1” “Sky-Notes” of the Open University Astronomy Club. May 2006



Дата24.04.2016
Памер30.4 Kb.
#24528
“ > 1”
Sky-Notes” of the Open University Astronomy Club.
May 2006.

1. Solar system.
Note that all times shown are UT, remember to adjust for BST as necessary.
Earth.

From late May to July it is 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 20th May. BAA Instruments & Imaging Section Meeting, The Humfrey Rooms, Castilian Terrace, Northampton. Doors open 09.30. Meeting starts 11.00. Admission £5 includes lunch and other refreshments.
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.


Although approaching the minimum of the current solar cycle it is always worthwhile to carry out regular observations for activity. Current active sunspot group (875).

See www.spaceweather.com for up to date information of solar activity and related events. Decreasing hours of darkness limit the opportunity for observing aurora.


Moon.

Phases:

First quarter 05d 05h 13m

Full 13d 06h 51m

Last quarter 20d 09h 21m

New 27d 05h 26m
Apsides: Apogee 07d 07h Diameter. 29’ 32” Distance. 404,569km.

Perigee 22d 15h Diameter. 32’ 25” Distance. 368,612km.



Moon continued.

Spring evenings provide the opportunity to observe (at social hours for many) the waxing crescent Moon from thin crescent through first quarter. Observe the regions along the terminator (sunrise on the Moon) where the low angle of the Sun highlights lunar topography. A basic lunar map is all you need to get started. If you are starting out on photography and/or imaging the Moon will provide an excellent target.



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. ZC No. Mag. Time.

May. 02 1088 5.6 21h 41.2m

08 1716 6.4 21h 05.7m

29 1042 6.6 21h 19.6m
Mercury.

Unlikely to be seen very low in the bright dawn SE sky. Superior conjunction is reached on 18th May. Watch for its appearance in the NW evening sky at the end of the month. Magnitude –1.1, phase 0.85 on 30th May.


Venus.

At magnitude –4.0 fading to –3.9 during the month Venus should be spotted very low in the SE dawn skies. The diameter decreases from 17” (phase 0.65) to 14” (phase 0.75) during the month.


Mars.

An evening object in Gemini. Magnitude fades from +1.4 to +1.7 and decreases in size (5.0” to 4.4”) during the month as the Earth – Mars distance increases. The planet presents a distinct gibbous phase of about 0.94 but the small disc will now require moderate or larger aperture telescopes to observe detail.


Jupiter.

Opposition is reached on 4th May providing nightlong observation. Brilliant at magnitude –2.4 with the diameter of over 44”. Try locating the new “Little Red Spot”. The current low declination will adversely affect seeing conditions for observers in the northern hemisphere. Jupiter is an excellent target for Webcam imaging. See separate observing sheet for Jupiter and Saturn.



Saturn.

Sinking into the western sky Saturn is still well placed for evening observation. Located just west of the star cluster M44 Praesepe in Cancer making an attractive view in binoculars and low power on small telescopes. Brightness fades slightly from +0.2 (diameter 16.5”) to +0.3 (diameter 17.2”) during the month. Saturn is an excellent target for Webcam imaging. See separate observing sheet.

The Cassini spaceprobe continues to return staggering images and data of the planet and its extensive satellite system. The NASA website warrants a daily visit at: http://saturn.jpl.nasa.gov and http://ciclops.org
Uranus.

A 6th magnitude object located in Aquarius visible in the SE predawn sky.


Neptune.

An 8th magnitude object located in Capricornus visible in the SE predawn sky.


Pluto.

A 14th magnitude object located in Serpens Cauda. Opposition is reaches on 16th June. It will require a large aperture telescope to observe visually. Good CCD target.


Asteroids.

The following asteroid can be located with binoculars and small telescopes using a suitable star chart.



Vesta (4). A 9th magnitude object located in Gemini. Fading slowly.

See monthly periodicals/BAA Handbook for details of other asteroids.


Comets.

Comet 73P/Schwassmann-Wachmann. A small fragmented comet due to make a “close” approach to the Earth during May. Visible in binoculars at the end of April and brightening so will become a naked eye object from dark sites. Moonlight will increasingly interfere especially (Full Moon on 13th) when the comet is at its brightest around 11th –16th May. It will be worth following May and early June as it moves rapidly across the sky. On the 8th fragment C passes close to M57, The Ring Nebula, in Lyra that will be well worth imaging in dark skies just before dawn from the UK. Recent Hubble HST images show that the comet is continuing to break up. Preliminary data for fragments B, C and E are giving in the BAA handbook although magnitudes are uncertain. See BAA Comet Section webpage www.ast.cam.ac.uk/-jds for updates and data for other comets.
Meteor Showers.

The Aquarids are active between 24th April – 20th May. Maximum activity occurs on the 4th with a ZHR of about 40.

Don’t forget sporadic events and the chance of a brilliant fireball. The latter should be recorded and reported.
Eclipses.

No eclipses this month.

See the club website for reports of the 29th March Total Solar Eclipse.

Observing Jupiter & Saturn.
Keep for future reference.
Jupiter. The disc appears distinctly flattened - equatorial diameter greater than the polar diameter. The equatorial bulge is due to Jupiter's very rapid rotation of under 10 hours. Even a short observing session of half an hour will show the rapid rotation of surface features. The main cloud belts are easily seen in small telescopes and with increasing aperture and magnification more and more detail is revealed, subject to atmospheric conditions. Watch for the Great Red Spot, smaller white spots, belt detail, satellite shadows etc. Use as high a magnification as seeing conditions allow. The use of coloured filters can enhance features. Try a selection and you will be surprised at their effect.

Following the ever-changing pattern of the four Galilean satellites - Io, Europa, Callisto and Ganymede - is a fascinating exercise over a few hours and subsequent evenings. Plot your observations on a sheet of graph paper and you will produce their orbital patterns. Identifying each of the satellites is straight forward using charts such as those printed in the BAA Handbook or periodicals such as Astronomy Now, Sky and Telescope, etc.


Saturn. The Cassini division in the rings should be easily seen. Moderate apertures and high power may reveal the Encke division and the dusky Crepe ring, seeing conditions allowing. Cloud belts are visible but these are much less prominent than those on Jupiter. On rare occasions large storm systems may be visible as white spots and/or patches. The use of colour filters enhances the detail.

Saturn's largest satellite, Titan (8.3), is easily visible and moderate aperture telescopes should reveal six others: Mimas (12.9), Enceladus (11.7), Tethys (10.2), Dione (10.4), Rhea (9.7), Iapetus (10.2 - 11.9). Iapetus shows decided variations in brightness, probably due to surface features, with western elongations being brighter than eastern elongations. A suitable chart will be necessary to avoid confusion with faint background stars. The BAA Handbook contains charts for Titan and Iapetus and data for the others. Astronomy Now gives a chart for Titan.

Having identified the brighter satellites visually visit the Cassini mission web site to see what remarkable objects these small specks of light really are and the fascinating planet and ring system they inhabit. See http://saturn.jpl.nasa.gov and http://ciclops.org
Photography/CCD/Webcam Imaging of Jupiter and Saturn.

The brightness and large disc size of these planets make them excellent targets for the aspiring and experienced astrophotographer/CCD/webcam imager.

A wide angle, unguided exposure of up to 25 seconds on ASA 200 or 400 slide film will record the planet amongst the background stars of the constellation through which the planet is currently passing.

The main barrier to recording “surface” details will be the prevailing seeing conditions but with patience and a little luck excellent results can be achieved.

There are a number of publications on photography and imaging to which you can refer to as necessary.

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).





    1. Recent and current events.

Active galaxy OJ+287 in Cancer. A BL Lac object which may be on the verge of its regular outburst. Requires regular monitoring with reports being submitted to the BAA Variable Star Section. Good ongoing project for the 16”.

Gamma Virginis. This interesting binary is best placed for observation from late evening through the early hours star. Now past periastron it should be possible to split visually with the 16” under good seeing conditions and worth trying with smaller apertures to record when it can be resolved. Another object that requires regular monitoring over the next months. The unexpected motion detected at the last periastron passage in the 1930’s has again been observed indicating the presence of an unseen companion in the system, hence the need for continuing observations.


    1. Variable Stars.

Beta () Persei, Algol. +2.2 to +3.4, period 2.7 days. Although low in the north suitable evening minima occur on 20d 23.4h and 23d 20.2h.

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 very successful “mentor” system where novices to variable star observation are given guidance and support.

2.3 Double Stars/Star Clusters/Nebulae/Galaxies.
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. Locate M3 in Canes Venatici and move 40m east

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.


Canes Venatici (CVn).

 CVn ds, (2.9,5.5) separation 19.6". Cor Coroli (Heart of Charles), A fine bluish-white and white double star.

NGC4151 (11.2) sg. Barred spiral with a bright nucleus.

NGC4215 (10.5) ir. Located south and slightly west of NGC4244.

NGC4244 (10.7) sg. Spiral galaxy seen edge-on appearing as a needle of faint light. Fine object whose appearance brightens with increasing aperture.

NGC4258 (M106) (8.3) sg. Large inclined galaxy located about 5o east of UMa on the borders of Canes Venatici and Ursa Major.

NGC4395 (11.0) sg. Bright core with a low surface brightness circular halo.

NGC4449 (10.5) ir. Appears almost rectangular making it an unusual object to view.

NGC4485 (12.5) ir and NGC4490 (10.1) sg. Interacting pair of galaxies.

NGC4631 (9.7) sg and NG4656 (10.4) pc. are a fine example of a pair of interacting galaxies, both edge-on to our view, located mid-way between Cor Coroli and the Coma star cluster. One end of NGC4656 has a distinct hook which may be glimpsed in 8" telescopes under good seeing conditions.

NGC4736 (M94) (8.2) sg. Locate B CVn and move 3o east to locate the tightly wound spiral galaxy which has a very bright core. 16" (40cm) telescopes reveal a hazy ring infilled with dusky mottling surrounding the core.

NGC5005 (10.8) sg. Located to the SE of  CVn.

NGC5033 (11.0) sg. Appears in the same low power wide field as NGC5005.

NGC5055 (M63) (8.6) sg. Easily located 5o east and slightly north of M94. Oval patch with brighter core.

NGC5194 (M51) (8.4), sg and NGC5195 (9.3). Interacting pair of galaxies. Aptly named the Whirlpool galaxy M51 was the first galaxy to have its spiral structure recognized. (Lord Rosse 1845). To locate the pair use the bright star  UMa at the end of the Plough and move about 4o SW. Both objects are easily visible in binoculars. A 12" (30cm) telescope will begin to show the subtle spiral structure and the tenuous bridge between the two galaxies.

Canes Venatici continued.

NGC5272 (M3) (6.4) gc. Superb globular cluster easily seen as a fuzzy spot in binoculars. 12" telescopes will almost resolve this cluster to its core. To locate move about half the distance between Cor Coroli and the first magnitude star Arcturus (0.0). A fine end to your tour of this constellation.


Corona Borealis (Cor).

An easily recognized attractive circlet of moderately bright stars. It is one of the few patterns which span many cultures in virtually the same form. Worthy of a camera shot.

Two objects of interest are the variable stars R CrB and T CrB.

R CrB is normally around 6th magnitude remaining almost constant for even periods of years. However it can abruptly plunge to 14th or 15th magnitude and then slowly recover to the norm, often with "relapses". Well worth a nightly check.

T CrB is a recurrent nova. Normally about 10th magnitude it can suddenly brighten without warning and reach magnitude 2 or 3 as in 1866 and 1946. Lesser "outbursts" occurred in 1963 and 1975. Another object that is well worth monitoring.

Abell 2065 Galaxy Cluster. R.A. 15h 22.7m. Dec. +27o 43’. Included as a target for 16” imaging.


Draco (Dra).

The following are located close to the northern border of Bootes.

NGC5866 (10.0) eg. Once thought to be one of the missing Messier objects (M102).

NGC5879 (11.5) sg. Faint elongated streak of light brightening towards the centre.

NGC5907 (10.4) sg. A fine example of a spiral galaxy seen almost edge-on. Thin needle of light with a bright core. Larger scopes will show a dark dust lane along its western edge.
Ursa Major (UMa).

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.

P.V.H.
Useful symbols.



o b


Поделитесь с Вашими друзьями:




База данных защищена авторским правом ©shkola.of.by 2022
звярнуцца да адміністрацыі

    Галоўная старонка