarter occurs on the 26th April, while the Moon is riding low in the sky for northern hemisphere observers in Sagittarius. April ends with the Moon a Waning Crescent in Aquarius, some 17% illuminated, sitting just a little to the south of Neptune in the same constellation. 






Mercury begins April as a morning object.  At just under 24 degrees from the Sun, it is only just over 5 degrees in elevation (from 51 degrees N) at sunrise.  This, coupled with a relatively narrow crescent phase of 23%, means the planet’s brightness is comparatively low, at +1 mag, which will make picking it out in the dawn sky a very tricky task from mid-northern latitudes (though those in the equatorial regions and souther hemisphere will fare a little better).  The much brighter Venus, 10 degrees to the west of Mercury, will provide something of a rough signpost to the much fainter planet’s location, but in truth, there are easier and more rewarding targets for those in mid-northern latitudes to turn their attentions to at this time.


Mercury reaches maximum western elongation from the Sun on the 11th, but although brightening slightly to +0.4 mag, is actually sinking in terms of angular separation from the horizon, making it even more difficult to observe.  By mid-month, Mercury and Venus have drawn closer together in the sky, making the part of heavens that Mercury is located in more apparent, but the angular separation of both targets from the horizon in mid-northern latitudes remains poor.  The two planets appear to “fly in formation” alongside each other in conjunction for the rest of the month at a separation of under 5 degrees, but again, location in the sky means you will have to have a very clear horizon and clement atmospheric conditions to see much of this at all, in this part of the world.  Though again, those in the equatorial regions and southern hemisphere will fare a little better in this respect.


Mercury and Venus in Conjunction, sunrise, 14th April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,




As previously mentioned, Venus is a morning object and found alongside Mercury and the Old Crescent Moon in Aquarius at the beginning of April.  Separated from the Sun (on the western morning side) by a little over 34 degrees, at mag -4.0 and 82% illuminated, it is a brilliant target and unmistakable in the low easterly sky, having reached an altitude of 7 1/2 degrees at sunrise (from 51 degrees N).  Being so low, magnified views will be negatively affected by seeing conditions, but aperture and filtration (particularly a Deep Red No. 29 Filter), can be used with a telescope to try and improve the view somewhat (as long as your telescope’s of reasonable aperture).


Venus, alongside the Moon and Mercury, sunrise, 1st April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


By mid-month, the planet has dropped fractionally in both brightness (now mag -3.9) and altitude (sitting at a little over 6 degrees high as the Sun rises).  As touched upon above, Mercury will be “flying in formation” alongside its much more brilliant neighbour during this period and Venus will act as a useful beacon to its location, though bright morning skies, the turbulent atmospherics of this elevation in the sky will make this a very tricky task.


By the end of the month, nothing’s changed dramatically as far as Venus is concerned: the planet’s still -3.9 mag brightness and just below 6 degrees in elevation at sunrise.  It can be now found 28 degrees to the west of the Sun.





The Red Planet is a resident of Taurus and can be found in-between the Pleiades and the Hyades at the beginning of April.  At +1.5 mag and a meagre 4.6 arc seconds diameter, it won’t be the best planetary target to seek out this month, due to its very small angular size.  Despite Mars’ great position in the sky for those of us in the northern hemisphere, its going to be the latter half of 2020 before we can really enjoy it telescopically again from a visual point of view.  This is not to say that there’s nothing to see on Mars’ surface at all at higher magnifications, just that those with smaller telescopes should ready themselves to not see a huge amount. Experienced imagers with larger telescopes will be able to pull out some reasonable detail still, using higher speed filming and stacking techniques, though this will require patience and a reasonable level of equipment.


By the 15th, Mars will have drawn almost due north in the sky of Aldebaran, Alpha Tauri, the two separated by about 6 1/2 degrees.  Although around half a magnitude fainter than Aldebaran, it will be interesting to compare the colour of the two targets, which often appear pretty similar from a colour temperature point of view (the star is undoubtedly the hotter, temperature-wise, of the two though!).


Mars' path through Taurus, April 2019.  Position of Mars shown, 1st April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


By the end of April, Mars has faded a little to +1.6 mag and shrunk somewhat to 4.2 arc seconds diameter. On the 30th it can be found between the two “horns” of Taurus, gently tracking up to the highest part of the northerly ecliptic, which is will reach in May.





Resident of the non-Zodiacal constellation of Ophiuchus, Jupiter is a fine morning object at -2.2 mag and is around 40 arc seconds diameter at the beginning of the month.  Although not in an absolutely ideal location for those of us in the northern hemisphere, the planet reaches an elevation of over 16 degrees above the horizon at transit point in the south, which it reaches at a little before 6am on April 1st.


By mid-month the planet has brightened fractionally to -2.3 mag and increased its diameter to 41.6 arc seconds.  Rising at just after 1am, Jupiter will transit at a little after 5am - so is most definitely a target that will reward the early riser.


Jupiter dual GRS and Ganymede Transit, predawn, April 23rd.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


By the month’s conclusion, Jupiter has increased magnitude to -2.4 and is now 43.4 arc seconds across.  Transiting at a little after 4am, it will rise now at just past midnight.  By the 30th, Jupiter is under 6 weeks from opposition in early June, so now’s the time to get up early and make the most of the King of the Planets.





Always a more sedate and less brilliant target than its neighbour Jupiter, Saturn continues to chug slowly through Sagittarius.  Reaching a similar altitude above the horizon to Jupiter at transit point, Saturn is considerably fainter at +0.6 mag and displays a disk of 16.4 arc seconds on the 1st.  Saturn rises a little before 4am and transits at a little after a quarter to 7 in the morning.


As with most things Saturnian, nothing changes rapidly.  By the 15th, the planet has brightened to +0.5 mag and is now 16.7 arc seconds diameter.  Saturn finds itself flanked by the Waning Gibbous Moon on the mornings of the 25th and 26th April, the two bodies separated by about 5 degrees to the west and the east on successive mornings.


By the time April has drawn to a close, Saturn finds itself standing just shy of transit in the south as the Sun rises, reaching an altitude above the horizon of 17.22 degrees (from 51 degrees N).  The planet now displays a disk of 17,2 arc seconds diameter, though still at +0.5 won’t appear any brighter than it did at the month’s beginning.


 Saturn and Inner Moons, 30th April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,



Uranus and Neptune


Both the Outer Gas Giants are very close to the Sun as the month begins.  Uranus is at Superior Conjunction on the 23rd, so is to all intents and purposes unobservable. 

Uranus at Superior Conjunction, 23rd April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Neptune re-emerging as a morning object after its own Superior Conjunction in early March, is still a too close to the Sun for meaningful observations as yet.  Neptune has a very close conjunction with Venus on the morning of the 10th April, with the two separated by just 17 1/2 arc minutes.  Unfortunately, proximity to both horizon and Sun will mean that while Venus will (though very low) be relatively straightforward to spot (if skies and horizons are clear).   Neptune, at +8.0 mag will not be visible, drowned out it the glare of the dawn sky. 




Comet 2018 Y1 (Iwamoto) peaked in brightness as it passed us in February and early March but has now faded.  The comets has been slowing in its apparent angular westerly momentum and in mid-April performs a hairpin bend in the sky in Perseus and begins to head east.  By this point the comet will be faint and certainly out of the reach of all but the largest of binoculars under the darkest of skies.  While it will still be possible to observe and image the comet with telescopes, despite its relatively favourable location in the sky from a northern hemisphere perspective, it will be a real test of observing skill and patience.


Comet Iwamoto's path and change of direction, April 2019.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


We have the upcoming C/2017 T2 (Panstarrs) to look forward to in the latter half of the year, which may make binocular brightness in terms of observability.  This comet will be very well placed for northern hemisphere observers in the Autumn, but at current time is still very faint.





The Lyrid Meteor shower peaks on the night of the 22nd-23rd April.  Fed by the periodic Comet 1861 G1 (Thatcher), this shower is not strong in numbers, peaking at a Zenithal Hourly Rate of around 15-18 meteors.  To compound this, the nearly 88% illuminated Gibbous Moon will be sitting due south of the radiant all night, spoiling the potential of this year’s showing.  Although meteors can appear in any part of the sky, with their source tracing back to the radiant, Moonlight will drown out all but the brightest.  There will be other showers this year which will deliver a better experience than this one.



Deep Sky Delights in Canes Venatici


Although a faint an uninspiring constellation from a naked eye perspective, Canes Venatici, the Hunting Dogs, sitting just under the “handle” of the Plough or Big Dipper asterism of Ursa Major, is home to some of the most glorious objects in the sky.  It is galaxy-rich, as many of the constellations around it are.


The first and best-known of all these is the remarkable M51 - the Whirlpool Galaxy.  The Whirlpool is possibly the archetypal face-on spiral galaxy.  Whereas M101 is large and relatively faint, M51 at +8.39 mag and 11.2 x 6.9 arc minutes area is more compact and brighter.  This galaxy has two massive spiral arms, bound around one another.  On the tip of the northern arm, is a companion galaxy, NGC5195, which is in the process of heavy tidal interaction with M51.


M51. Image Credit: Mark Blundell

M51 is a true Messier object - it was discovered by him in 1773, though Pierre Mechain discovered NGC5195 later in 1781.  Lord Rosse made a famous sketch of M51 through is 72 inch reflector in 1845, which clearly showed M51's Spiral and its satellite - it is this sketch that gave rise to the nickname "Rosse's Question Mark" - for obvious reasons.  


Although M51 can be found relatively easily in binoculars, a dark sky will be needed to active this.  Small telescopes will show M51's core easily and the first suggestion of a halo surrounding this.  However, once the 12-inch barrier is broken in terms of aperture, then M51, really begins to come into its own.  This aperture and above will show the Whirlpool in all its glory - and notable features such as the bridge between M51 and NGC5195 and M51's numerous H II regions really begin to stand out.  However, it is in long duration images that M51 really reveals all - and in this respect is a constant source of inspiration to astrophotographers.


M51 is thought to be of a similar size to both our galaxy and M31, the Andromeda Galaxy, and lies around 27 million light years away.  


Just under 40 arc minutes to the S of M51 lies the elliptical galaxy NGC5173, otherwise known as the Southern Integral Sign.  Although +12.19 mag in brightness, it is relatively compact at just 1 x 0.9 arc minutes dimensions and is thus quite evident in small telescopes, though rather disappointingly bland in relation to the many spirals that surround it.


Just under 6 degrees to the south of M51 lies the lovely M63, the Sunflower Galaxy.  This is a truly beautiful object - a tightly packed spiral with a bright core and fainter outlying arms.  It certainly does look distinctly flower-like in long duration images.


The Sunflower has the distinction of being the first discovery made by Pierre Mechain - Charles Messier's partner and major contributor to his list.  At +8.6 mag and 12.6 x 7.2 arc minutes across, M63 makes for a relatively straightforward target in most small telescopes, though larger instruments will be needed to make out the spiral structure.  This was first noted by Lord Rosse during his survey of spiral nebulae during the 1840s.  


M63. Image Credit: Mark Blundell


M63 is thought to lie around 34 million light years from us and is part of the group of galaxies in this area of sky of which M51 is the dominant gravitational member. 


4 and 3/4 degrees to the W of M63, we find the distinct galaxy M94, which was another discovery of Mechain in 1781 - and was added to the Messier list in the same year.  M94 is, like its major neighbours, a spiral galaxy - albeit a rather unusual one.  At +8.19 mag and 14.1 x 12.1 arc minutes area, M94 lies about half the distance from us - 14 million light years - than either M51 and M63.  Its structure is notable - a tight compact, very bright spiral core, surrounded by two concentric fainter rings of stars.  It is due to this structure that it has gained the nickname in some circles of the Cat's Eye Galaxy.  This suggestion of spiral structure shows up well in even small telescopes, though instruments of 8-inches aperture + are needed in order to see much of the outer rings.  M94 can be found in binoculars, if sky conditions are kind  though a telescope is definitely needed to see anything more than a faint smudge.  When imaged, M94 gives up considerable detail, especially in its outer ring.


The beautiful core of M94, as imaged by the Huble Space Telescope.  Image Credit: NASA/ESA, Public Domain/Creative Commons


Just over 5 1/2 degrees further S from M93 lies NGC5005 - yet another spiral galaxy.  At +9.80 mag and 5.8 x 2.9 arc seconds area, this object has a really bright nucleus, surrounded by a much darker, almost sooty-looking outer arms.  In larger telescopes, the elongated aspect of NGC5005 really begins to revel itself, though in truth, this galaxy is a rather disappointing object in smaller instruments and binoculars.


Under 7 1/2 degrees to the SW of NGC5005, sits the slightly easier to observe NGC4631, otherwise known as the Whale Galaxy.  This +9.19 edge-on spiral galaxy does indeed resemble a galactic whale swimming through the cosmos.  At 15.2 arc minutes long by just 2.8 arc minutes wide, the Whale has quite high surface brightness and is therefore a relatively easy object in most large binoculars and small telescopes.  A companion galaxy, NGC4657, sits to the N of the Whale and is thought to be responsible for some of the larger galaxy's elongation.  Both objects lie around 25 million light  years away and were discovered by Sir William Herschel in 1787.  To the SE of the Whale, by around half a degree, sits another spiral galaxy, NGC 4656, otherwise known as the Hockey Stick.  Photographic evidence reveals why, as one edge of NGC4656 appears bent - just like a hockey stick.  Just like NGC4631, the Hockey Stick was discovered by Herschel, though lies a little further from us than its neighbour, at 30 million light years away.

The Whale and Hockey Stick Galaxies, NGCs 4631 and 4656.  Image Credit: Mark Blundell


Under 8 degrees to the NW of the Whale, lies the superficially very similar NGC4244 - the Silver Needle Galaxy.  This is another spiral which lies edge-on to our perspective and although a little fainter at +10.6 mag than its neighbour is well worth seeking out.  At 16.6 x 1.9 arc minutes in area, the Silver Needle has a somewhat lower surface brightness that the Whale, but is impressive enough in larger telescopes.  Although difficult to see from our point of view, NGC4244 is thought to be a barred spiral structure with two wide arms. Sources differ as to the distance this galaxy lies from us, with most seeming to favour the 14 million light years mark, though some putting it as close as 6.5 million light years away. If the latter is closer to the truth, NGC4244 is possibly an outer member of our own local group rather than a galaxy belonging to the Canes Venatici family.


NGC4244, Hubble Space Telescope.  Image Credit: NASA/ESA, Public Domain/Creative Commons


4 1/2 degrees to the NE of NGC4244 sits two interaction galaxies, NGCs 4485 and 4490 - otherwise known as the Cocoon.  These 6.4 x 3.2 arc minute objects have a cumulative magnitude of +9.80 and have undergone a catastrophic interaction with each other - much as the Milky Way and M31 are thought to experience in the far future.  Although both galaxies are now moving away from each other, there are some remnants of spiral structure left in a massive arc of stars and material stretching 24000 light years in length between both objects.  This seemingly destructive interaction, as it often does, has sparked a huge amount of star formation in this region.  Both galaxies - or what's left of them - are thought to lie some 31-50 million light years away from us.


The Cocoon Galaxies.  Image Credit: Joel Schulman, Creative Commons


2 1/2 degrees to the N of the Cocoon, sits NGC4449.  This galaxy is something of a rarity in this part of the sky, being of an irregular, rather than a spiral structure.

 NGC4449 was discovered by Sir William Herschel in 1788 and is +9.6 mag in brightness and 6.4 x 4.4 arc minutes in size.  NGC4449 is superficially very similar to the larger of our two satellite galaxies, the Large Magellanic Cloud, though observations of this diminutive galaxies in radio wavelengths have revealed that the visible part of NGC4449 is dwarfed by a huge, optically invisible halo of gas, which is 14 times its diameter.  NGC4449 is easily enough found in larger telescopes, and the mottling of its HII regions is impressive if enough aperture is directed its way - though admittedly this galaxy does lack some of the glamour of its neighbours.


NGC4449, Hubble Space Telescope. Image Credit: NASA/ESA, Public Domain/Creative Commons


Just over 3 1/2 degree to the N of NGC4449, lies the last galaxy in our epic jaunt around this area of sky - M106.  This +8.39 mag spiral galaxy was discovered by Mechain in 1781, but was not added to the catalogue by Messier at the time.  M106 is, like some previously mentioned galaxies, a later, 20th century addition to the original list.  M106 is a fine galaxy - well presented from our perspective and bright enough to be seen in diminutive telescopes.  However, a 12-inch + class of telescope will really start to reveal the two massive bound spiral structure of the arms and the darker material that lies between.  At 18.6 x 7.2 arc minutes, M106 is a healthy size for a galaxy - larger than M51 and as such, should probably get a little more attention than often does.

 M106 and attendant galaxies.  Image Credit: Mark Blundell


The last object in this remarkable constellation isn’t a galaxy, but one of the best globular clusters in the sky, M3.  M3 was discovered by Charles Messier in 1764 and as its catalogue number suggests is one of the first objects he recorded in his list of “fixed” objects that could be misidentified as comets.  M3, at +6.19 mag is one of the brightest Globulars in the northern hemisphere of the sky - bested in brightness only by the superlative M13 in Hercules and M5 in Serpens.  M3 can be seen by the keen-eyed under good conditions with the naked eye, but it is in binoculars and telescopes that it really reveals its true beauty.  With binoculars, it is easily seen as a fuzzy ball of delicate light.  A 3 or 4 inch refractor will resolve some stars on the outer edge and will definitely show signs of granular structure.  An 8-inch+ reflector will resolve individual stars in M3’s core - which was first achieved by none other than William Herschel, who counted it as one of his favourite objects to observe.  Tracing a line up from Arcturus, Alpha Aurigae in neighbouring Auriga to Cor Caroli, Alpha Canes Venaticorum, will reveal M3 round 2/5ths of the way between the stars.  At just under 34,000 light years away, M3 is home to around half a million stars.  The cluster is thought to be around 8 billion years old. 


  M3.  Image Credit: Mark Blundell

Text: Kerin Smith