Lunar Eclipse Images Taken By BAS Members - 27th July 2018 Darren Gamlin
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Bristol Astronomical Society Information Leaflet August 2018
Lunar
Eclipse
27th July 2018
Images
Taken By
BAS Members
Darren Gamlin
Nigel Wakefield Robert Massey
1
Latitude, Longitude: 51o 27.3′ N, 2o 35.5′ W (Bristol, UK)
August 2018: Observing Calendar Time zone: +0:00 DST observance: Europe
S unday Monday Tuesday Wednesday Thursday Friday S aturday S aturday Observing
1 2 3 4
Twi A: 2:42 Twi A: 2:46 Twi A: 2:50 Twi A: 2:54 No Public
Sunrise: 5:34 Sunrise: 5:35 Sunrise: 5:37 Sunrise: 5:38 Observing
Sunset: 21:00 Sunset: 20:58 Sunset: 20:56 Sunset: 20:55
Twi A: 23:51 Twi A: 23:47 Twi A: 23:43 Twi A: 23:39
Moonrise: 23:08 Moonrise: 23:29 Moonrise: 23:51 Moonrise: none
Moonset: 10:12 Moonset: 11:20 Moonset: 12:29 Moonset: 13:40
5 6 7 8 9 10 11
Twi A: 2:58 Twi A: 3:02 Twi A: 3:05 Twi A: 3:09 Twi A: 3:12 Twi A: 3:16 Twi A: 3:19 No Public
Sunrise: 5:40 Sunrise: 5:41 Sunrise: 5:43 Sunrise: 5:44 Sunrise: 5:46 Sunrise: 5:48 Sunrise: 5:49 Observing
Sunset: 20:53 Sunset: 20:51 Sunset: 20:49 Sunset: 20:48 Sunset: 20:46 Sunset: 20:44 Sunset: 20:42
Twi A: 23:35 Twi A: 23:31 Twi A: 23:27 Twi A: 23:23 Twi A: 23:20 Twi A: 23:16 Twi A: 23:12
Moonrise: 0:16 Moonrise: 0:45 Moonrise: 1:22 Moonrise: 2:08 Moonrise: 3:07 Moonrise: 4:16 Moonrise: 5:35
Moonset: 14:54 Moonset: 16:08 Moonset: 17:22 Moonset: 18:30 Moonset: 19:29 Moonset: 20:18 Moonset: 20:58
12 13 14 15 16 17 18
Twi A: 3:22 Twi A: 3:25 Twi A: 3:29 Twi A: 3:32 Twi A: 3:35 Twi A: 3:38 Twi A: 3:41 No Public
Sunrise: 5:51 Sunrise: 5:52 Sunrise: 5:54 Sunrise: 5:55 Sunrise: 5:57 Sunrise: 5:59 Sunrise: 6:00 Observing
Sunset: 20:40 Sunset: 20:38 Sunset: 20:36 Sunset: 20:34 Sunset: 20:32 Sunset: 20:30 Sunset: 20:28
Twi A: 23:09 Twi A: 23:05 Twi A: 23:02 Twi A: 22:58 Twi A: 22:55 Twi A: 22:51 Twi A: 22:48
Moonrise: 6:57 Moonrise: 8:20 Moonrise: 9:40 Moonrise: 10:58 Moonrise: 12:12 Moonrise: 13:24 Moonrise: 14:33
Moonset: 21:30 Moonset: 21:58 Moonset: 22:22 Moonset: 22:46 Moonset: 23:10 Moonset: 23:36 Moonset: none
19 20 21 22 23 24 25
Twi A: 3:43 Twi A: 3:46 Twi A: 3:49 Twi A: 3:52 Twi A: 3:55 Twi A: 3:57 Twi A: 4:00 No Public
Sunrise: 6:02 Sunrise: 6:03 Sunrise: 6:05 Sunrise: 6:07 Sunrise: 6:08 Sunrise: 6:10 Sunrise: 6:11 Observing
Sunset: 20:26 Sunset: 20:24 Sunset: 20:22 Sunset: 20:20 Sunset: 20:18 Sunset: 20:16 Sunset: 20:14
Twi A: 22:45 Twi A: 22:41 Twi A: 22:38 Twi A: 22:35 Twi A: 22:32 Twi A: 22:29 Twi A: 22:25
Moonrise: 15:37 Moonrise: 16:37 Moonrise: 17:32 Moonrise: 18:19 Moonrise: 19:00 Moonrise: 19:35 Moonrise: 20:04
Moonset: 0:04 Moonset: 0:37 Moonset: 1:15 Moonset: 2:00 Moonset: 2:51 Moonset: 3:48 Moonset: 4:48
26 27 28 29 30 31 Notes: Saturday observing
Twi A: 4:02 Twi A: 4:05 Twi A: 4:07 Twi A: 4:10 Twi A: 4:12 Twi A: 4:15 Civil twilight = sun at the BAS Failand
Sunrise: 6:13 Sunrise: 6:14 Sunrise: 6:16 Sunrise: 6:18
o Observatory will
Sunrise: 6:19 Sunrise: 6:21 6 below horizon;
resume in Sept.
Sunset: 20:12 Sunset: 20:10 Sunset: 20:07 Sunset: 20:05 Sunset: 20:03 Sunset: 20:01 Astronomical
o
following completion
Twi A: 22:22 Twi A: 22:19 Twi A: 22:16 Twi A: 22:13 Twi A: 22:10 Twi A: 22:07 twilight = sun 18 of the Observatory
Moonrise: 20:30 Moonrise: 20:53 Moonrise: 21:14 Moonrise: 21:35 Moonrise: 21:56 Moonrise: 22:20 below horizon improvement works
Moonset: 5:52 Moonset: 6:58 Moonset: 8:04 Moonset: 9:12 Moonset: 10:21 Moonset: 11:31 (Twi A)
DATA: www.sunrisesunset.com 2 3
The Sun The Sun - Solar Activity Forecast
Forecast of Solar and Geomagnetic Activity: 23 July - 18 August 2018
Solar activity is expected to be very low throughout the outlook period.
No proton events are expected at geosynchronous orbit.
The greater than 2 MeV electron flux at geosynchronous orbit is expected to
reach high levels on 23-31 Jul and moderate levels are expected on 01-11,
and 18 Aug. Normal levels are expected throughout the remainder of the
outlook period.
Geomagnetic field activity is likely to reach G1 (Minor) geomagnetic storm
levels on 24 Jul due to the influence of a negative polarity coronal hole high
speed stream. Active conditions are expected on 23, 25 Jul and 17 Aug due
to the influence of multiple, recurrent coronal hole high speed streams. Qui-
et and quiet to unsettled conditions are expected throughout the remainder
of the outlook period.
(CH HSS = Coronal Hole High Speed Stream)
12:00 , 15th Aug. 2018
www.heavens-above.com 4 www.swpc.noaa.gov 5
The Moon - Phases & Events Lunar Feature : Mare Serenitatis
(L No. from the ‘Lunar 100’ List - by Charles A. Wood, Sky & Telescope magazine, April 2004)
Mare Serenitatis ("Sea of Serenity") is a lunar mare located to the east of Mare
Imbrium on the Moon. Its diameter is 674 km (419 mi) long covering about 7.5% of
the circumference of the Moon. In the image above, Mare Serenitatis dominates
most of the region. Also visible are the Crater Posidonius (near the top of the pho-
to), Crater le Monnier (the dark, semi-circular spot slightly south of Posidonius) and
the sinuous Dorsa Smirnov (snake-like formation running N to S at the centre)
Dorsa Smirnov is a system of wrinkle ridges that run North-South along the Eastern
side of Mare Serenitatis. As it is a low profile object, rising only a few hundred me-
tres in height above the basaltic plain, it is most easily seen at local sunrise and
sunset. The ridge itself is a dark object on a dark background. Dorsa Smirnov is the
name given to the Northern-most ridge; the Southern portion is called Dorsa Lister,
though together they comprise one single large ridge feature.
www.timeanddate.com 6 www.heavens-above.com www.visit-the-moon.com; © Andrew M. Bray 7 www.fullmoonatlas.com
www.stardate.org/nightsky/moon
The Planets - Mercury & Venus The Planets - Mars & Jupiter
Mercury Mars
Jul – Sep 2018: 15 o FOV Jul – Dec 2018: 10 o FOV
Venus Jupiter
Jul – Sep 2018: 20 o FOV
www.in-the-sky.org 8 www.in-the-sky.org 9
The Planets - Saturn & Uranus The Planets - Neptune & Pluto (DP)
Saturn Neptune
Uranus Pluto (DP)
www.in-the-sky.org 10 www.in-the-sky.org 11
The Planets - Observing Notes (1) The Planets - Observing Notes (2)
Mercury: Mercury, having passed between the Earth and Sun Jupiter: Jupiter can be seen in the southwest soon after sunset at the start
(inferior conjunction) on August 9th, becomes visible after the 20th of the month. It shines at magnitude -2.1 (falling to -1.9 during the month)
before reaching greatest elongation east of the Sun on August and has a disk some 38 (falling to 35) arc seconds across.
26th. Then, some 18 degrees from the Sun, it rises before 5 am shin- Jupiter's equatorial bands, sometimes the Great Red Spot and up to four of
ing at magnitude zero. its Gallilean moons will be visible in a small telescope. Sadly, moving slowly
Venus: Venus, can be seen low in the west after nightfall sinking towards westwards in Libra during the month, Jupiter is heading towards the south-
the horizon as the month progresses. During August, its illuminated phase ern part of the ecliptic and will only have an elevation of ~15 degrees after
sunset.
thins from ~57% to ~29% but, at the same time, the angular diameter of its
disk increases from 20 to 29 arc seconds. The surface area reflecting the Saturn: Saturn reached opposition on the 27th of June, so is now low (at
Sun's light becomes greater and so the brightness increases from -4.3 to an an elevation of ~14 degrees) in the west-southwest as darkness falls lying
outstanding -4.6 magnitudes. Venus moves towards Spica in Virgo as Au- above the 'teapot' of Sagittarius. Held steady, binoculars should enable you
gust progresses and ends the month just one degree below the star. Sadly, to see Saturn's brightest moon, Titan, at magnitude 8.2. A small telescope
however, they are then only ~10 degrees above the western horizon after will show the rings with magnifications of x25 or more and one of 6-8 inches
sunset. aperture with a magnification of ~x200 coupled with a night of good
Mars: Mars came to its closest opposition to Earth since 2003 on the 27th "seeing" will show Saturn and its beautiful ring system in its full glory.
July but, sadly two things conspire to limit our views. From the UK its maxi- The two outermost rings, A and B, are separated by a gap called Cassini's
mum elevation when on the meridian will be only 12 degrees when ob- Division which should be visible in a telescope of 4 or more inches aper-
served from a latitude of +52 degrees. The second problem is that, as ture. Lying within the B ring, but far less bright and difficult to spot, is the C
sometimes happens, Mars is now suffering a major dust storm which, at the or Crepe Ring. Saturn’s disk has an angular size of 18 arc seconds falling to
end of July, was making it very difficult to observe any features on the sur- 17 during the month. Its brightness reduces from +0.2 to +0.4 magnitudes
face. These can happen every six to eight years and can last for several as the month progresses.
months. A small scale dust storm began on May 30th and, by the 20th of
Neptune: Neptune comes into opposition - when it is nearest the Earth -
June, had engulfed the whole planet. Sadly, it could take as long as Sep-
on the 7th of September, so will be well placed both this month and
tember for the dust to settle thus greatly inhibiting our view of Mars this
next. Its magnitude is +7.9 so Neptune, with a disk just 3.7 arc seconds
apparition. However, it does look as though the South Polar Cap is still visi-
across, is easily spotted in binoculars lying in the constellation Aquarius over
ble. Mars begins the month rising just after sunset shining at its peak mag-
to the left of Lambda Aquarii. It rises to an elevation of ~27 degrees when
nitude of -2.8 but this falls to -2.2 by month's end. Its angular size exceeds
due south. Given a telescope of 8 inches or greater aperture and a dark
24 arc seconds until August 8th and falls to 21 arc seconds by the start of
transparent night it should even be possible to spot its moon Triton.
September.
www.jb.man.ac.uk 12 www.jb.man.ac.uk 13 www.in-the-sky.org
Planetary / Lunar
Late Evening August Sky Positions
This map shows the constellations observable during 15 Aug
August in late evening.
Now that the evenings are drawing in, the night sky
gets darker earlier so encouraging one to go out to
observe.
High over head towards the north lies Ursa Major.
As one moves southwards one first crosses the con-
stellation Hercules with its magnificent globular clus-
ter, M13, and then across the large but not promi-
nent constellation Ophiucus until, low above the
southern horizon lie Sagittarius and Scorpio.
To the right of Hercules lie the arc of stars making up
Corona Borealis and then Bootes with its bright star
Arcturus.
Rising in the east is the beautiful region of the Milky
Way containing both Cygnus and Lyra.
Below is the constellation of Aquila, the Eagle. The
three bright stars Deneb (in Cygnus), Vega (in Lyra)
and Altair (in Aquila) make up the "Summer Trian-
gle".
Constellations Culminating in August:
• Aquila
• Lyra
• Sagitta
• Saggitarius
1 Aug 23:00
15 Aug 22:00
31 Aug 21:00
www.jb.man.ac.uk 14 15 www.heavens-above.com
ISS - Visible Passes from Bristol Comets & Asteroids
The tables below list the brightest comets and asteroids, down to approx.
magnitude 14 which may be observable from Bristol during the month.
Further details and finder
charts can be found at:
Comets
• www.in-the-sky.org/data/
comets.php
This plot shows the orbital height of the ISS over the last year. Clearly visible are the re-boosts
which suddenly increase the height, and the gradual decay in between.
• www.aerith.net/comet/weekly/
current.html
The height is averaged over one orbit, and the gradual decrease is caused by atmospheric • www.cometchasing.skyhound.com
drag. Asteroids
As can be seen from the plot, the rate of descent is not constant and this variation is caused • www.heavens-above.com/
by changes in the density of the outer atmosphere due mainly to solar activity. asteroids.aspx
Estimating ISS position is on the basis of NORAD/Celestrak orbital data downloaded on 27 July 2018.
www.heavens-above.com 16 www.nasa.gov www.in-the-sky.org 17 www.heavens-above.com
DSO Targets Observing Opportunities in August
The tables below list the rising and setting times of some of the brightest DSOs visible in the Monthly Events
sky from Bristol during August (exact times cited for 15th of the month). 11th: Observe Mars - planetary features Syrtis Major and the Hellas Basin may be visible
12th Perseid Meteor Shower - on the mornings of August 12th and 13th , midnight to
dawn, look out for the Perseid meteor shower
If clear, these mornings should give us a chance of observing the Perseid meteor
shower - produced by debris from the comet Swift-Tuttle. The early morning of the
12th August will give us the best chance, if clear, of viewing the shower, but the peak
is quite broad and so it is well worth observing on the nights before and after. Most
meteors are seen looking about 50 degrees from the "radiant" which lies between
Perseus and Cassiopeia. The really good news is that, this year, these nights are only
a few days after New Moon on the 11th so that the Moon will have set by the time
we should look out for meteors and its light will not hinder our view.
The coloured charts below indicate the altitude of GCs & Galaxies in the sky at different times
of day. Black or red stripes indicate objects that are low in the sky and may be hard to see. 14th: Venus below a thin crescent Moon, after sunset
20th: Two great Lunar Craters, Tycho and Copernicus - both near the terminator
www.in-the-sky.org 18 Data shown for 15 Aug 2018 at 22:00 www.jb.man.ac.uk 19 www.britastro.org www.in-the-sky.orgLyra - Star Chart Lyra - Vega
Vega is a brilliant magnitude +0.03 blue-
tinged white main sequence star. It's margin-
ally brighter than Capella and slightly fainter
than Arcturus, making it the second brightest
star in the northern section of sky. With a dec-
lination of 38o North, Vega appears high in the
sky and sometimes overhead from many northern temperate locations.
It's probably unsurprising, given its brilliance and prominent northern decli-
nation, that Vega is one of the most investigated stars. It was one of the first
stars to have its distance determined by parallax, the first star other than
the Sun to be photographed and the first to have its spectrum evaluated.
Vega is a class A0Va star that's positioned within the main sequence of the
Hertzsprung-Russell diagram. It's a nearby star, only 25 light-years distant,
and relatively young at 455 million years. This is about 1/10 the age of the
Sun. However, Vega is burning through its hydrogen fuel at a fast rate and is
expected to become an M class red giant in approx. 500 million years time.
For comparison, the same scenario will not affect the Sun for another 5 bil-
lion years. Even though it's more than twice as massive and over 40 times
more luminous than the Sun, Vega is still not large enough to explode as a
supernova and will end its life, just like
The Lyra constellation represents the lyre, a musical instrument with strings
our star, as a white dwarf.
used in antiquity and later times. The constellation is associated with the
myth of the Greek musician and poet Orpheus. It was first catalogued by the Recent observations suggest that Vega is
astronomer Ptolemy in the 2nd century. slightly variable and of the Delta Scuti
type. If confirmed, it would be the bright-
Lyra contains Vega, the fifth brightest star in the sky and second brightest
est example of this type of star.
star in the northern hemisphere, and the famous variable star RR Lyrae. It is
also home to several notable deep sky objects, including the globular cluster Surrounding Vega are disks of dust and
Messier 56, the planetary nebula Messier 57 (the Ring Nebula), the merging debris that extend for hundreds of astro-
triplet of galaxies NGC 6745, and the open cluster NGC 6791. nomical units (AU).
20 www.constellation-guide.com 21 www.freestarcharts.comLyra - Epsilon
Boötes
Lyrae--Arcturus
The Double Double Lyra - Messier 56 (Globular Cluster)
Of all multiple star systems consisting of at least three stars, perhaps the M56 is a faint distant globular cluster in Lyra that's positioned close to the
finest and most celebrated of all is Epsilon (ε Lyr) Lyrae. Positioned just over Cygnus border. At magnitude +8.3, it's one of the dimmer Messier globulars
1.5 degrees to the northeast of Vega and shining at magnitude 3.9 is Epsilon and a challenging binocular object, but easily visible in medium size amateur
Lyrae. The star at first glance probably won't seem at all remarkable, but on scopes. Instruments of the order of 250mm (10-inch) aperture or greater will
closer inspection and especially if you have sharp eyesight, you may notice resolve some of the member stars. An unusual feature of this object is that it
that Epsilon Lyrae is in fact a double star consisting of two almost identical follows a retrograde orbit through the Milky Way.
white stars. The stars are named Epsilon1 and Epsilon2 Lyrae and have a M56 is located almost halfway along an imaginary line connecting beautiful
separation of 208 arc seconds. double star Albireo (β Cyg - mag. +3.1) with Sulafat (γ Lyr - mag. +3.3). Since
Epsilon1 and Epsilon2 are split in 7x35, 10x50 and it's located in a dense part of the Milky Way, it's easy to miss, especially with
20x80 bins without problem. Of the two stars, the small scopes. Positioned not far from M56 is the only other Messier object in
northern one is Epsilon1 and the southern one, Lyra, the Ring Nebula (M57).
Epsilon2. Remarkably, this is not where the story Through 7x50 or 10x50 binoculars, M56 appears
ends as both Epsilon1 and Epsilon2 themselves are at best as a faint slightly fuzzy star. When
double stars; hence the nickname "The Double viewed with larger 70mm or 80mm models, it
Double". Low Power / Binocular View
looks obviously non-stellar. A 100mm (4-inch)
However, you won't be able to further split these telescope shows the cluster as a faint, round,
two stars with binoculars; it requires much higher diffuse ball of light with very little or no details
magnification. A small 70mm to 80mm telescope discernible. A noticeable 5th magnitude star lies
at about 120x magnification will do the job, if the less than a degree to the northwest of the clus-
seeing conditions are good. In fact, this example is ter. It's possible to resolve some of the outer Sketch of M56 at 120x
a good test of the seeing conditions. If you can split stars using 250mm (10-inch) scopes with the brightest members being of
Epsilon Lyrae into its four components with a small 13th magnitude. The cluster displays a gradual, soft brightening from the
80mm Refractor 120x telescope, then you're night is off to a good start as outer regions towards the core. In total, it measures 8.8 arc minutes alt-
the observing conditions are superb. All 4 stars appear off white in colour. hough visually it appears about half this size.
All four stars are gravitationally bound and it is estimated that the two com- M56 is 32,000 light-years distant, which corresponds to a spatial diameter of
ponents of Epsilon1 take 1200 years to complete one orbit compared to 585 84 light-years. It contains only a dozen or so variable stars and is estimated
years for the stars of Epsilon2. The Epsilon Lyrae system is located 162 light- to be 13.7 billion years old.
years from Earth. In 1985, a fifth component of the system orbiting one of The globular is best seen from the Northern Hemisphere during the months
the Epsilon2 pair was detected by speckle interferometry. of June, July and August.
22 23 www.freestarcharts.comLyra - Messier 57 (Ring Nebula) Aquila - Star Chart
M57, the Ring Nebula, is a planetary nebula located in the constellation of
Lyra. It's probably the most well-known, studied and photographed object
of its kind and a perennial favourite with amateur astronomers.
The nebula is relatively bright at magnitude +8.8 and easy to locate. It can
be found about 40% the way along an imaginary line connecting stars, Sheli-
ak (β Lyr - mag. +3.5) and Sulafat (γ Lyr - mag. +3.2). For Northern Hemi- Tarazed
NGC 6709
sphere observers, it appears high in the sky during the warm summer R
months although from southern latitudes it appears much lower down. NGC 6781
M57 was discovered by Antoine Darquier de Pellepoix in January 1779 and
Charles Messier discovered it independently later the same month, and in-
cluded it in his catalogue. 14
15
M57 is a difficult 10x50 binocular object, appearing
57 12
at best as a faint out of focus star. It's certainly much
easier to spot when using larger 20x80 models. Small
telescopes fair better and a 100mm (4-inch) scope
reveals a small grey puffed out, slightly elliptical
patch of light. However, seeing the ring shape with it
central hole is challenging even when using averted
vision. When viewed through a 200mm (8-inch) tele- Sketch of M57 at 240x
scope, the shape is much clearer with finer details also visible. The constellation’s name means “the eagle” in Latin, representing the eagle
of the Roman god Jupiter in mythology. Aquila is home to two very famous
Very large amateur scopes show more intricate details, but the 15th magni-
stars, Altair and Tarazed, as well as to several interesting deep sky objects:
tude central star at the heart of the Ring Nebula is difficult to spot. Howev-
the planetary nebulae NGC 6803, NGC 6804, NGC 6781, the Phantom Streak
er, it's much easier to image.
Nebula (NGC 6741), the open clusters NGC 6709 and NGC 6755, and the
The nebula was formed when a shell of ionized gas was expelled by a red dark nebula B143-4.
giant star that was in the process of becoming a white dwarf. It is expanding
Aquila has seven stars with known planets and contains no Messier objects.
at the rate of about 1 arc-second per century. The Ring Nebula belongs to
The brightest star in the constellation is Altair, Alpha Aquilae, which is also
the class of planetary nebulae known as bipolar nebulae. It has a thick equa-
the 12th brightest star in the sky. There are two meteor showers associated
torial ring that noticeably extends the structure through its main axis of
with Aquila: the June Aquilids and the Epsilon Aquilids.
symmetry.
24 25 www.constellation-guide.comAquila - Altair (α Aquilae) Aquila - Tarazed & DSOs
Altair is the 12th brightest star in the sky, with an apparent visual magni- Tarazed – γ Aquilae (Gamma Aquilae)
tude of 0.77. It is an A-type main sequence star (hydrogen fusing dwarf) that Tarazed is the second brightest star in Aquila. It is a class K bright giant with
has three visual companion stars that are not physically close to it but ap- an apparent visual magnitude of 2.72, approximately 461 light years distant.
pear along the same line of sight in the sky. Lying only 16.8 light-years away, Tarazed is 2960 times more luminous than the Sun and has a radius of 110
Altair is one of the closest stars to Earth that is visible to the naked eye. The solar, taking up about 0.5 AU in the sky. It is a known source of X-rays.
star was classified as a Delta Scuti variable in 2005. It exhibits variations in Tarazed is about 100 million years old and is burning He into C in its core.
luminosity over periods that range from 0.8 to 1.5 hours.
Tarazed is a good star to observe with binoculars or a small aperture tele-
Altair has 1.8 times the mass and 10.6 times the luminosity of the Sun. Be- scope, since you can easily observe its beautiful red-orange colour. Smaller
cause it rotates very rapidly (286 km/s velocity at the equator - rotational aperture telescopes (60—80 cm) are best for observing the colours of the
period of about 9 hours), Altair’s shape is not spherical, but flattened at the brightest stars (down to about 5th magnitude), because larger apertures
poles. Consequently, Altair’s polar diameter is estimated to be 15-25 per- with higher light-gathering power will simply wash out their splendid col-
cent smaller than its equatorial diameter. The star also moves across the sky ours.
relatively quickly - it shifts by about a degree in 5000 years.
The “E” or “Barnard’s E” Nebula: The "E" or "Barnard's E" Nebula (officially
In 2007, astronomers used a suite of 4 telescopes on Mt. Wilson, California, designated as Barnard 142 and 143) is a pair of dark nebulae that resemble
(Centre for High Angular Resolution Astronomy - CHARA) to capture an ac- a capital letter E. It is a well-defined dark area on a background of the Milky
tual infra-red image of Altair. This was the first time anyone has seen the Way consisting of countless stars of all magnitudes and is a great target for
surface of a relatively tiny hydrogen-burning star like our own sun. 50mm binoculars on a dark night. Its size is about that of the full moon, or
Utilising the technique of IR interferometry the facility operated with an roughly 0.5 degrees, and its distance from earth is estimated at about 2,000
’equivalent’ telescope mirror of 265 by 195 meters in size (approx. 25 times light years. It lies about 1.5 degrees to the west of Tarazed (in the same bin-
the resolution of HST). See the images of Altair below (from left to right): ocular field).
standard optical image, actual CHARA IR image and an artist’s rendition of NGC 6709 (Open Star Cluster): An open star cluster located five degrees
ALTAIR based upon the CHARA data: southwest of Zeta Aquilae and makes a slender right angle triangle with Zeta
and Epsilon Aquilae. It appears as a bright misty glow in small binoculars and
small telescopes show 30—60 stars spread in a diameter of 15 arcminutes,
arranged in chains and bunches.
NGC 6781 (Planetary Nebula): NGC 7681 makes a short isosceles triangle
with Delta and Mu Aquilae and lies about 8 degrees west-south-west of Al-
tair. It is easily within the reach of 4 inch telescopes and at ~50x mag. ap-
pears as a round and fairly large planetary nebula.
26 27 www.freestarcharts.comSociety News
Programme of Events 2018
(At Bristol Photographic Society, Station Road, Montpelier, Bristol. BS6 5EE )
As normal over the summer period our meetings are less frequent and are normally given by
BAS members. Please check the BAS website regularly for more details.
Failand Observatory Improvement Project - Update
During June and July, work has been completed to dismantle the existing large equatorial
mount in the dome, clear the concrete plinth and temporarily install one of the Society
Meade LX200 telescopes on the plinth. We are now seeking to acquire and install a larger
and more modern telescope system with much improved observing and imaging capabilities.
In addition, we’re planning to install toilet facilities at the Observatory over the coming
months. The photos below show progress with work in the dome.
Bristol Astronomical Society (Registered Charity No. 299649)
www.bristolastrosoc.org.uk
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