by Anne Holt Sunrise 1st: 04.44 31st: 05.22 Sunset 1st: 21.40 31st: 21.07 Astronomical darkness: none until 31st, then 00.54 to 01.36 Astronomical twilight 1st: 00.05 to 02.20 increasing by a few minutes each day to 3.5 hours on 30th. New Moon: 2nd July at 20.16 Full Moon: 16th July at 22.38 The
July full Moon is known as the Buck Moon, because this is the time when
new antlers start to grow on the head of the deer. Other names are the
Thunder Moon and the Anglo Saxon Hay Moon or Wort Moon. Lunar Perigee: 5th at 04.56 (363727 km) Lunar Apogee: 21st at 00.02 (405478 km) Earth is at aphelion on 4th at 03.11, when it will be 152 million km (1.02 AU) from the Sun. Highlights We
have a partial Lunar eclipse on 16th. However, like nearly everything
else at the moment, it will be very low in the sky. When the Moon rises
at 21.25 it will already be partly in shadow. The maximum of 65% is at
22.30, when the Moon will still be only 5.9 degrees above the horizon.
The umbra leaves the face of the Moon at 23.59, when it is at an
altitude of 12 degrees. As if that wasn't bad enough, statistically
this evening has an 82% chance of being cloudy. There's a
total Solar eclipse on 2nd. This one starts over British territory,
unfortunately it's not somewhere close to here - it's Oeno Island in the
South Pacific. The path of totality then moves over the ocean to La
Serena in Chile, over the Andes and into Argentina, ending to the south
of Buenos Aires. Closer to home, Jupiter is still
shining brightly, unmissable despite being so low in the sky, Saturn
reaches opposition so the rings will appear extra bright for a few days,
but again very low. For binocular and telescopic observing the
positions of Uranus and Neptune are both improving. They are much
higher than the naked eye planets. We are still in the
noctilucent cloud season. These normally occur a couple of hours before sunrise in the NE and after sunset in the NW, but recent displays have
been more widespread. And, of course, we have the 50th
anniversary of the Apollo 11 mission - the Giant Leap for Mankind.
The Eagle landed at 21.18 BST on July 20th 1969. The Moon doesn't
rise until 23.17 on this day, so we can't look up at it at the exact
moment. Neil Armstrong first stepped on to the Moon's surface on 21st
at 03.56, followed at 04.15 by Buzz Aldrin. The waning gibbous Moon
sets at 09.44 on this morning, so will be above the horizon at the exact
time of the anniversary. Constellations Planets Mercury: in Cancer, mag 1.0 Not
easy to see this month. On 1st it sets at 22.43, about an hour after
the Sun, but is just below the horizon by the time the sky begins to
darken. On 3rd it is only 3.8 degrees from Mars with the thin crescent
Moon also close. The Moon sets 45 minutes after the Sun, with the
planets following soon after. On 7th it is at aphelion, the furthest
point in its orbit from the Sun, at a distance of 0.47AU (about 70
million km). On 21st it reaches inferior conjunction, passing between
the Earth and the Sun, but because of the inclination of its orbit to
the ecliptic this rarely results in a transit. This time the planet
passes about 5 degrees south of the Sun. Mercury moves into Gemini on
23rd but is still too near the Sun to be visible. On 31st it rises at
04.29 nearly an hour before the Sun but is separated from it by only 14
degrees. On this day the 1% Moon passes 4 degrees to the north but they
are only 2 degrees above the horizon when the sky brightens. Venus: in Taurus, mag -3.9 On 1st it rises at 03.49 but
only reaches 1 degree above the horizon by dawn. It moves into Gemini on
4th and into Cancer on 27th. By 31st it rises 30 minutes before the
Sun and appears separated from it by only 4 degrees. Mars: in Cancer, mag 1.8 Still
an evening object but now very difficult to see as it sets before the
sky gets really dark. On 1st it sets at 22.52, about 70 minutes after
sunset and has sunk below the horizon by dusk. It moves into Leo on
31st, when it sets only a few minutes after the Sun and appears only 10
degrees from it. Jupiter: in Ophiuchus, mag -2.6 Still
very bright in the southern sky. On 1st it culminates at 23.33, at 14
degrees above the southern horizon. On 13th the 90% lit Moon passes
less than 3 degrees north of the planet. The pair should be visible, 13
degrees above the horizon, at around 22.00. On 31st it culminates at
21.25, as the sky darkens, setting at 01.20 and will have faded slightly
to mag -2.4. Saturn: in Sagittarius, mag 0.1 Now
at its best for the year but still very low and, unlike Jupiter, not
bright enough to really stand out at that altitude. On 1st it
culminates at 01.50, only 14 degrees above the southern horizon, setting
at 05.42. It's at opposition on 9th, when it reaches its highest
point, still only 14 degrees, at 01.16. For a few days around this time
the rings appear much brighter than usual because of the sunlight
falling directly on them at this time. Firstly, the shadows of the
particles comprising the rings fall directly behind and can't be seen,
rather than being visible to the side and having a dimming effect. Also
sunlight is reflected directly back, which again makes the rings appear
brighter. The full Moon passes only 13 arcminutes from the planet on
16th at 08.16, in daylight. It will appear to the west of the planet on
the night of 15/16th and to the east on 16/17th. On 31st Saturn
culminates at 23.38, now marginally fainter at mag 0.2, setting at
03.32. Uranus: in Aries, mag 5.8 Not
easy to see in early July. On 1st it rises at 01.30 but is barely
above the horizon by the time the sky starts to brighten. Its position
improves during the month and in the second half it should be high
enough in the still dark sky to be a reasonable binocular target, maybe
even a naked eye object from a dark sky site. On 15th it reaches 15
degrees in the east while the sky is still reasonably dark and on 22nd
will be at 22 degrees by dawn. On 25th the third quarter Moon passes
about 6 degrees south of the planet. By 31st it rises at 23.29 and is
at 31 degrees in the SE when the sky begins to brighten. Neptune: in Aquarius, 7.8 Another
morning object, quite low in the first half of July but then should be
high enough in the early hours to be seen in amateur scopes. On 1st it
rises at 00.18 and reaches 10 degrees by dawn. Like Uranus its position
improves during the month, by 15th it is at 22 degrees in the SE when the
sky begins to brighten. On 21st the waning gibbous Moon passes about 6
degrees south of the planet at 2am. On 31st it rises at 22.16 and gets
to 30 degrees in the south in darkness. Dwarf Planets Of
the 5 officially designated dwarf planets only Ceres, orbiting in the
Asteroid Belt, is close enough and bright enough to be within range of
amateur scopes - and even that is so small that, despite having a
magnitude similar to Neptune, it will never appear as anything other
than a point of light. The others, orbiting way out in the Kuiper Belt
are very faint but can sometimes be possible targets for experienced astrophotographers using the comparison
method, similar to the way Pluto was found by Clyde Tombaugh in 1930. Ceres: in Libra, mag 7.8 On
1st it culminates at 22.28 at 17 degrees in the south, setting at
02.07. By month end it will have faded to mag 8.4, culminating before
the sky gets dark and setting at 00.36. Pluto: in Sagittarius, mag 14.6 Still
too low to be successfully imaged this month despite reaching opposition
on 14th, when it will be 14 degrees above the southern horizon at
01.16. Haumea in Bootes, mag 17.4, and Makemake
in Coma Berenices, mag 17.2 are both reasonably high in the sky in
early July but losing altitude during the month. Haumea reaches 31
degrees in the west by dawn on 1st and 28 degrees on 31st. Haumea is
slightly lower at 26 degrees and 23 degrees. Eris: in Cetus, mag 18.8 The
most distant of the dwarf planets has a very eccentric orbit, almost
twice as far from the Sun as Pluto at aphelion, taking 558 years to
complete one orbit. It is very low in the sky for most of July but by
month end it might be a reasonable photographic target at around 03.15,
when it will reach 22 degrees before the sky begins to brighten. Comets 46P/Wirtanen amd 38P/Stephan-Oterma are now too faint and too low to be seen. However,
there are 4 which are quite promising, all still below the horizon at
dawn in early July but improving position and brightening as the month
progresses. C/2017T2 (PANSTARRS) in Taurus, mag 10.8 Should
be high enough to be seen in a decent scope by the end of the month. On
31st it should be at mag 10.1, rising at 01.32 and reaching 13 degrees
before the sky brightens. C/2018N2 (ASSASSN) in Cetus, mag 11.8 Moves
into Aries on 12th, when it is still only 6 degrees above the eastern
horizon by dawn. By 31st it should have brightened to mag 11.4 and will
reach 29 degrees before the sky gets too light for it to be seen. 168P1/Hergenrother in Pisces, mag 12.2 Briefly
visits Cetus on 9th, then moves into Aries on 10th, when it will be
only 8 degrees in the east by dawn. By 31st it should have brightened
to mag 11.8 and be at 31 degrees in the east in reasonable darkness. 260P/McNaught in Cetus, mag 13.2 Should
reach 12 degrees by daybreak on 12th, when it is predicted to be at mag
12.8. By 31st it should have brightened to mag 12.1 and get to 29
degrees in the SE before the sky begins to brighten at around 03.15. For more information and exact positions of all Solar System objects see; and for currently visible comets Meteor Showers We have a few minor showers, especially towards the end of the month Alpha
Capricornids: active July 3rd to August 15th have a plateau-like peak
centred on 30th, ZHR 5 but with a strong possibility of several bright
fireballs. Parent comet 169P/NEAT. Southern
Delta Aquarids: July 12th to August 23rd, peak 29/30th, ZHR 16 - from
the southern hemisphere, far fewer here. These medium paced meteors are
debris from comet 96P/Machholz. Piscids
Austrinids: July 15th to August 10th peak 28th, ZHR 5. Again the
radiant is very low from our latitude, the shower is much better seen
from further south. The antihelion source,
meteors not belonging to any particular shower, having a radiant on the
ecliptic opposite the position of the Sun, is active in July, ZHR 2 to
3. Meteors from this should be distinguishable from the named showers
above, despite the radiants being quite close together, as those from
the ANT are much faster moving. |
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