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Society News
Saturday Open Observing
John Willis is once again the organiser for the Saturday open observing sessions
at the observatory. He is looking for more volunteers to join the rota so if you can
help please see John at one of our meeting or email him at
[email protected] the more people there are on the rota
the fewer evenings each person has to do.
Bristol Astronomical Society Information Leaflet
All Times Are British Sumer Time BST
Solar Observing
Our solar observing sessions at Tyntesfield and Bristol Zoo begin again shortly
and we are also looking for volunteers to help out at these events. To improve the
chances of having clear skies the Tyntesfield events will be held on Saturdays and
Sundays. The events at Bristol Zoo are held during the week. If you can help at
any of these events please contact Allan McCarthy for Tyntesfield and Mel Rigby
or John Willis for Bristol Zoo.
Website
The society’s website was recently ‘attacked’ by a spam site, this caused the us
to exceed our download limit an meant that the site was not available for around a
week. The part of the site that was involved was no longer in use and has now
been completely deleted.
It is hoped that our new website will be up and running in the near future.
Programme of Events for April 2013
All meetings are held at Bristol Grammar School, University Road BS8 1SR
5th
Apr Roger Dymock - Project Alcock
12th Apr
Club Night - Allan McCarthy
19th Apr Prof. Mark Birkinshaw - TBA
26th Apr
Club Night - John Willis
Don’t forget to check out the BAS website where you can get all the latest info
about the society. http://www.bristolastrosoc.org.uk/
Comet C/2011 L4 Panstarrs - Chris Lee
Bristol Astronomical Society are a Registered Charity, No. 299649
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1
April 2013
TheSun&Moon
The Sun
Date
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Sun and Moon Rise and Set times for April 2013
Sun
Moon
Rise
Set
Rise
06:46
19:44
01:08
06:43
19:45
02:07
06:41
19:47
02:56
06:39
19:49
03:36
06:37
19:50
04:09
06:34
19:52
04:37
06:32
19:54
05:01
06:30
19:55
05:25
06:28
19:57
05:48
06:25
19:59
06:12
06:23
20:00
06:38
06:21
20:02
07:08
06:19
20:04
07:42
06:17
06:15
06:12
06:10
06:08
06:06
06:04
06:02
06:00
05:58
05:56
05:54
05:52
05:50
05:48
05:46
05:44
20:05
20:07
20:09
20:10
20:12
20:14
20:15
20:17
20:19
20:20
20:22
20:24
20:25
20:27
20:29
20:30
20:32
2
08:22
09:07
09:59
10:56
11:57
13:01
14:09
15:18
16:30
17:45
19:02
20:21
21:39
22:53
23:58
00:52
Failand Open Observing April 2013
Set
09:47
10:49
11:59
13:12
14:27
15:42
16:55
18:07
19:17
20:26
21:33
22:37
23:36
00:29
01:15
01:55
02:29
02:59
03:25
03:49
04:12
04:36
05:01
05:30
06:04
06:46
07:37
08:39
09:48
Please check the Open Observing Page on the website for details of this months’
observatory openers
All welcome
Including Family, Friends, Neighbours,
with or without telescopes binoculars etc.
No Astronomical knowledge or skill required.
Please:
Contact the opener by email if you want to bring more than 4 visitors or to
ask if it appropriate to run an activity on the night.
Use the status message on www.bristolastrosoc.org.uk to check if the session
is running.
Email [email protected] if you want to join the rota.
See the charts on open observing page on the website to see what objects are
visible that weekend.
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Double Star of the Month
Alpha (α) Canum Venaticorum - RA 12h 56m 01s - Dec +38° 12′ 06′′
Alpha Canum Venaticorum is also known as Cor Coroli (Charles’s Heart) it is the
brightest star on the constellation of Canes Venatici it is also a double star.
The brighter of the 2 stars is α² Canum Venaticorum is also a variable star. It is,
an A-class (A0) white dwarf star which varies between +2.84 and +2.98, with a
period of 5.47 days. The star is the prototype of a class of variable stars, known as
α² Canum Venaticorum stars.
These stars have a peculiar chemical makeup with the atmosphere containing
higher than average levels of silicon, mercury and europium the stars also have
extremely strong magnetic fields, about 5,000 times as strong as the Earth's.
These magnetic fields are thought to produce massive starspots which causes the
brightness of α² Canum Venaticorum stars to vary during their rotation.
The fainter of the pair α1 Canum Venaticorum is a magnitude +5.60 F-class (F0)
main sequence dwarf star.
The pair are separated by 19 arcseconds and should be easily split with a small
telescope.
The Sun & Moon
The Sun
The Sun remains pretty active with plenty of active
regions visible.
The image (right), from the SOHO satellite shows the
Sun on March 18th and has at least 7 active regions
visible.
Please take care when observing the Sun and never
look directly at it even with the naked-eye as it can
cause permanent damage your eyes.
The Moon
Apogee - 15th 23:23 (404,864 km) Perigee - 27th 20:49 (362,267 km)
10th
10:35
18th
13:31
25th
20:57
3rd
05:37
Partial Penumbral Eclipse.
There will be a partial penumbral eclipse of the Moon on the evening of the 25th,
the Moon rises at 20:21 and greatest eclipse will occur at 21:07 so the Moon will
still be very low in the south-eastern sky. The Penumbral shadow will leave the
Moon at around 23:00, this type of eclipse is very spectacular and any change can
be difficult to detect so if you are out in the evening of the 25th have a look at the
Moon and see if you and detect any dimming in the northern part of the Moon.
26 Day Old Moon
At 26 days old the Moon now appears as a thin crescent and rises in the early
hours of the morning.
Lying on the terminator is the crater Aristarchus which is generally considered to
be the brightest crater on the lunar surface and is visible when the dark part of the
moon is illuminated by Earthshine. Aristarchus has a diameter 41km, it has high
terraced walls and steep outer slopes. The crater floor is fairly flat with a small
central mountain peak. Aristarchus is the site of a large number Transient Lunar
Phenomenon (TLP) reports which include temporary obscurations and colour
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3
TheSun&Moon
Messier of the Month
changes in and around the crater.
Messier 87 (NGC 4486) - RA 12h 30m 49s - Dec +12° 23′ 28′′
Almost on the lunar equator close to the western limb you
will find lies the large wailed plain Grimaldi. The plain has a
diameter of 228 km and is filled with very dark lava making
it fairly easy to spot. Meandering across the south-eastern
floor there is a 236 km long rille, Rimae Grimaldi. There are
a number of small hills in the north of the plain as well as
few small craterlets. There are numerous shaded bands
across the floor of the plain.
Messier 87 is a super massive elliptical galaxy that lies at the heart of the ComaVirgo cluster, it is also known a Virgo A. M87 is
the largest galaxy in the cluster and at magnitude
+8.6 it is one of the brighter members of the cluster.
Just to the south of the lunar equator lies the crater Billy, this
48km wide crater has high wall and a very flat floor which is
also fairly dark making it quite easy to pick out against the
bright surrounding area.
Further to the south lies Schickard a large walled plain, over
215 km in diameter. The floor of Schickard is mottled with a number of darker
areas, there are also a number of small craters and hills. The walls surrounding the
plain contain a number of peaks which rise to over 2700m.
This huge galaxy is visible in binoculars and small
telescopes. Unlike a spiral galaxy there is no detail
visible in M87 which looks similar to an unresolved
globular cluster.
There are a number of other galaxies in the vicinity
of M87 including M59, M60, M84, M86, M88,
M90, M99 and M110.
M49, M53, M61, M64 AND M100 lie a bit further
away but still in the same area of the sky.
M87 lies just under halfway along a line drawn
from epsilon (ε) Virginis (Vindemiatrix) and beta (β) Leonis (Denebola).
Have fun sweeping around this part of the sky, there are plenty more galaxies in
the area that did not make it in to Messiers catalogue for you to locate.
4
21
The Planets
Mercury
Comets C/2011 L4 PANSTARRS
Date
RA
Dec
Mag Phase Dia
Rise
Transit
Set
52%
01
23h 05m -07° 43' +0.27
7.2" 06:09
11:34
17:00
15
00h 13m -01° 22' -0.11 71% 6.1" 05:51
11:47
17:43
30
01h 48m +09° 23' -0.97 91% 5.3" 05:31
12:22
19:31
Mercury is not visible from the UK this month. If you are heading south for a
early holiday the innermost planet will be visible in the north-eastern sky before
sunrise.
Date
01
15
30
RA
Dec
Mag
00h 50m +04° 04' -3.91
01h 55m +10° 50' -3.90
03h 07m +17° 08' -3.90
Venus
Phase Dia
100% 9.7"
100% 9.7"
99% 9.8"
Rise
06:56
06:30
06:07
Transit
13:20
13:29
13:41
Set
19:43
20:28
21:17
Phase Dia
100% 3.9"
100% 3.9"
100% 3.8"
Rise
06:59
06:20
05:42
Transit
13:29
13:13
12:56
Set
20:00
20.06
20:12
Venus is not visible this month.
Mars
Date
01
15
30
RA
Dec
Mag
00h 56m +05° 23' +1.18
01h 38m +09° 47' +1.18
02h 21m +13° 48' +1.25
Mars passes through superior conjunction on the 17th and is not visible this
month.
Jupiter
Date
01/02
15/16
30
RA
Dec
Mag Phase
04h 41m +21° 49' -2.10 99%
04h 52m +22° 09' -2.03 99%
05h 04m +22° 30' -1.98 99%
Dia
36"
35"
34"
Rise
09:07
08:20
07:31
Transit
17:11
16:27
15:40
Set
01:15
00:35
23:50
Jupiter is visible in the south-western sky during the evening, by the end of the
month the giant planet will set shortly before midnight. Jupiter is moving through
the constellation of Taurus and can be seen amongst the stars of the Hyades.
Any small telescope will show the main belts of Jupiter also its four largest
moons. Large telescopes will reveal plenty of detail on the planet’s disc including
the famous Great Red Spot (GRS), a storm which has been raging for hundreds of
20
5
The Planets
Comet C/2011 L4 PANSTARRS
years ( it was first observed by Robert Hook in 1664). Below is a list of the times
when the GRS will be on the central meridian of the planet that are visible from
the UK during April.
Comet Panstarrs, like a number of comets, did not reach the brightness predicted
at the end of last year. Although it will be visible above the horizon throughout
the month (due to the fact that it is now circumpolar) it will be fading all the time
as it moves away from the Sun towards the depths of space, it will not return to
the inner solar system for around 110,000 years.
April 2nd 21:53; 4th 23:32; 7th 21:03; 9th 22:42; 12th 20:13; 14th 21:52;
16th 23:31; 19th 21:02; 21st 21:41; 26th 21:52; 28th 23:31.
The chart on page 20 shows the predicted path of the comet at 3 day intervals
throughout this month.
Saturn
Date
01/02
15/16
29/30
RA
Dec
Mag
14h 33m -12° 15' +0.24
14h 29m -11° 56' +0.17
14h 25m -11° 36' +0.13
Phase
100%
100%
100%
Dia
19"
19"
19"
Rise
22:02
21:02
20:01
Transit
03:02
02:03
01:04
Set
08:01
07:04
06:07
Saturn reaches opposition on the 28th of this month and will consequently be
visible throughout the hours of darkness. The ringed planet will be visible low in
the south-eastern sky in the constellation of Libra. The rings are currently tilted at
around 18 degrees as viewed form the Earth and are visible in small telescopes.
Saturn is one of the ‘must see’ objects in the night sky and it always has the
‘Wow’ factor when you first see it through a telescope.
Uranus
Date
01
15
30
RA
Dec
Mag
00h 32m +02° 45' +5.93
00h 35m +03° 04' +5.93
00h 38m +03° 22' +5.92
Phase Dia
100% 3.3"
100% 3.4"
100% 3.4"
Rise
06:46
05:52
04:55
Transit
13:03
12:11
11:15
Set
19:20
18:29
17:35
Uranus lies in the constellation of Pisces, it is too close to the Sun for observation
this month.
Neptune
Date
RA
Dec
Mag Phase Dia
01
22h 24m -10° 35' +7.95 100% 2.2"
15
22h 26m -10° 27' +7.94 100% 2.2"
30
22h 27m -10° 20' +7.92 100% 2.2"
Rise
05:46
04:52
03:54
Transit
10:55
10:02
09:04
Set
16:04
15:12
14:15
Neptune lies in he constellation of Aquarius and is not well placed for observation this month.
The comet has been spotted by a number of society members, I saw the comet on
the 17th of March close to the western horizon, it was much easier to spot than I
expected and the tail was quite prominent flowing vertically upward from the core
of the comet.
See the March issue of Eclipse for a round up of members observing reports on
the comet. Chris Lee did a couple of sketches of the comet the second of which
you can see on the front cover of this issue.
The comet begins the month in the constellation of Andromeda just below the
Andromeda Galaxy, M1, during the following week the comet moves past the
galaxy heading towards Cassiopeia. This should help you locate the comet and
will also give our astro–imagers a nice opportunity for a few pictures of these two
celestial ‘fuzzies’, the evenings of the 3rd, 4th and 5th should be the best as this is
when the two objects will apper closest to each other but any clear evening in the
first week of the month should be ok.
The comet should hopefully still be visible in binoculars and the both objects will
appear in the same field of view using 10x50s on the 3rd 4th and 5th.
The comet crosses the border into Cassiopeia on the 9th and on the following
evening it will pass close to NGC 147 (Caldwell 17) a magnitude +10.5 galaxy
which is a member of our local group
You will need a telescope to spot this galaxy and it neighbour NGC185 (Caldwell
18) magnitude +10.1. These two galaxies are gravitationally linked and are both
outlying satellite galaxies of M31.
On the 20th the comet passes between Shedir, (α) and Caph, (β) Cassiopeiae just
over halfway from alpha to beta.
The comet crosses the border the 28th ending the month in the constellation of
Cepheus.
If the weather improves and you do observe Comet Panstarrs please let me have a
report f you observation for Eclipse.
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The Sky this Month
The Sky looking East around midnight mid April 2013
Now that we have moved to British Summer Time (BST), spring is finally here,
and the bright constellations of winter, Orion, Taurus and Gemini are replaced by
the less conspicuous spring constellations of Coma Berenices, Virgo and Hydra.
However some of these constellations are very popular with deep-sky observers as
they are home to large clusters of galaxies.
High in the south you will find the constellation of Leo, it is easily recognisable
as, to me, it vaguely resembles the outline of a prone Lion.
The brightest star in Leo, shining at magnitude +1.35 is alpha (α) Leonis, Regulus;
which marks one of the front paws of the celestial lion. It lies at the bottom of the
asterism known as ‘the Sickle’ (a backwards ?) that represents the head and mane
of the lion. The ‘Sickle’ is formed by the stars alpha (α), eta (η), gamma (γ), zeta
(ζ), mu (μ) and epsilon (ε).
Lying below the body of the lion there are a number of galaxies including five
Messier objects M65, M66, M95, M95 and M105. M65, M66, along with NGC
3628, are known collectively as the ‘Leo Triplet’ and can be found just to the
south of theta (θ) Leonis. The other three Messier objects M95, M96 and M105
form another small group that lies just below the mid-point between alpha (α) and
theta (θ) Leonis.
One of the other highlights in Leo is the lovely double star gamma (γ) Leonis
(Algieba), this is a great double for small telescopes. The primary is a magnitude
+2.2 K-class yellow-orange giant, it’s companion is a magnitude +2.5 yellow Gclass star. The pair are separated by 4.4 arcseconds.
Just to the west of Leo lies the faint constellation of Cancer, which is home to one
of the loveliest open clusters in the sky, Praesepe, more commonly known as the
Beehive Cluster or M44. This large cluster of stars is just about visible with to the
naked-eye even from light polluted areas, and a stunning sight in binoculars and
small telescopes.
There is another of Messier’s open clusters in Cancer, M67, this cluster lies a little
over 1.5 degrees west of Acubens, alpha (α) Cancri. Due to its roughly triangular
shape it is known as the ‘Cobra’s Head’ or ‘King Cobra’ cluster.
Iota (ι) Cancri is a double star that lies in the north of the constellation. The star
consists of a magnitude +4.02 yellow G-class giant star, and a magnitude +6.58,
white A-class dwarf. The pair are separated by 30 arcseconds and are a lovely
sight in a small telescope.
18
7
8
17
The Sky looking North around midnight mid April 2013
Leo & Cancer
The Sky this Month
The Sky looking West around midnight mid April 2013
To the east and southeast of Leo lies the constellations of Coma Berenices and
Virgo. These two constellations are home to a huge group of galaxies known as
the Coma-Virgo cluster. Coma contains eight Messier objects M53, M64, M85,
M88, M91, M98, M99, and M100 and Virgo contains another eleven, M49, M58,
M59, M60, M61, M84, M86, M87, M89, M90, and M104. All these objects are
visible in amateur telescopes.
The constellation of Hydra can be found meandering across the horizon in south
and southwest, this is the largest constellation in the sky. Hydra is a relatively
faint constellation and it can be quite difficult to pick it out in the haze close to
the horizon. Hydra is home to three Messier objects, M48, an open cluster, M68 a
globular cluster and M83, a spiral galaxy.
Sitting along the length of Hydra are three small constellations, Corvus, Crater
and Sextans. Corvus is the most easterly of the trio and is probably the easiest to
identify, four of the brighter stars, beta (β), delta (δ), gamma (γ) and epsilon (ε)
Corvi form an irregular quadrilateral which stands out quite well in this sparsely
populated area of the sky. The most interesting ‘object’ in the constellation is a
pair of interacting galaxies known as the Antennae Galaxies (NGC 4038/NGC
4039) which can be found in the west of Corvus.
Moving west, Crater, is next, the base of the cup resembles the shape of Corvus,
only reversed, and is formed by alpha (α), beta (β), delta (δ), gamma (γ) Crateris.
Sextans is the last of the trio, this is a very faint constellation, its brightest star,
alpha (α) Sextantis is only magnitude +4.49. There is just one interesting deepsky object, NGC 3115, an almost edge on Lenticular galaxy which can be found
just over three degrees east of gamma (γ) Sextantis.
Lying just to the east of Leo and Coma Berenices you will find the ‘Kite’ shaped
constellation of Boötes, its brightest star is the magnitude -0.07 K-Class orange
giant, Arcturus.
Further east lies the constellation of Hercules which is home to two of Messier’s
globular clusters M13 and M92. M13 is the best globular cluster visible in the
northern half of the sky, it lies on the western side of the ‘Keystone’ asterism,
about a third of the way from eta (η) to zeta (ζ) Herculis. M92 lies to the north of
the ‘Keystone’ approximately midway between eta and iota (ι) Herculis. There is
a fairly bright planetary nebula (magnitude +9.3) which lies just over four degrees
east of Kornephoros; beta (β).
Lying between the constellations Boötes and Hercules is a small semi-circle of
stars that form Corona Borealis, near the centre of the semi-circle lies the famous
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9
10
15
The Sky looking South around midnight mid April 2013
Coma Berinices & Virgo
The Sky looking Overhead around midnight mid April 2013
The Sky this Month
variable star R Coronae Borealis. R CrB is the type star of a class of variables
which unlike most types of variables which brighten from their normal state, R
CrB type variables fade dramatically. The star is currently recovering from one of
the longest and deepest minima for many years, it faded to below magnitude +15.
Keep an eye on R Coronae as it returns to it’s normal brightness of magnitude +6.
Over in the western sky, Gemini (the Twins) remain visible until after midnight.
Castor (α Geminorum) is nice double star which is suitable for observers with
small telescopes. The components are both A-class stars, magnitudes +1.93 and
+2.97 separated by 6 arcseconds. Lying at the feet of Castor, just over 2 degrees
west of eta (η) Geminorum you will find M35, this open cluster is a stunning
sight through a telescope.
To the northwest of Gemini lies the constellation of Auriga which is home to
three of Messier’s open clusters, M36, M37 and M38 all of which are visible in
binoculars and small telescopes.
High overhead you will find the familiar pattern of 7 stars known as the ‘Plough’
or ‘Saucepan’ which is part of the constellation of Ursa Major. This pattern of
stars can be used as a guide to help you locate a number of other constellations.
The two end stars in the bowl, Dubhe and Merak are known as the ‘Pointers’ as
they point to Polaris, the ‘Pole Star’. Following a line from the other two stars in
the bowl to the south will bring you to Regulus the brightest star in Leo.
If you follow the curve of the handle towards the south, it will point you towards
the bright orange star Arcturus. If you continue the arc further to the south it will
lead you to the bright star Spica; the brightest star in Virgo.
There are a number of deep-sky objects in Ursa Major including 7 that made it
into Messier’s catalogue, M40, M81, M82, M97, M101, M108 and M109.
In the northern sky you will find Polaris; alpha (α) Ursa Minoris one of the most
important stars in the sky. Polaris lies just under than half a degree from the north
celestial pole, making it extremely useful for navigation.
Lying below Polaris you will find the ‘crooked house’ shape of Cepheus and the
W shaped Cassiopeia. The central star in the ‘W’, gamma (γ) Cassiopeiae is the
prototype of a class of eruptive type variables. Gamma is a naked eye variable
which varies irregularly in brightness between +2.20 and +3.40.
In the eastern sky the summer constellations of Lyra and Cygnus are now rising
before midnight. By the early hours of the morning Lyra will be at a reasonable
height, giving you the chance to observe one of summer’s showpiece objects
M57; the Ring Nebula. This planetary nebula can be seen as a small hazy patch in
14
11
The Sky This Month
small telescopes, larger instruments will show the
‘Smoke Ring’ shape of M57. The Ring Nebula is quite
an easy object to locate, it lies between beta (β) and
gamma (γ) Lyrae, about one third of the way from beta
to gamma.
01 Apr 01:00
15 Apr 00:00
30 Apr 23:00
Another highlight in the constellation of Lyra is the famous ‘Double Double’ epsilon (ε) Lyrae. To the nakedeye epsilon appears to be a single star, however when
viewed through a telescope the star splits into two pairs,
Epsilon1 and Epsilon2. Epsilon 1, the northernmost pair
consists of stars of magnitude +4.7 and +6.2 separated
by 2.6 arcseconds. This is true binary system with the
two stars orbiting each other every 1200 years or so.
Epsilon2 consists of magnitude +5.1 and +5.5 stars
which are separated by 2.3 arcseconds. This is another
binary system with the stars orbiting each other every
585 years.
Low in the north-east you will find Cygnus, which is
also known as the ‘Northern Cross’. At the northern end
of the ‘cross’ lies the constellation’s brightest star alpha
(α) Cygni, Deneb; which forms the western apex of the
‘Summer Triangle’ the other two apexes are marked by
are Vega; alpha (α) Lyrae and Altair; alpha (α) Aquilae.
At the southern end of the ‘cross’, lies Albireo; beta (β)
Cygni, one of the loveliest double stars in the northern
sky. The components of this double have contrasting
colours of golden yellow and blue/green. The brighter
of the two is a magnitude +3.3 K-class yellow giant, it’s
companion is a B-class blue dwarf shining at magnitude
+5.3.
Comet C/2011 L4 Panstarrs should remain visible
throughout the month however it will be fading all the
time as the comet moves further from the Sun (see pages 19 and 20 for more details and a chart of the comets’
predicted location.
12
Chart Produced by
Chris Peat
http://www.heavens-above.coom
13