WA Newsletter, February 2017 by Brian Halls

The Southern Astronomer No.101 â&#x20AC;&#x201C; February 2017

SOUTHERN ASTRONOMER THE

MONTHLY MAGAZINE OF WORTHING ASTRONOMERS & WORTHING SKYWATCHERS

THE MARE CRISIUM

The Southern Astronomer No.101 – February 2017

WORTHING ASTRONOMERS No fees, no Committee; just enjoying the night sky together.

ormed in 2008 by a group of regular and practical observers, Worthing Astronomers is a free to join society now with a membership of over 450 persons, who have a common interest in Astronomy and its associated subjects – no internal politics, no fees, no committees, just astronomy!

The Southern Astronomer This Issue Astronomy This Month The Planets in February Workshop Night The Eye of the Man in the Moon The Night Sky

Our aim is simple – to bring astronomy to the public in general and to help and assist our membership in observing the night sky. With the aid of this newsletter, website, social media, regular star parties, workshops and public observing events we hope to encourage and share our interests in observing the sky with the public, our colleagues in our own group and with those of neighbouring astronomical societies.

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Cover Pictures & Comment Normally we would be looking forward to our February Workshop meeting but this has had to be cancelled. Page 5 of this issue will tell you of the alternative event for that evening – a group observing event at Goring Gap, details in the article.

We try and meet at least once a month (when weather conditions allow) to do some observing but at the moment we do hold, every two months, a Workshop evening when we get a chance to meet up, exchange ideas and tips and help each other to make the most of observing the sky above us. Occasionally a guest speaker will talk about an aspect of practical, hands on astronomical observing.

Setting up on the Friday evening of the Workshop takes a certain amount of time and actually working out a programme for that evening as well as presenting it is time consuming especially as the workload for much of that evening is placed on too few shoulders.

These Workshop evenings are held on the first Friday of every other month (April, June, August, October and, December) at Goring Methodist Church Hall, Bury Drive (off of Aldsworth Avenue), Worthing, BN12 4XB. The admission charge of £3 helps pay for the room and free refreshments and goes towards supporting our membership. Doors open at 7.00 pm with the meeting starting at 7.30.

If the Workshops are to proceed for the rest of the year, a volunteer team is needed. ** There is an unusual lunar eclipse on the night of 10/11 February. The Moon passes through the outer shadow of the Earth that is cast into space by the light of the Sun. A late night for some if the clouds stay away.

We can be found at: worthingastronomers.org.uk

On the subject of things lunar, one of the earliest glimpses of the Moon we get to see in the evening sky is that of a dark round plain – the Mare Crisium (Sea of Crises). Even a small telescope will show some of the finer features while larger instruments will highlight some of the more subtle. A guide to this fascinating lunar feature is on page 6.

There are several astronomical groups in the coastal area of Sussex - several WA members are also members of the Adur Astronomical Society, who meet every first Monday of the month for a lecture regarding an astronomical subject. Details for the AAS can be found at Adur Astronomical Society.

Cover Image: 2015 April 23 © Brian Halls

CONTRIBUTIONS AND UNSUBSCRIBING Contributions – written articles (word processed in .txt, .doc or .odt format), photographs, letters, advertising copy to the editor for the March issue should be in by February 15 and sent to the editor at the contact address: editor@worthingastronomers.org.uk

Contact addresses: Acting joint coordinators - info@worthingastronomers.org.uk – general society details, Janet Halls or Brian Halls treasurer@worthingastronomers.org.uk – donations contact Janet Halls acting-treasurer.

If you no longer wish to subscribe to the group and cancel newsletters and other information, please send an email to: info@worthingastronomers.org.uk with 'Unsubscribe' in the subject line; we do not want our stuff to end up like spam littering your inbox.

outreach@worthingastronomers.org.uk – events contact Steve Bassett, Mike Williams website@worthingastronomers.org.uk – contact for website Perry Wilkins

Volunteers are always welcome: if you want to find out more, call 01903 521205 or drop us a line at the e-mail address above.

editor@worthingastronomers.org.uk – newsletter content detail Brian Halls

If you like the newsletter or its content please feel free to distribute it to anyone you know who might be interested. Content is subject to copyright to the group and/or the individuals whose images or articles are used.

The Southern Astronomer No.101 – February 2017 FEBRUARY LUNAR PHASES

ASTRONOMY

THIS MONTH

February 2017

All times are expressed as Universal Time (UTC – Co-ordinated Universal Time) and can be considered the same as GMT (Winter Time) Information given, unless otherwise stated is for the 15th of the month at 21.30h. Lunar and other phenomena in the Quick View Diary are shown to the nearest hour. This is still the season for cold, clear (and frosty) nights which generally give good seeing. Frost can occur and it is not unknown to scrape it off of ones telescope tube during an observing session! Yet, if you are well wrapped against the cold, observing under these conditions can be a pleasure. An unusual penumbral eclipse of the Moon occurs on the early hours of the 11th. By the start of the month. The Sun is rising nearly half an hour earlier and setting nearly an hour later than it was a month ago and by the end of the month, these times will have increased further.

QUICK VIEW DIARY D UT 1 Sunrise 07.39; Sunset 16.55 3 Equipment Clinic & Lunar X at Goring Gap from 7.30 p.m 4 04h Moon: FIRST QUARTER 11h Moon rise 5 21h Aldebaran 0.3°S of Moon 6 13h Moon at perigee (closest to earth in its orbit) 10 17h Moon Rise 11 01h FULL MOON and eclipse 18 01h Moon rise 20h Moon: LAST QUARTER 21h Moon at apogee (furthest from earth in its orbit) 26 07h Moon rise 14h NEW MOON 28 Sunrise 06.49; Sunset 17.43

However, the diameter of the Moon and the width of the penumbra are not exactly the same size, at times the Moon will be dimmed overall with brightening at the south or north pole while at the other pole it might take on a little darkening as the Moon just clips the darker shadow of the umbra. If the clouds keep away on that early Saturday morning we might just see a little darkening towards the Moon’s northern limb (edge) at mid eclipse (as can be seen from the graphic on the left.) Times for this eclipse are as follows: First contact {1} 22:34:16 UT (February 10) Greatest Eclipse 00:34:01 UT Last contact {7} 02:53:26 UT At the time of mid-eclipse, the Moon will be reasonably high and will be just east of the local meridian. As this occurs late Friday evening and early on Saturday morning some of us who do not have to get up too early that morning may be able to take advantage of the late night to see how the eclipse appears.

OBSERVING

THIS MONTH

Penumbral eclipse February 11

LUNAR ECLIPSE Just after 0h on February 11, the Moon will pass through the outer shadow of the Earth thrown into space by the light of the Sun.

stronomical events like this months lunar eclipse and the positions of the planets can be calculated with high precision hundreds and even tens of thousands of years in advance.

The position of the Sun in the sky is similar; we know where it will This outer shadow is called the penumbra and this type of eclipse is be in relation to the back ground stars also with great accuracy. The called (not surprisingly) a penumbral lunar eclipse. one thing we cannot know about the Sun is what activity it will show us. These type of eclipses are not as colourful or dramatic as a total lunar eclipse when the Moon passes through the darkest part of the We know that there is a regular sunspot cycle that we are living Earths shadow – like the event of late September, 2015. through at the current epoch – sunspot activity is at a minimum

The Southern Astronomer No.101 – February 2017 and over the period of 4-5 year this activity increases, reaches a maximum and over a 5-6 year period sunspot activity slows down and decreases before the cycle starts all over again. Sunspots are caused by solar magnetic fields distorting and twisting and which break through the Sun’s visible ‘face’ - the photosphere. At this moment (and following a pattern of the last few years or so), the Sun’s magnetic fields are not as vibrant as one might expect. This has resulted in the last few years of low sunspot activity. Sunspot activity has remained low with January being ‘quiet’. Many of the sunspots visible are small or in the case of sunspot groups, not large or active. In December Brian States observed the Sun on 19 days with several days being recorded as spotless. There were one or two moderate sized groups visible in the month (right.)

AR 2615, December 4 © Brian Halls

Moon when seen from the eclipse track.

One sure fire prediction about the Sun this month is that there will be an eclipse of the Sun on February 26, It will be an annular eclipse which means the angular diameter of the body of the New Moon is slightly smaller than the angular diameter of the Sun, this will cause a ring of sunlight to appear around the silhouette of the body of the

Unfortunately for us, this event can only be seen from the southern Atlantic Ocean. From the Falkland Islands the Sun will be 80% eclipsed as they lay just south of the track.

The appearance of the planets in February

or all of the month the innermost planet Mercury will be a morning object. At the start of February the planet will be rising just under an hour before the Sun and will be the best time to see the elusive planet; by the end of the month the time

OBSERVING THE PLANETS

IN FEBRUARY 4

The Southern Astronomer No.101 – February 2017 difference between sunrise and planet rise will be only a matter of minutes. A good eastern view of the sky will be required to see the planet at the start of the month.

TRUE BLUE? Some people have eyesight that has a sensitivity towards the blue/UV end of the spectrum and might be able to make out Venusian cloud details better than others.

The second planet out from the Sun, Venus, is now high and prominent in the evening sky. Now past dichotomy (half phase) the angular diameter of the planet gets larger as the phase decreases. This really is a good time to observe the planet – ideally while it is in the twilight sky and the glare from the planet does not obscure the faint cloud markings often seen on the disk.

Some years ago, several members of the British Astronomical Association (BAA) had their eyesight tested and it was found that one or two of them had this slight ability. Patrick Moore – an avid Venus observer – was one of those who took part in the test and found much to his chagrin that his eyesight was not shifted towards the blue/UV. That Patrick was able on occasions make out cloud features on Venus shows that they are viewable by anyone when telescope resolving power, conditions and, tenacity of the observer allow.

It is often mentioned that a yellow filter (Wratten 15 grade) is useful for observing either visually or with some form of imaging to bring out detail. I have often found a light blue filter (80B) useful for enhancing cloud features of the planet.

Though it rises late evening at the start of the month– 23.18UT on the 1st it rapidly progresses as the month passes by - 22.26UT on the 14th and 21.27UT on the 28th.

If you are really lucky to have a UV filter (320-400nm) then this will really enhance views of the Venusian cloud system if using some Saturn is a bright star dominating the early morning skies. Mid form of mono-photography/imaging. These UV filters are no good for month it rises at 04.02UT so it is still an object for those night owls visual observing due to the sensitivity of the human eye. or early birds among us. Moving on from Venus and to the outermost of the terrestrial planets, Mars. As can be seen from the schematic on the previous page, This planets angular diameter when viewed through a telescope is no larger than that of Mercury. Mid-February the planet is in the west after sunset and follows the Sun down some four hours later.

Uranus and Neptune the outermost major planets of the solar system are visible in the evening skies as a small green disk and blue disk respectively. When capturing a view of Uranus it is interesting to realise that we are looking on one of its poles rather than an equatorial view as we get from the rest of the planets due to a skewered rotation. What caused this no one knows though it is suspected that at some time during the early formation of the solar system, something large whacked into the planet causing its tilt to get well away from the perpendicular.

It does not seem all that long ago that Jupiter slipped away from our evening skies but now it is returning.

Planets mid month

WORKSHOP NIGHT

s most will be aware, the February Workshop Clinic at our usual venue has had to be canceled due to circumstances.

Ideally there must be a second person at the door to help and assist with questions for newcomers.

As an alternative, a Clinic and Lunar X observing session will be held at Goring Gap from 7.30 p.m. For contact details regarding this evening contact Graham Williams at grahamjw47@gmail.com. The evening going ahead will be dependent on weather conditions.

The refreshments have to be set up – a job that has been undertaken so well by Chris Pennells who I regret to say has had to stand down from this role due to health reasons. Many, many thanks for his time and service.

Not a lot of people probably realise the amount of time and effort that goes into organising the Workshops.

The meeting itself takes some organising. What subjects are going to be covered; who are those speaking?

At ground level, we have to get access by 6.45 so the chairs, tables, projector stand, projector and laptop have to be set up. The Treasurer has to be in place to take the entrance fees and ensure that those coming in also sign in which is for fire and accident safety reasons.

From February this work load was going to be down to two people. We need volunteers! If the meetings are going to proceed during 2017 we shall need commitment from the membership in the way of help and assistance. The future of the Workshops is in your hands.

The Southern Astronomer No.101 – February 2017

THE EYE OF THE MAN IN THE MOON The Mare Crisium The terms ‘east’ and ‘west’ on older lunar maps are different to a modern lunar map. They were inverted during the 1960’s . The images in this article show south up, north down and east to the left ( i.e – preceding limb or standard astronomical telescope view) and follow the modern IAU convention.

ook up at the young crescent Moon in the early evening at January’s end or at the start of February a distinctive feature that can be seen with the unaided eye is a circular object called, the Mare Crisium – the Sea of Crises. Billions of years ago when the solar system was being formed a large object struck the Moon and created a giant crater that would become known as the Mare Crisium. It must have been some object as spacecraft ‘wobble’ in their orbit when passing over the feature. These wobbles – there are other areas of Moon that cause them are called mascons for mass concentrations.1 Binoculars will show the broken outline of lunar features around the ‘shore’ of the 600 km diameter sea while a small telescope will show large craters on the lava plain. Large ‘scopes will show finer detail and pick up many smaller craters and features. It must have been quite a spectacular crater but this impact and others caused lava to well up and flow across the floor of the crater hiding it for ever. The area was bombarded by impacts and some these in turn were obliterated by later impacts that caused lava flows to flood or partly obscure them. We can still see evidence of this today when we look through the telescope eyepiece and are described further on. Mare Crisium, 2017 January 2

It is always a good idea to have a chart to use as a guide when looking through the telescope eyepiece such as Peter Grego’s which available to download free.2 H P Wilkins in his book The Moon, dedicated the best part of two and a half pages of description to the Mare itself with further detailed descriptions of the features elsewhere – I will be less detailed and leave it to view for yourselves. There are two large craters on the Crisium basin, Peirce in the north-west and Picard to the south-west of Crisium. Picard is the largest crater at 23km. There is some terracing to the crater walls. Peirce is 19km with walls rising to about 2000m. To the east of Picard is a small craterlet which can be seen in when light and shadow are just right. Bright material can be seen around this small crater with a moderate magnification. To the north-west of Picard are the remains of crater, Yerkes which has filled with lava at sometime in its past. This can be seen well in the image on the front cover. Keeping with partly filled craters being named after famous US observatories, is another filled crater, Lick. It is larger than Yerkes. A small telescope will show its eastern wall when the terminator is just to the west – when the Moon is about four days old. To the south-east, Crisium’s plain is broken into by upland material which forms the Prom Agarum. ‘Mist’ like appearances have been observed near the Prom when the area is undergoing sunrise

Peter Grego’s chart of the eastern limb of the Moon

The Southern Astronomer No.101 – February 2017 conditions. This is likely to be due to a high area on the mare being caught by the rising Sun for a small time – certainly not due to water vapour! The floor of Crisium also has a number of features called dorsa or wrinkle ridges – crossing its floor. The ridges are the uneven boundaries likely caused by the various flows of lava across the plains at differing times. Around the mare are a selection of interesting objects. To the north is the large 126km crater called Cleomedes. There are two small craters on the southern area of its floor and a range of hills just north of centre. To the north is a rille that branches in two. This can be seen in a 100mm telescope. To the west, in the brighter uplands is a ray feature, Proclus. This crater is very bright when compared with the surrounding lunar uplands – it is secondary only to Aristarchus - and as the Moon Crisium seen at its best © Chris Pennells progresses to Full a distinctive ray system can be seen coming from it. Good seeing and a reasonable magnification show the crater Another interesting feature on the western borders of the Crisium outline to be polygonal in shape (picture below, crater bottom right.) plain is a feature that looks a little like a bay enclosed by to → promontories (picture centre left). ---------------------------------------------------------------------------------------Top left of the picture is Picard; just above centre is the ‘ghost’ crater Yerkes. Just lower right of centre is the ‘bay’. The upper (south) promontory is Prom Lavinium and the northern (lower feature) is Prom Olivium. The story of O’Neill’s Bridge has appeared in the newsletter before but for new members I will just touch on the story again. In the summer of 1953, John O’Neill was observing the Olivium/ Lavinium gap with his 100mm telescope in New York the Moon which was two days past Full. He saw, what he thought was a fan shaped light broken by a shadow of an arch – as one would might see sunlight shining under a bridge span with the shadow of the bridge silhouetted against it. He wrote to the foremost amateur lunar observer of the day, H P Wilkins in the UK, who when the Moon was again just passed Full, observed the area and saw the same fan of light. Several observers saw it though were not necessarily convinced that it was a bridge like feature on the Moon. ←