At first the Sun lies within the constellation of Gemini, until, on the 20th at 23h00, it crosses the
border into neighbouring Cancer. A significant date is that of the Earth’s Aphelion - July 6th, when at 16h15, the
Earth is the furthest distance that our planet can be from the Sun, 152 103 776 km (1.016750939 au) (centre to centre). AU is the symbol for an astronomical unit; which is the mean (average) distance between the Earth and the Sun.
As in June, twilight persists all night, and the season for observing Noctilucent Clouds continues. Look towards the northern sky during the two hours centred on astronomical midnight for these ethereal silvery veils
in the northern sky.
Moon is at Apogee,
its furthest point from the Earth, on the 13th July at about 08h00. The angular diameter of the Moon is 29’ 56” of arc. Perigee, when the Moon is at its nearest to Earth, is on the 27th at 05h. The angular
diameter then is 33' 05”
Last Quarter Moon, in Cetus, is on the 6th, at 07h51
New Moon in July is on the 13th at 02h49, when it lies in the constellation of Gemini, passing 2° to the south of the Sun. There
is a minor partial eclipse of the Sun visible in the southern hemisphere between Australia and Antarctica.
is on the 19th, at 19h53, when the Moon is in the constellation of Virgo. The star 6° to the lower right of the Moon is Spica (alpha Virginis, brightest star in Virgo)
Full Moon is on the 27th at 20h21 in the constellation of Capricornus and in conjunction with Mars, which is at its brightest and at Opposition. Mars lies 5° south of the Moon
at the time. The Moon rises at 20h03 (21h03 BST) already in total eclipse mode; which starts at 17h51 when Luna enters Earth’s penumbral (or ‘partial’) shadow. The Moon begins to leave the umbra ( ‘full’ shadow) at 21h13.
The Moon’s entire surface is out of the umbral shadow at 22h19. At 23h28, the Moon has left the Earth’s shadow completely.
At the beginning of the month, Mercury sets 90 minutes after the Sun, but this interval
decreases as the planet moves in towards the Sun for its Inferior Conjunction on August 9th. The best time to see Mercury, and it is best located using binoculars, is during the first week of the month, when the planet may be found in the twilight
of the WNW sky at around 21h. At this time the planet is just less than 10° above the horizon. Do not confuse Mercury with the much brighter Venus, which lies at an altitude of 11°, some 16° to the left of Mercury. Mercury is at its greatest eastern
elongation (26°) east of the Sun on the 12th.
The waxing crescent Moon may be seen approaching Venus on the evening of the 15th.
and lying to the east of the planet, the next day. Venus continues to shine brightly, in the Summer twilight as the 'Evening Star', 'Hesperus'.
Mars is at Opposition on July 27th and in conjunction with the eclipsed Full Moon on that day. It shines at magnitude -2,8 ( brighter than
Jupiter!)and has a disc of 24.3 seconds of arc. The planet reaches its nearest to the Earth several days later on the 31st. Mars is a conspicuous object all night long, albeit low in the southern sky when it culminates, (crosses the south meridian)
at astronomical midnight.
Jupiter in the constellation of Libra is a bright and beautiful object as evening twilight
fades at around 21h. It may be seen some 18° above the SSW horizon shining steadily and brightly at magnitude -2.2. The waxing gibbous Moon may be seen approaching Jupiter on the 20th, when at 21h, the planet lies 4° to the lower left of
Remember to look at the 'nightly dance' of the Jovian satellites through well-focussed and firmly fixed binoculars. On the front page of these Sky Notes, the daily configuration of the four
Galilean satellites is shown for late evening.
Saturn continues to be visible for most of the night; opposition having
taken place at the end of last month. It lies in the constellation of Sagittarius just to the south of the fourth magnitude star nu Sagittarii, (with the proper name Polis). The waxing gibbous Moon may be seen approaching Saturn during the evening of the 24th
and at 23h lies just over 3° to the right of Saturn. Saturn’s largest moon Titan lies at its greatest elongation east of the planet on the 1st and 17th, and greatest western elongation on the 8th and 24th.
Titan has a magnitude of +8.2, slightly fainter than the planet Neptune +7.8.
On the first of July, Uranus rises shortly
after 00h00, and is rising just after 22h as the month ends. It lies in the constellation of Aries and is currently at magnitude +5.8, and is on the threshold of naked eye visibility. The nearest comparable star in brightness is HR 578 Arietis at visual magnitude
+6.09, which lies 41 minutes of arc to the NW of Uranus. See the Remote Planets page of these Sky Notes, accessible via the Menu, for a chart plotting the path of Uranus during 2018.
During July Neptune rises at around 22h and lies just over 1° to the west of the +4.22 magnitude star phi Aquarii in the eastern part of the constellation of Aquarius. This remote world is
faint at m(v) +7.85 and requires a telescope of reasonable magnification to positively identify its tiny disc. During the last week of the month at astronomical midnight, the planet may be seen at an altitude of 25° in the SE sky below the ‘Great
Square’ of Pegasus, the stars Scheat (beta Pegasi) and Markab (alpha Pegasi) pointing down towards it. (See Remote Planets page as before)
Dwarf planet Pluto is at Opposition, and its nearest to the Earth, on the 12th in the constellation of Sagittarius. The visual magnitude of this remote world
is +14.2. Pluto lies 12 minutes of arc to the west of the +5.59 magnitude star 50 Sagittarii. The path of Pluto can be found on the Remote Planets page.
Two minor meteor showers take place at the end of the month. One is the Capricornids, which are active during July and August. Three peaks are recorded for this shower
– July 9th, 16th, and 26th.
Twilight may interfere. You may, however, be lucky and see 5 alpha Capricornids in the space of one hour.
On the 29th, and again on August 6th,we have the maximum of the delta Aquarids, with up to 20 an hour, although these
meteors tend to be faint.
Towards the end of July, the Perseid Meteor Shower begins, and starts to build towards its maximum on August 13th at 01h.
Constellations visible in the south around midnight, mid-month, are as follows: Sagittarius, Sagitta, Aquila, Lyra and Cygnus. The latter constellations contain Patrick Moore’s
‘Summer Triangle’, consisting of the three bright stars, Altair in Aquila, Vega in Lyra, and Deneb in Cygnus. Cygnus is sometimes called the ‘northern cross’ because of the cruciform shape of its five main stars.
All times are GMT 1° is one finger width at arm’s length.
The phenomena of the month : JULY 2018
Times are given in UT for SCARBOROUGH (0° 25' 5" W, 54° 16' 30" N, zone 0 UT).
Date Hour Description of the phenomenon
yyyy mm dd hh:mm
2018 07 01 05:20 Minimum of the variable star Algol (beta Persei)
2018 07 02 01:29 Beginning of occultation of 40-gamma Cap, Nashira, (magn. = 3.69)
2018 07 02 01:51 End of occultation of 40-gamma Cap, Nashira, (magn. = 3.69)
2018 07 02 23:53 Maximum of the variable star delta Cephei
2018 07 04 00:35 Maximum of the variable star eta Aquilae
2018 07 04 02:09 Minimum of the variable star
Algol (beta Persei)
2018 07 04 02:29 Close encounter between the Moon and Neptune (topocentric dist. centre to centre = 3.3°)
2018 07 04 09:52 Close encounter between
Mercury and M 44 (topocentric dist. centre to centre = 0.6°)
2018 07 06 07:51 LAST QUARTER OF THE MOON
2018 07 06 17:00 The Earth at its aphelion (distance to the Sun
= 1.01670 AU)
2018 07 06 22:58 Minimum of the variable star Algol (beta Persei)
2018 07 08 02:37 Minimum of the variable star beta Lyrae
2018 07 08 08:41 Maximum of the variable star delta Cephei
2018 07 09 19:47 Minimum of the variable star Algol (beta Persei)
2018 07 10 02:11 Beginning of occultation
of 54-gamma Tau (magn. = 3.65)
2018 07 10 02:27 End of occultation of 54-gamma Tau (magn. = 3.65)
2018 07 10 04:59 Close encounter between Venus and Regulus (topocentric
dist. centre to centre = 1.0°)
2018 07 10 12:01 Maximum of the variable star zeta Gemini
2018 07 11 04:50 Maximum of the variable star eta Aquilae
2018 07 12 06:00 GREATEST EASTERN ELONGATION of Mercury (26.4°)
2018 07 12 10:02 OPPOSITION of Pluto with the Sun
2018 07 12 16:35 Minimum of the variable star
Algol (beta Persei)
2018 07 13 02:48 NEW MOON (partial eclipse of the Sun not visible in SCARBOROUGH)
2018 07 13 08:28 Moon at perigee (geocentric dist. = 357431 km)
2018 07 13 17:28 Maximum of the variable star delta Cephei
2018 07 15 13:24 Minimum of the variable star Algol (beta Persei)
2018 07 18 09:04
Maximum of the variable star eta Aquilae
2018 07 18 10:13 Minimum of the variable star Algol (beta Persei)
2018 07 19 02:15 Maximum of the variable star delta Cephei
2018 07 19 03:30 Comet C/2017 T3 ATLAS at its perihelion (dist. to the Sun = 0.825 AU; magn. = 9.9)
2018 07 19 19:52 FIRST QUARTER OF THE MOON
07 20 10:00 Mercury at its aphelion (distance to the Sun = 0.46670 AU)
2018 07 20 10:13 Opposition of the asteroid 88 Thisbe with the Sun (dist. to the Sun = 2.333 AU; magn. = 9.7)
2018 07 20 15:37 Maximum of the variable star zeta Gemini
2018 07 21 01:12 Minimum of the variable star beta Lyrae
2018 07 21 07:01 Minimum of the variable star Algol
2018 07 24 01:05 Opposition of the asteroid 14 Irene with the Sun (dist. to the Sun = 2.721 AU; magn. = 10.0)
2018 07 24 03:50 Minimum of the variable star
Algol (beta Persei)
2018 07 24 11:02 Maximum of the variable star delta Cephei
2018 07 24 14:07 Opposition of the asteroid 140 Siwa with the Sun (dist. to the Sun = 2.149
AU; magn. = 10.4)
2018 07 25 13:18 Maximum of the variable star eta Aquilae
2018 07 27 00:38 Minimum of the variable star Algol (beta Persei)
2018 07 27 05:14 OPPOSITION of Mars with the Sun
2018 07 27 05:44 Moon at apogee (geocentric dist. = 406223 km)
2018 07 27 20:20 FULL MOON (total eclipse of the Moon
partly visible in SCARBOROUGH)
2018 07 28 04:23 Meteor shower : Piscis Austrinids (5 meteors/hour at zenith; duration = 26.0 days)
2018 07 29 19:49 Maximum of the variable
star delta Cephei
2018 07 29 21:27 Minimum of the variable star Algol (beta Persei)
Generated using COELIX software