Download 1” “Sky-Notes” of the Open University Astronomy Club. June 2005. A

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“Sky-Notes” of the Open University Astronomy Club.
June 2005.
A personal message from your scribe.
On 4th June at Ely Cathedral I received my BSc (Hon) in Geosciences. I wish to
express my sincere thanks to Course Teams, Tutors, Fellow Students and friends in
the OUAC who have made this one of the most rewarding experiences of my life. In
particular I would like to thank Bob Lambourne and Barrie Jones who initially
persuaded me to undertake study with the OU and my longstanding friends Tim
Walker and his wife Diane whose encouragement throughout together with that from
members of my family has been second to none.
Normal Service will now be resumed.
All times shown are UT.
1. Solar system.
Earth.
June Solstice on 21d 12h 46m.
The Sun reaches its highest northerly declination.
During the weeks around mid-summer worth scanning the northwestern and northern
deepening twilight sky for the appearance of noctilucent clouds. These form at high
altitude (80km) and appear as luminous bluish clouds well worth capturing on
camera.
Meetings.
Saturday 18th June. 11.00 to 17.00.
Open University Open Day.
Walton Hall.
Milton Keynes.
Saturday 25th June.
BAA Exhibition Meeting.
Cavendish Laboratory.
Madingley Road,
Cambridge.
See BAA website for details. www.britastro.org
Sun.
To prevent permanent damage to your eyes avoid looking at the Sun directly and
never with binoculars or a telescope unless special (expensive!) filters are used. The
safest way is the simplest – project the image of the Sun onto grey or white card.
It is always worthwhile to carry out regular observations for activity.
Moon.
Phases:
New
First quarter
Full
Last quarter
06d
15d
22d
28d
Apsides:
Apogee 11d 06h
Perigee 23d 12h
21h
01h
04h
18h
55m
22m
14m
23m
Diameter. 29’ 28”
Diameter. 33’ 13”
Distance. 405,500km
Distance. 359,700km
Lunar Occultations.
Unlike the gradual disappearance of a planet (small disc) a star vanishes instantly
demonstrating that it is a point source of light as viewed from the earth. For all
occultation events start observing 10 to 15 minutes before the predicted time to
identify the required star and to allow for slightly different time if you are not at
Greenwich. Use an accurate watch to record the time that you observe the occultation
remembering that times are UT not BST. Disappearance is behind the dark limb of the
Moon unless otherwise stated. Enter details in your observing log.
Predictions are for Greenwich, (E 0o.0, N 51o.5) from the BAA Handbook 2005.
Date.
June 16
19
ZC No.
1881
2237
Mag.
Time.
8.5
23h 31.9m
5.1
22h 26.0m
Observing the Moon.
The waxing (evening) and waning (morning) crescent Moon is well placed for
observation from the northern hemisphere observers. Observe along or near to the
terminator where long shadows show greater detail of the Moon’s topography. Use a
basic “Moonmap” to familiarize yourself with the major features i.e. the Maria and
larger craters. Note that the orientation of a feature on a map may differ from that of
the observed image of the Moon depending on the type of telescope used. If you find
the Moon too bright use a filter to reduce the glare. At times features along different
parts of the limb are better presented due the effect of libration – an apparent
wobbling of the Moon about its axis – that allows us to see about 59% of its surface.
The BAA Handbook and some monthly magazines (Sky & Telescope) give details of
the magnitude and direction of libration. The Moon is also an excellent object to start
photography/imaging especially with webcams and digital cameras.
Mercury.
Superior conjunction is reached on June 5th becoming an evening object. By midmonth it should be visible low in the western sky after sunset. A close conjunction
(0.07”) with Venus occurs on the 27th presenting the opportunity to image both
planets in the same field of view. Worth following for a few days either side of the
27th. Magnitude decreases from –1.1 (diameter 5.4”, phase 0.875) on the 14th to 0.0
(diameter 6.7”, phase 0.59) on the 29th.
Venus.
Low down in the evening twilight Venus presents a fairly mundane object at present. .
Magnitude remains at –3.8 with the diameter increasing from10.2” to 11.0” and the
phase decreasing from 0.96 to 0.91 during the month. See note for Mercury regarding
close conjunction.
Mars.
Mars is beginning to become better placed for observation low down in the dawn
skies. During the month brightness increases from +0.3 (diameter 7.8”, phase 0.85) to
+0.0 (diameter 9.2”, phase 0.84). An object for early risers only.
Jupiter.
Moving westwards Jupiter is well placed for evening observation. Unmistakeable at
magnitude –2.2 (diameter 40.4”) fading to –2.1 (diameter 37.0”) during the month.
An excellent target for Webcam imaging. Make the most of the next few weeks as at
next years apparition Jupiter will have a more southerly declination and hence poorer
seeing conditions for northern hemisphere observers. See separate observing sheet.
Use Jupiter to locate gamma Virginis – see separate sheet.
Saturn.
May just be glimpsed low in the northwest evening twilight at the beginning of the
month.
Uranus.
Beginning to emerge into the predawn skies. At magnitude +5.8 it may be located
with binoculars using a suitable starchart.
Neptune.
Further west than Uranus at magnitude +7.9 it may be located with binoculars using a
suitable starchart.
Pluto.
Pluto reaches opposition on June14th. At magnitude 14 it will require at least an 8”
(200mm) diameter telescope and a dark site to locate. Located about two degrees
NNW of xi Serpentis. A suitable target for CCD imaging.
Asteroids.
The following asteroids can be located with binoculars and small telescopes using a
suitable star chart.
Ceres (1). An eighth magnitude object located in Libra. Past opposition (7th May)
Ceres may be located in binoculars using a suitable star chart.
See monthly periodicals/BAA Handbook for details of other asteroids.
Comets.
Comet/2004 Q2 (Machholz). Located in Canes Venatici. Fading to magnitude 11th
this comet is now requires a telescope to observe. Passes close to the galaxy M94
(magnitude 8.2) on June 9th/10th.
Comet 9P/2004 Tempel. A 10th magnitude object beginning to move into twilight.
The target for the Deep Impact mission – July 4th. The impact may cause a rapid
brightening, possibly magnitude 0, but unfortunately the comet will be low in the
evening twilight for observers in the UK. Worth watching just in case!
Up to date details of comets may be found on a number of astronomy web sites such
as the BAA Comet Section web page at www.ast.cam.ac.uk/-jds.
Meteor Showers.
The Ophiuchids are active from May 19th until July with two nights of peak activity
(ZHR 5) on the June 9th and June 19th. Not the most spectacular shower.
Don’t forget the potential spectacle of bright sporadic events. If you are fortunate
enough to observe a very fireball record the time, direction, observed start and finish
points, colour, if fragmenting and any other description. These can then be reported to
a collation point such as the BAA. Analysis of reports may lead to the location of a
“landfall” and possible recovery of meteoritic debris.
Eclipses.
No eclipses this month.
2. Deep Sky.
Abbreviations used.
M = Messier object. (Shown in bold).
NGC = New General Catalogue.
IC = Index Catalogue. (Extension of the NGC).
ds = double star.
ms = multiple star. gc = globular cluster.
oc = open cluster.
pn = planetary nebula. en = emission nebula.
rn = reflection nebula. sg = spiral galaxy.
eg = elliptical galaxy.
lg = lenticular galaxy. ir = irregular galaxy. pg = peculiar galaxy.
snr = super nova remnant.
ly = light year.
The magnitude of an object is shown in brackets e.g. (6.5).
2.1
Variable Stars.
Beta () Persei, Algol. +2.2 to +3.4, period 2.7 days. No favourable evening minima
this month.
Delta () Cephei. +3.5 to +4.4, period 5.37 days. The prototype for the Cepheid class
of variable stars. Their period-luminosity relationship has lead them to being used as
“standard candles” in measuring distances to nearby galaxies.
Maximum brightness occurs on 5th, 10th, 15th, 21st and 26th.
Mu () Cephei. +3.7 to +5.0, approximate period 755 days. A semi-regular variable
star famous for its striking red colour being fittingly called “Herschel’s Garnet Star”.
It is the reddest naked eye star visible from the northern hemisphere. Its colour may
show signs of variability.
To become a regular variable star observer it is advisable to have your own detailed
star charts or those such as available from the Variable Star Section of the BAA. The
Section operates a “mentor” system where novices to variable star observation are
given guidance and support.
2.2
Double Stars/Star Clusters/Nebulae/Galaxies.
The short hours of darkness through the mid-summer months places great limitations
on observations of many deep sky objects.
Bootes (Boo).
Noted for the first magnitude star Arcturus, distinctly orange, which at magnitude 0.04 makes it the fourth brightest star in the sky (Sun excluded).
Some pleasant double stars within the range of binoculars and small telescopes.
Xi () Bootis, 4.9 and 7.0, yellow and reddish purple.
Epsilon () Bootis, 2.5 and 4.9, yellowish orange and blue.
i Bootis, 5.3 and 6.2, yellow and blue.
There are few bright star clusters, galaxies or nebulae to locate.
NGC5466 (9.1) gc. Although fairly large its low surface brightness object makes this
a difficult object in small telescopes. Located 40m east of M3 in Canes Venatici.
NGC5248 (10.2) sg. The brightest galaxy in Bootes. Bright round hub surrounded by
oval haze. Excellent target for large telescopes (12"+) from dark sites.
NGC5660 (11.8) sg. 1o NW of the brighter NGC5676 which should be located first.
NGC5676 (10.9) sg. Bright nucleus surrounded by slight haze.
NGC5669 (11.2) sg. About 1o SE of NGC5676. Barred spiral seen almost edge-on.
Hercules (Her).
NGC6205 (M13) (5.9) gc. Arguably one of the outstanding objects in the northern
hemisphere. Just visible to the naked eye from dark sites it appears as a fuzzy blob in
binoculars. It stands high power well and the outer edges begin to resolve into
individual stars in a 4" (100mm) telescope. Increasing aperture brings greater rewards.
lord Rosse and others using the 72" at Birr Castle in the 19th century observed three
dark rifts radiating from the centre. later visual observers confirmed these. However
with the advent of photography the rifts disappeared. In the 1950's the late Walter
Scott Houston in his "Sky and Telescope" column revised interest in the "propeller".
Responses indicated that visibility of the rifts depended on a careful balance of
aperture and magnification. Today a dark sky is probably a key factor.
NGC6207 (11.6) sg. 40" to the NE of M13 and in the same field as a low power
widefield eyepiece. This moderately bright galaxy is often overlooked due to the
spectacular blaze of the much closer globular cluster.
The area around M13 contains a number of faint galaxies requiring a large (12"+)
telescope to explore. Articles appear from time to time in various publications as an
observer makes initial contact with the area. Identity of the objects can prove
interesting as some are wrongly labelled on some charts/catalogues.
NGC6210 (9.3) pn. Located about 4o NE of  Her.
NGC6229 (9.4) gc. Located about 7o NW of M13.
NGC6341 (M92) (6.5) gc. Slightly fainter and smaller than M13 this globular cluster
deserves equal attention. it starts to resolve in a 6" telescope at high power and
becomes increasingly impressive with increased aperture.
Ursa Major (UMa).
 UMa better known as Mizar, the penultimate bright star in the tail. Closer naked eye
inspection shows that Mizar (2.5) has a fainter companion named Alcor (4.0). The
pair provide a good test for reasonable eyesight. The pair form a optical double ie.
they are not physically associated. Through large binoculars or small telescopes Mizar
itself is shown to have a fourth magnitude companion forming a true binary system.
About 2 SE of  UMa a low power field will reveal two very different deep-sky
objects:
NGC3556 (M108) (10.7) sg. Seen almost edge-on.
NGC3587 (M97) (12.0) pn. The "Owl Nebula". Two dark patches in the ghostly disc
give the distinct impression of two large eyes requiring moderate apertures to see. It is
one of the faintest of the Messier objects.
NGC3992 (M109) (10.6) sg. About a degree SE of  UMa this object is best observed
using high power to remove the bright star (a natural form of light pollution!) out of
the field of view.
NGC5457 (M101) (7.7) sg. About 6o east and slightly north of Mizar. Although large
because it is face-on it has a low surface brightness making observation slightly more
difficult than one might at first expect.
M40 Just over a degree NE of  UMa is a pair of ninth magnitude stars.
Virgo (Vir).
Gamma () Vir. Porrima. ds (3.5/3.5) See separate sheet issued with May “SkyNotes”.
P.V.H.
Useful symbols.
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