April 2009 Observing Guide

Hi all,

April's guide is below:

OBSERVING GUIDE
(Please note all times are BST and are based on an observing location of Belfast and covers the month of April)

The Sun

At the start of the month the Sun rises at 06:55 and sets at 20:00. By the end of the month, it rises at 05:50 and sets at 20.55.

The Planets

Mercury is at greatest eastern elongation on the 26th and will be well placed for observation in the second half of the month. It should be visible from mid-month onwards in the West after sunset. On the evenings of the 27th – 30th, it lies close to M45 – The Pleiades. At month’s end, it sets at 23:05, over two hours after the Sun and is mag +1.0.

Venus is now a morning object but is poorly placed for observation. At month’s end, it rises over an hour after the Sun at 04:40. There is a daylight conjunction between itself and the moon with the details below in the Moon section.

Mars is a morning object this month but is poorly placed for observation.

Jupiter is also a morning object and poorly placed for observation this month. At month’s end, it rises two hours before the Sun at 03:55. As with Venus there is a daylight conjunction with the moon and the details are in the Moon section.

Saturn is the best placed planet this month. It can be located in Leo and rises in daylight hours throughout the month. It sets at 06:45 at the start of the month and by month’s end, it sets at 04:50. It is around mag +0.6 during the month. With the planet’s ring plane almost edge on, this is not a good time to try and observe the rings. It is however a good time to try and observe the smaller satellites and details on the planet’s surface with the rings out of the picture. As with the Earth on the 20th, Saturn will also undergo a similar transition from winter to spring in its Northern Hemisphere on August 10th of this year. However due to the differences between the two planets’ orbits, Saturn will not undergo another equinox until May 2025. The run up to the Saturnian equinox will provide the opportunity to observe interesting events such as conjunctions and transits with its moons. Details of such events can be found below.

Uranus is a morning object this month but is poorly placed for observation.

Neptune is a morning object this month but is poorly placed for observation.


The Moon

The first quarter moon is on the 2nd with the full moon on the 9th. The last quarter moon is on the 17th with the new moon on the 25th.

On the evening of the 1st/morning of the 2nd, a 41% illuminated waxing crescent moon lies close to M35.

On the evening of the 3rd/morning of the 4th, a 67% illuminated waxing gibbous moon lies close to M44 – The Beehive Cluster.

On the evening of the 6th/morning of the 7th, a 92% illuminated waxing gibbous moon lies to the South of Saturn.

During the day of the 19th, there is a conjunction of the moon and Jupiter. The best time to observe it is around midday with the planet lying to the East of a 33% illuminated waning crescent moon. The moon should be visible naked eye, but to observe Jupiter will require the use of binoculars. AS WITH ALL DAYTIME ASTRONOMY, PLEASE BE CAREFUL OF THE SUN.

During the day of the 22nd, there is a conjunction of the moon and Venus. By 14:30 they are less than a degree apart at an altitude of twenty degrees in the South-West. The closest approach between the two is at 16:15 when the pair are half a degree apart. The moon will be in its waning crescent phase with 8% of it illuminated. With a pair of binoculars, this should be visible. AS WITH ALL DAYTIME ASTRONOMY, PLEASE BE CAREFUL OF THE SUN.

On the evening of the 25th, there is chance to observe a 16.5 hour old moon in the West after sunset. Sunset is at 20:45 with the moon hopefully visible half-an-hour later. It sets at 22:05. BE CAREFUL TO ONLY START OBSERVING AFTER THE SUN HAS SET.

On the evening of the 26th, a 4% illuminated waxing crescent moon, Mercury and M45 – The Pleiades form an excellent conjunction in the West after sunset which is at 20:45. The moon should be visible half-an-hour later with the planet lying within two degrees of the lunar crescent. The Pleiades lie within less than a degree of the moon and complete a lovely scene. BE CAREFUL TO ONLY START OBSERVING AFTER THE SUN HAS SET.

Meteors

The ZHR or Zenithal Hourly Rate is the number of meteors an observer would see in one hour under a clear, dark sky with a limiting apparent magnitude of 6.5 and if the radiant of the shower were in the zenith. The rate that can effectively be seen is nearly always lower and decreases as the radiant is closer to the horizon. The Zenith is the overhead point in the sky for an observer. The radiant is the point in the sky, from which (to a planetary observer) meteors appear to originate, i.e. the Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus. A fireball is defined by the International Astronomical Union as a meteor brighter than any of the planets, i.e. magnitude -4 or brighter. The International Meteor Organisation alternatively defines it as a meteor which would have a magnitude of -3 or brighter at the zenith.

There are two showers this month. The first shower is the Virginids which has two peaks. The Alpha Virginids peak on the evening of the 10th and the Gamma Virginids peak on the evening of the 14th. Both have a low ZHR of 5 with neither faring well with lunar conditions. For the Alpha Virginids, there will be major interference with a 1 day past full moon sitting close to Virgo all night. For the Gamma Virginids, conditions are better but still not good, with a 76% illuminated waning gibbous moon rising at 23:00 in Ophiuchus.

The second shower is the Lyrids. They peak during the day on the 22nd at midday. The predicted ZHR is 18, but outbursts have occurred in the past. The radiant is located near to Vega. Although the peak is during the day, you should observe on the evening of the 21st from about 23:00 when the radiant is above the horizon through to dawn on the 22nd. There will be little lunar interference for this shower with a 13% illuminated waning crescent moon rising at 03:15 on the morning of the 22nd. About fifteen percent of Lyrids leave persistent trains and they are typically average speed meteors with rates of 30 miles/second. This is in comparison with the Perseids who have speeds of 42 miles/second.

Comets

Comet/2007 N3 (Lulin) is now past its best and starts the month at roughly mag +9 with it expected to fade as the month progress. It spends the month in Gemini. It sets around 04:00 at the start of the month and by month’s end, it sets around 01:00.

Comet 2006 W3 Christensen lies between the square of Pegasus and Lacerta during the month. It is predicted to remain around mag +10 with long term predictions of mag +8 by the summer months. It is a morning comet and is visible from about 04:00 at the start of the month. By month’s end it is visible from about 02:00.

Comet 67P/Churyumov-Gerasimenko is an evening comet, starting the month in Taurus and moving Eastward into Auriga by month’s end. It is predicted to remain around mag +10 during the month. It sets around midnight throughout the month. It passes close by M45 – The Pleiades around the weekend of 4th/5th and by month’s end; it lies to the South of the mag +1.6 star Beta Tauri (Alnath).

Comet C/2008 T2 (Cardinal) travels through Auriga during the month. It is predicted to be mag +10 at the start of the month and slowly brighten. It sets around 04:00 at the start of the month and by month’s end, it sets at 02:00. On the evening of the 14th at around midnight, the comet passes very close by the open cluster M38. On the evening of the 16th again around midnight, it passes within a degree of NGC 1931 – a mag +11 nebula and open cluster combination similar to the Orion Nebula in character, but much smaller in size. Also on the evening of the 17th again around midnight, it passes very close by another open cluster M36.

Comet Yi-Swan (C/2009 F6) was only discovered last month and is traveling through Cassiopeia toward Perseus. It is circumpolar and visible all night. Current predictions estimate the comet’s brightness at mag +9. On the evening of the 11th, it passes less than a degree South of the mag +2.2 star Alpha Cassiopeiae (Shedar). On the evening of the 23rd/morning of the 24th, it passes a degree South of the Double Cluster (NGC 884 and NGC 869) in Perseus.

Deep Sky

On the deep sky front this month, galaxies M81 and M82 can be observed in Ursa Major. In Leo, we have several galaxies on view including The Leo Triplet - M65, M66 and NGC 3628. M95, M96 and M105 can also be observed in Leo. The place to really find galaxies is in Virgo. The Virgo Super Cluster can be found here with numerous galaxies on view. Also in Virgo, M104 - the Sombrero Galaxy can be found. In Coma Berenices, there is M64 - the Black-Eye Galaxy. Also check out the constellation Canes Venatici with the globular cluster - M3 and several galaxies including M51 - the Whirlpool Galaxy and M63 - the Sunflower Galaxy. In Hercules, two globular clusters – M92 and the excellent M13 can be observed and in Lyra – M57 – The Ring Nebula can be observed. Finally there are some excellent open clusters in Cancer - M44 – The Beehive Cluster and M67.

For further observing information, check out
www.eaas.co.uk/index.php?option=com_cont...=blog&id=6&Itemid=11

General Notes

Always keep an eye out for Aurorae. Check out www.stronge.org.uk/spaceweather.html for the most up-to-date information on the aurorae.

Other interesting naked eye phenomena to look out for include the Zodiacal Light and the Gegenschein. Both are caused by sunlight reflecting off dust particles which are present in the solar system. The Zodiacal Light can be seen in the West after evening twilight has disappeared or in the East before the morning twilight. The best time of year to see the phenomenon is late-Feb to early-April in the evening sky and September/October in the morning sky - it's then that the ecliptic, along which the cone of the zodiacal light lies, is steepest in our skies. The Gegenschein can be seen in the area of the sky opposite the sun. To view either, you must get yourself to a very dark site to cut out the light pollution. When trying to observe either of these phenomena, it is best to do so when the moon is below the horizon. If you are observing them when the moon has risen, restrict your efforts to the period 4 days either side of the new moon as otherwise the moonlight will be sufficient to drown them out.

Finally check out www.heavens-above.com for the latest passes of the International Space Station and satellites, details of Space Shuttle launches and passes and for details of Iridium Flare activity.

Clear Skies

Neill McKeown

Information Sources Used

www.skyviewcafe.com - Used for the Sun and Planets section. Also partly used for the Moon Section

Sky at Night Magazine Observing Guide and CD

www.aerith.net and cometchasing.skyhound.com – Used for the Comet Section for information and finder charts

BAA Handbook

Stardust Magazine

Sky Guide 2009 – South Dublin Astronomical Society

Saturnian Moon Events

Approximate magnitudes of
the listed moons

Mimas +12.9
Enceladus +11.7
Tethys +10.2
Dione +10.4
Rhea +9.7
Titan +8.3
Hyperion +14.2

DATE TIME MOON EVENT
1-Apr-09 01:02 Tethys Moon leaves transit
1-Apr-09 03:37 Dione Moon transits in front of planet
1-Apr-09 03:54 Dione Moon's shadow falls on planet
1-Apr-09 20:46 Tethys Occultation disappearance
1-Apr-09 21:31 Dione+Rhea Conjunction
1-Apr-09 21:39 Enceladus Occultation disappearance
1-Apr-09 23:59 Tethys Eclipse reappearance from Saturn's shadow
2-Apr-09 00:30 Enceladus Eclipse reappearance from Saturn's shadow
2-Apr-09 03:04 Mimas+Tethys+Enceladus Form an equilateral triangle
2-Apr-09 22:19 Tethys Moon leaves transit
3-Apr-09 02:24 Tethys+Enceladus Conjunction
3-Apr-09 21:17 Dione Moon transits in front of planet
3-Apr-09 21:18 Tethys Eclipse reappearance from Saturn's shadow
3-Apr-09 21:37 Dione Moon's shadow falls on planet
3-Apr-09 23:01 Enceladus Moon transits in front of planet
3-Apr-09 23:11 Enceladus Moon's shadow falls on planet
4-Apr-09 00:20 Dione Moon leaves transit
4-Apr-09 00:52 Dione Moon's shadow falls off planet
4-Apr-09 01:35 Enceladus Moon leaves transit
4-Apr-09 01:50 Enceladus Moon's shadow falls off planet
4-Apr-09 20:50 Rhea+Tethys Conjunction
5-Apr-09 00:50 Rhea+Tethys+Dione Conjunction
6-Apr-09 00:17 Enceladus Occultation disappearance
6-Apr-09 03:10 Titan+Dione Conjunction
6-Apr-09 03:11 Enceladus Eclipse reappearance from Saturn's shadow
6-Apr-09 21:53 Rhea Occultation disappearance
7-Apr-09 01:32 Dione+Tethys Conjunction
7-Apr-09 02:13 Rhea Eclipse reappearance from Saturn's shadow
7-Apr-09 20:25 Enceladus+Tethys Conjunction
7-Apr-09 23:53 Dione Occultation disappearance
8-Apr-09 01:39 Enceladus Moon transits in front of planet
8-Apr-09 01:52 Enceladus Moon's shadow falls on planet
8-Apr-09 03:33 Dione Eclipse reappearance from Saturn's shadow
8-Apr-09 20:57 Enceladus Eclipse reappearance from Saturn's shadow
8-Apr-09 23:47 Enceladus+Rhea Conjunction
9-Apr-09 03:05 Dione+Enceladus Conjunction
10-Apr-09 00:15 Mimas+Enceladus Conjunction
10-Apr-09 02:56 Enceladus Occultation disappearance
10-Apr-09 21:15 Dione Eclipse reappearance from Saturn's shadow
10-Apr-09 21:59 Enceladus Moon leaves transit
11-Apr-09 01:07 Mimas+Enceladus Conjunction
11-Apr-09 02:42 Enceladus+Tethys Conjunction
11-Apr-09 20:15 Tethys+Dione+Enceladus+Rhea Kite shaped conjunction
11-Apr-09 20:39 Dione+Enceladus Conjunction
11-Apr-09 21:44 Tethys+Rhea Conjunction
12-Apr-09 02:18 Dione Moon transits in front of planet
12-Apr-09 02:44 Dione Moon's shadow falls on planet
12-Apr-09 20:42 Enceladus Occultation disappearance
12-Apr-09 20:44 Tethys+Hyperion Conjunction
12-Apr-09 23:37 Enceladus Eclipse reappearance from Saturn's shadow
13-Apr-09 00:37 Enceladus+Titan Conjunction
13-Apr-09 20:45 Tethys+Dione Conjunction
13-Apr-09 20:56 Rhea Moon's shadow falls off planet
14-Apr-09 01:06 Rhea+Enceladus Conjunction
14-Apr-09 20:25 Dione Moon's shadow falls on planet
14-Apr-09 22:04 Enceladus Moon transits in front of planet
14-Apr-09 22:58 Dione Moon leaves transit
14-Apr-09 23:42 Dione Moon's shadow falls off planet
15-Apr-09 00:31 Dione+Tethys Conjunction
15-Apr-09 00:38 Enceladus Moon leaves transit
15-Apr-09 01:52 Tethys Occultation disappearance
15-Apr-09 20:45 Tethys+Enceladus Conjunction
15-Apr-09 21:10 Mimas+Rhea Conjunction
15-Apr-09 22:39 Rhea Occultation disappearance
16-Apr-09 00:31 Tethys Moon transits in front of planet
16-Apr-09 03:10 Rhea Eclipse reappearance from Saturn's shadow
16-Apr-09 23:10 Tethys Occultation disappearance
16-Apr-09 23:20 Enceladus Occultation disappearance
17-Apr-09 02:18 Enceladus Eclipse reappearance from Saturn's shadow
17-Apr-09 02:32 Tethys Eclipse reappearance from Saturn's shadow
17-Apr-09 21:48 Tethys Moon transits in front of planet
18-Apr-09 00:42 Tethys Moon leaves transit
18-Apr-09 22:21 Enceladus+Mimas Conjunction
18-Apr-09 22:35 Dione Occultation disappearance
18-Apr-09 23:52 Tethys Eclipse reappearance from Saturn's shadow
19-Apr-09 00:02 Tethys+Enceladus Conjunction
19-Apr-09 00:43 Enceladus Moon transits in front of planet
19-Apr-09 02:22 Dione Eclipse reappearance from Saturn's shadow
19-Apr-09 02:22 Mimas+Tethys Conjunction
19-Apr-09 20:05 Enceladus Eclipse reappearance from Saturn's shadow
19-Apr-09 21:59 Tethys Moon leaves transit
19-Apr-09 23:13 Mimas+Enceladus Conjunction
20-Apr-09 01:46 Dione+Enceladus Conjunction
20-Apr-09 21:11 Tethys Eclipse reappearance from Saturn's shadow
20-Apr-09 23:36 Tethys+Mimas Conjunction
21-Apr-09 00:46 Enceladus+Titan Conjunction
21-Apr-09 02:00 Enceladus Occultation disappearance
21-Apr-09 21:02 Enceladus Moon leaves transit
21-Apr-09 22:26 Mimas+Dione Conjunction
22-Apr-09 20:53 Mimas+Tethys Conjunction
22-Apr-09 21:14 Tethys+Dione Conjunction
22-Apr-09 21:52 Rhea Moon's shadow falls off planet
22-Apr-09 22:31 Enceladus+Tethys Conjunction
23-Apr-09 01:00 Dione Moon transits in front of planet
23-Apr-09 01:31 Dione Moon's shadow falls on planet
23-Apr-09 22:45 Enceladus Eclipse reappearance from Saturn's shadow
24-Apr-09 02:02 Tethys+Dione Conjunction
24-Apr-09 23:27 Rhea Occultation disappearance
25-Apr-09 02:00 Mimas+Enceladus Conjunction
25-Apr-09 21:08 Enceladus Moon transits in front of planet
25-Apr-09 21:37 Dione Moon leaves transit
25-Apr-09 22:33 Dione Moon's shadow falls off planet
25-Apr-09 23:41 Enceladus Moon leaves transit
26-Apr-09 01:01 Dione+Mimas Conjunction
26-Apr-09 21:11 Tethys+Rhea Conjunction
26-Apr-09 23:03 Rhea+Enceladus Conjunction
26-Apr-09 23:59 Mimas+Dione Conjunction
27-Apr-09 22:25 Enceladus Occultation disappearance
28-Apr-09 01:26 Enceladus Eclipse reappearance from Saturn's shadow
29-Apr-09 01:24 Dione+Rhea Conjunction
29-Apr-09 21:18 Dione Occultation disappearance
29-Apr-09 23:46 Enceladus Moon transits in front of planet
30-Apr-09 01:12 Dione Eclipse reappearance from Saturn's shadow
30-Apr-09 22:51 Tethys+Enceladus Conjunction

Clear Skies

Neill

Thanks for that Neill,

Michael.

Great stuff Neill.

Just wondering, do you have access to the calendar section of the site?
If so, it would be great if some of these events could be incorporated into the ncalendar so that we are reminded of them.
If you don't have access to upload details but are willing to do so, let us know and we'll amend your user profile.

Michael.

Hi Michael,

I do access to update the calendar, so will put a few of the events on it.

Neill

Hi Michael,

Tried to add something to the calendar, but unable to. My user settings must not be set up to do so.

Neill

Guide updated for new comet - Yi-Swan (C/2009 F6).

Neill