RASNZ Electronic Newsletter September 2015

The RASNZ Email newsletter is distributed by email on or near the 20th of each month. If you would like to be on the circulation list This email address is being protected from spambots. You need JavaScript enabled to view it. for a copy. The latest issue is below.

Email Newsletter Number 177

Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website http://www.rasnz.org.nz/ in their own newsletters provided an acknowledgement of the source is also included.


1. Colin Keay 1930-2015
2. Auckland Ast Soc's Burbidge Dinner - Oct. 3
3. Aoraki Mackenzie Starlight Festival - Oct. 9-11
4. Astrophotography Weekend - Foxton Beach, Nov. 13-15
5. Stardate 2016 - Wairarapa, January 8-10
6. Central Star Party - Hawkes Bay, January 7-11
7. The Solar System in October
8. Variable Stars South Symposium in 2016
9. Herbert Astronomy Weekend Report
10. Oxygen Doesn't Always Mean Life
11. ISS Photos Yield "Cities at Night" World Map
12. How to Join the RASNZ

1. Colin Keay 1930-2015

Colin Keay PhD DSc FRASNZ FAAAS FInstP FASA, who was born in Timaru died August 24th aged 85 in Brisbane. In the early 1960s Colin was lecturer in the Canterbury University Physics Department and used his initiative together with Frank Bateson to push for astronomy to become part of the Department's teaching and research (the formal department name change took place in 1991).

He initiated a programme of radar measurements of interplanetary meteoroid fluxes carried out at the Rolleston Field Station. Colin created a new branch of science called geophysical electrophonics: the production of audible noises of various kinds through direct conversion by transduction of very low frequency electromagnetic energy generated by a number of geophysical phenomena. Within 24 hours of the launching of the first satellite (the Russian Sputnik in 1957) he was the first to calculate that it would be visible over NZ. This led to the publication of the first two papers on observing a satellite.

He moved to the University of Newcastle Australia in 1965. He published the first papers on high resolution infra-red maps of Jupiter and was President of Commission 22 of the International Astronomical Union (IAU) and inaugural chairman of the IAU working group on the prevention of interplanetary pollution (space junk). In 1997 Minor Planet 5007 was named after him in recognition of his services to astronomy.

Colin was an accomplished science communicator and produced monthly newspaper articles on astronomy over several decades. He was founding president of the Newcastle Astronomical Society. He was active in the Australian community being the founding president of the Hunter Skeptics (1987) and President of the Newcastle Cycleways Movement (lobbying for more cycle tracks): in these, as in his science work, he was always enthusiastic in impressing his well-researched views.

-- Jack Baggaley

2. Auckland Ast Soc's Burbidge Dinner - Oct. 3

The Auckland Astronomical Society invites you to the 2015 Burbidge Dinner. The guest speaker this year is: Professor Chris Lintott from Oxford University, UK. His talk will be "Is the Milky Way Special?" See last month's Newsletter for details.

The evening will include the presentation of the Beaumont prize for the best article written in the Journal by a member and the Astrophotography Competition including the Harry Williams Trophy.

Date: Saturday, 3rd October 2015, starting at 6:30 pm. Venue: Alexandra Park, Epsom. Tickets: $60 per person. Includes a buffet dinner. Tickets can be purchased through the Astronz website or by emailing This email address is being protected from spambots. You need JavaScript enabled to view it. .

-- Jonathan Green.

3. Aoraki Mackenzie Starlight Festival - Oct. 9-11

Where: Twizel Events Centre, Twizel (with some events at Lake Tekapo and Mt Cook village) When: Friday 9 October 2015 to Sunday 11 October 2015. Why: The Festival will celebrate the creation of the southern hemisphere´s first International Dark Sky Reserve, in the Mackenzie Basin and at Aoraki/Mt Cook National Park in the centre of New Zealand´s South Island.

It will also mark the International Year of Light (IYL) 2015, which has been proclaimed by UNESCO to educate the public about light-based technologies and to recognize the role of light in the development of astronomy. Light has helped us to see and better understand the universe, which has enabled us to capture stunning images of the cosmos. IYL2015 will celebrate discoveries and breakthroughs in Astronomy and promote an appreciation of dark skies and the need to combat light pollution.

The Festival will comprise a mix of scientific, educational and cultural events over three days, designed to attract school students, family groups and members of the public who are interested in learning more about the stars, the night sky, the problems of light pollution and the appreciation of the environment and outer space. The events include stargazing, lectures, a concert, documentaries on the night sky, a photographic exhibition, and more. Prizes will be presented to the Winners of the earlier-organised Margaret Mahy Starlight Essay and Poetry Competition. Some events are free, while others have a nominal charge. See the website for ticket purchases.

The main Festival venue will be the Twizel Events Centre, 61 Mackenzie Drive, Twizel, South Canterbury. Some events will be at the Hillary Alpine Centre, Mt Cook village and at Mt John University Observatory, Lake Tekapo. Transport between venues will be organized by a festival bus for those who need it.

For details see the Starlight Festival at http://www.phys.canterbury.ac.nz/starlightfestival/

4. Astrophotography Weekend - Foxton Beach, Nov. 13-15

The Horowhenua Astronomical Society is hosting its third annual astrophotography weekend. This will be held at the usual venue: Foxton Beach Bible Camp, Foxton beach, Horowhenua on the weekend of 13th-15th November 2015.

The weekend is open to everyone interested in astrophotography from beginners to advanced. Come along and share your knowledge, tips and experiences. It is a great venue for undertaking practical photography so feel free to bring as much imaging equipment as you like. If you have anything to sell this is a perfect opportunity. There will also be practical workshops and talks throughout the day. Please book ASAP by going to the web address: www.horoastronomy.org.nz or email This email address is being protected from spambots. You need JavaScript enabled to view it.

-- Steve Chadwick

5. Stardate 2016 - Wairarapa, January 8-10

Stardate 2016 will be held at Stonehenge Aotearoa, near Carterton in the Wairarapa. This is the same venue where Stardate was held last year. The camp site will again be in the field behind the Visitors´ Centre. The main part of the programme will be based around the 8th, 9th and 10th of January but attendees will be able to arrive earlier by arrangement.

The facilities are still basic but we hope to add to these with time. Camping is the order of the day. Attendees will be able to use the toilets in the AV centre and basic showers will be erected. We do not have bunk rooms, however full details of local accommodation are available here: http://www.stonehenge-aotearoa.co.nz/Tours++Treks/Booking+Your+Visit/Carterton+Accommodation.html

Stonehenge Aotearoa will be in full operation during the period from 10 am to 4 pm. A free guided tour will be arranged for attendees during Stardate and some observing may take place from the henge after opening hours (depending on bookings).

Registration costs will be very similar to or the same as last year: $23 for adults; children (pre-teens) accompanied by parents free (these costs have yet to be confirmed by the Phoenix Council). We will arrange for a mobile caterer to visit the site, so that at least one meal during Stardate can be purchased on site.

This is an attractive site with good swimming holes in the Ruamahanga River just down the road. The wine growing areas of Martinborough, Gladstone and Masterton are within 30 minutes. There is a thriving tourist industry with many activities and venues available within the same distance.

If you are interested in attending Stardate 2016 please send an expression of interest to Kay Leather: This email address is being protected from spambots. You need JavaScript enabled to view it. with Stardate in the subject line.

We want to confirm programme details as quickly as possible and we want to put together a varied and interesting programme. If anyone has a presentation that they are prepared to make at Stardate 2016, please let Richard (This email address is being protected from spambots. You need JavaScript enabled to view it.) or Kay (This email address is being protected from spambots. You need JavaScript enabled to view it.) know as many details as you can. Hopefully, we can have a preliminary programme in the November newsletter.

-- Kay Leather.

6. Central Star Party, Hawkes Bay, January 7-11

Come and celebrate the first annual `Central Star Party´ - to be held in January 2016. The goal of the organisers, the Inter-Society Astronomical Advancement Committee (ISAAC), is to provide a fun social astronomical gathering laced with talks and activities. We plan to move the event around the central North Island over the years to various venues so that attendees from all locations can see/explore new parts of our great country, enjoy the local attractions, and catch up with any local friends and family. We think that doing this will make it a fantastic central North Island annual summer star party. We decided to hold the 2016 event at the Tuki Tuki Camp site in the Hawkes Bay since the owners have been doing the camp up recently and have demolished the old hall and built a new one. They also have two additional meeting rooms for alternate meetings, a new kitchen and three new dormitories that can house ten people in each. Accommodation is tenting, staying in the dormitories or using one of the four powered caravan sites. A number of people have expressed an interest to see and enjoy the new facilities at Tuki Tuki.

This premier 2016 event will run from Thurs 7th- Mon 11th (morning) January (four nights). Prices will be much cheaper than previous events held at Tuki Tuki - in 2016 an early bird attendee will pay $47 for the whole time (Thur-Fri-Sat-Sun nights) - as opposed to $101 in 2014.

If you want to give a talk or run a workshop then please let the organisers know - we´d love to hear what you can share...

Details can be seen at - http://www.censtar.party/

All the best and clear skies.

-- Inter-Society Astronomical Advancement Committee - (Gary Sparks (Hawkes Bay), John Drummond (Gisborne), Steve Lang (Auckland))

7. The Solar System in October

Dates and times shown are NZDT (UT + 13 Hours) unless otherwise stated. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in october

                            October  1  NZST              October 31  NZDT
                    morning  evening              morning  evening
       SUN: rise: 6.54am,  set: 7.28pm    rise: 6.07am,  set: 8.02pm
 Civil:    starts: 6.29am, ends: 7.54pm  starts: 5.40am, ends: 8.30pm
 Nautical: starts: 5.56am, ends: 8.26pm  starts: 5.04am, ends: 9.06pm 
 Astro:    starts: 5.23am, ends: 9.08pm  starts: 4.26am, ends: 9.45pm 
October PHASES OF THE MOON (times as shown by GUIDE)

Last quarter: October 5 at 10.06 am (Oct 4, 21:06 UT)

New moon: October 13 at 1.06 pm (00:06 UT)
First quarter: October 21 at 9.31 am (Oct 20, 20:31 UT)
Full moon: October 28 at 1.05 am (Oct 27, 12:05 UT)

LUNAR OCCULTATIONS OF PLANETS An occultation of Venus by the moon on the morning of October 9 will be visible from New Zealand. Despite being a day time event, the occultation should be readily visible in binoculars or a small telescope and probably with the unaided eye for those with good vision.

Later in the month, on the evening of October 26, the moon, only one day short of full, will occult Uranus, again visible from most of New Zealand.

More information on these events is given in the section for the planets.

THE PLANETS in October Only Saturn is visible in the evening sky, best viewed following sunset as the sky darkens. Mercury remains too close to the Sun to observe all month, while Venus, Mars and Jupiter have a get together in the dawn morning sky,

MERCURY is at inferior conjunction between the Earth and Sun on the morning of October 1 at about 4 am. At conjunction the planet will pass about 2.4° south of the Sun and as seen from the Earth. Mercury will be 0.656 AU, 98 million km from the Earth and 0.347 AU, 52 million km from the Sun.

After conjunction, Mercury becomes a morning object rising before the Sun. At its best, in mid October, the planet will rise 30 minutes before the Sun; by the end of October only 20 minutes earlier. In effect Mercury will not be visible at any time during the month.

VENUS, MARS and JUPITER in the morning sky during October. The three planets will start the month well spread out in the dawn sky.

VENUS will be readily visible as a brilliant point of light in the dawn sky throughout October. It rises 2 hours before the Sun on the 1st, reducing to about 105 minutes earlier by the 31st. It will be the furthest of the three from the Sun at the start of October.

MARS rises some 75 minutes before the Sun on the 1st, and 100 minutes earlier on the 31st, so then little different to Venus.

JUPITER rises 1 hour before the Sun on the 1st, almost 2 hours earlier on the 31st. So it starts October as the closest of the 3 planets to the Sun and ends the furthest.

As a result of these changing positions there will be some close passes during the month. On the morning of October 18 Mars and Jupiter will be 24' apart, a little less than the diameter of the full moon. Mars, magnitude 1.7 will be to the lower left of the far brighter Jupiter, magnitude -1.8. The planets will be low while the sky is still dark enough to see them. Half an hour before sunrise Mars will be just 9° up as seen from Wellington. At magnitude 1.7 Mars is likely to be difficult to see but Jupiter should be fairly easy to spot, at an azimuth nearly 20° to the north of east. Binoculars will then show Mars if it is not visible to the eye. The elongation of the planets, 40° from the Sun, means the worst of the glare should be to the right of the planets

Eight mornings later, on the 25th, Venus will be 1° above Jupiter. Half an hour before sunrise Jupiter will be some 12° up, so now a little better placed. The brightness of Venus will make locating the pair simple.

Finally the last morning of October will find Mars some 1.7° to the lower right of Venus. This is not their closest approach: that will be on November 3.

The crescent moon will pass Mars and Jupiter on the morning of October 10 when it will be at the apex of a triangle formed by it and the two planets defining its base. The moon, 9% lit, will be just under 3° from each of the planets. The three will be low with the moon a little over 7° up 40 minutes before sunrise.

OCCULTATION of VENUS, morning of October 9, NZDT In NZ the occultation takes place well after sunrise. Even so both phases of the occultation will be observable with binoculars or a small telescope. The light intensity of Venus will exceed that of the sunlit edge of the moon making the disappearance against the moon's lit limb observable. For New Zealand the occultations will take place fairly centrally round the moon's limb. The moon will be a 15% lit crescent

It will take about 90 seconds for the moon to cover the full diameter of Venus (30 arc second). But Venus will be only 40% lit, with the moon covering and exposing the unlit half first. Hence from the observer's point of view the occultation will start at about the time given in the table below for the mid event. The lit portion of Venus will be hidden or exposed to view over the following three-quarters of a minute.

The predicted times (NZDT am) for a number of places in NZ are given below, D = Disappearance and R = Reappearance:

Auckland:      D 8:11:59,  R 9:52:32
Hamilton:      D 8:14:35,  R 9:54:33
Palmerston N:  D 8:20:14,  R 9:57:26
Wellington:    D 8:20:34,  R 9:56:01
Nelson:        D 8:17:51,  R 9:52:16
Christchurch:  D 8:21:35,  R 9:52:01
Dunedin:       D 8:23:31,  R 9:48:01
Invercargill   D 8:21:44,  R 9:43:22

Times for other places will of course vary, even in different parts of the same city. Those who have the Occult program should generate their own predictions, otherwise Venus should be easily visible, weather permitting, a few minutes before the disappearance.

The occultation is also visible from the eastern half of Australia where the disappearance occurs in a dark sky and the reappearance around the time of sunrise.

SATURN will be the only naked eye planet in the evening sky. It sets just before midnight on the 1st and soon after 10pm on the 31st. So even it will be low especially by the end of the month when it will set an hour after the end of nautical twilight (Sun 13° below the horizon).

The planet starts the month in Libra but crosses into Scorpius on the 17th. Saturn will be about 10° below Antares, getting a little closer as the month progresses.

The 10% lit crescent moon will be about 5° below Saturn on the 16th. The following night it will be 9° to the upper right of Saturn.

OUTER PLANETS URANUS is in Pisces during October, being at opposition on October 12. It will then be 19.0 AU, 2840 million km from the Earth and 20 AU, 2992 million km from the Sun. Being at opposition mid October means it is in the dark sky all night throughout the month.

OCCULTATION OF URANUS. On the evening of October 26 an occultation of Uranus by the moon will be visible in NZ for places from just north of Auckland southwards. A grazing occultation occurs just south of Wellsford. The path of the graze is very close to the one for the graze of Uranus on the morning of September 2.

At the October graze the disappearance will be nominally at the unlit limb of the 98.3% sunlit moon, near its north pole. With the moon so near full, the disappearance of Uranus will be very close to the terminator of the sunlit region, especially in the northern half of the North Island.

Times of the disappearance vary from 11:09:17 at Auckland, the planet taking 36.2 seconds to completely disappear, to Hamilton 10:03:36 (21.4 seconds), Wellington 10:52:39 (12.8 seconds), Christchurch 10:46:54 (11.4 seconds), Dunedin 10:41:58 (10.4 seconds) and Invercargill 10:35:59 (10.4 seconds). The times are for the 50% occultation of the planet.

The reappearance takes place some time later ranging from 11:26:26 at Auckland where the planet will be behind the moon for just over 17 minutes to 11:30:54 at Invercargill with Uranus behind the moon for 55 minutes. This will be at the sunlit limb of the moon.

NEPTUNE was at opposition at the beginning of September, so it will be visible all evening throughout October. The planet will continue to be in Aquarius at magnitude 7.8 to 7.9, so is quite easily seen in binoculars. The 77% lit gibbous moon is closest to Neptune on October 23 when the planet will be 6° to the right and rather higher than the moon. The following night the two will be 10.5° apart with Neptune to the moon's upper left.

PLUTO continues to be in Sagittarius all October with a magnitude 14.4.

BRIGHTER ASTEROIDS: (1) Ceres is in Sagittarius during October its magnitude ranging from 8.7 to 9.1. Ceres will be moving to the east through Sagittarius towards the constellation's triple boundary point with Microscopium and Capricornus

(4) Vesta is in Cetus throughout October its magnitude ranging from 6.2 to 6.9 during the month. It is at opposition on October 3, when it is brightest. The asteroid will be moving to the west, 9 to 10° from beta Cet, Diphda (magnitude 2.0). On the 17th it will be on the line from beta Cet to iota Cet (3.5), with Vesta a little under 2° from the latter.

(15) Eunomia is in Pegasus during October its magnitude varying from 8.0 to 8.3 as the Earth moves away from the asteroid following its end of October opposition. The asteroid moves in an arc through Pegasus more or less centered on gamma Peg (2.8), 8.4° away.

(29) Amphitrite starts October at magnitude 9.3 in Aries. It is at opposition on the 23rd at magnitude 8.7 and crosses into Pisces 4 nights later. By the end of October its magnitude will be back to 8.9. During October, Amphitrite will be moving to the west about 3° from beta Ari (2.6). On the 23rd, gamma Ari (4.6) will be close to midway between beta and Amphitrite.

(471) Papagena will be at opposition in Cetus on October 21 with a magnitude 9.5. It will then be 1.5° from tau Cet (3.5) The two are closest on the 17th with Papagena 1.26° to the lower left of the star.

-- Brian Loader

8. Variable Stars South Symposium in 2016

The 4th Variable Stars South Symposium will be held in Sydney on Easter Friday, 25th March 2016. The venue is the University of Sydney´s Law Building (Camperdown Campus) which is centrally located, with good transport links, and plenty of accommodation options nearby.

The event is being held in conjunction with the 27th National Australian Convention of Amateur Astronomers, NACAA XXVII, which will run over the entire Easter Weekend. Chair of the Programme Committee is David O´Driscoll.

-- Alan Baldwin.

9. Herbert Astronomy Weekend Report

Eleven of us from Dunedin, Gore and Cromwell stayed the Friday night at Camp Iona, 2km to the west of Herbert township. The night was initially wet with cold showery rain, so we kept warm by the log-burner in the Lodge. At 9:00pm, the rain stopped and the dark night sky above us fully cleared. Telescopes and cameras were out in force, and we were treated to a broad auroral glow up to 30 degrees altitude in the southwest. It was the first aurora seen at a Herbert Astronomy Weekend since 1993!

Saturday was sunny and solar telescopes were in force. Four members of the South Canterbury Astronomy Group arrived. Robert McTague showed how to correctly align an equatorial telescope mount north-south by aiming centrally at the Sun at its exact transit time. Robert got Camp Iona's longitude and the Sun's transit time from his smartphone.

Later three more attendees arrived nearer Saturday evening, two from Dunedin, and another from Christchurch. A relatively new member of the Canterbury Astronomical Society set up his 12-inch Orion Dobsonian telescope, the largest aperture telescope of our Weekend. In the hall a data projector was set up for the talks. The intended evening speaker was late so, without an evening talk, we used another great clear night sky with telescopes and cameras finishing past midnight. I could detect a faint hint of the remaining broad aurora above the south- western hills.

Sunday morning saw a mass departure and a clean-up of Camp Iona. Despite only 18 attendees we had a very successful weekend of two clear night skies with an aurora.

Among those from Dunedin was Amadeo Enriquez of the Otago Museum and his "Astronomy Club" of four teenagers, two Year 12 students and two Year 9 students. They were keen astrophotographers with their DSLR cameras, especially on the aurora. One year 9 student, Stephen Xu, came from China last year. He had never seen so many stars in his life as he saw on the Friday night! And an aurora as well. A week after the event he is still buzzing from experiencing the night sky above Camp Iona!

-- From notes by Ross Dickie, Convenor.

10. Oxygen Doesn't Always Mean Life

The Earth´s atmosphere contains oxygen because plants continuously produce it through photosynthesis. This abundant supply of oxygen allows life forms like animals to flourish. Therefore, oxygen had been thought to be an essential biomarker for life on extrasolar planets. However, oxygen may be made by non-biological processes. Norio Narita of the Astrobiology Center of Japan's National Institutes of Natural Sciences (NINS) and Shigeyuki Masaoka, of the Institute of Molecular Science of NINS, have presented a novel hypothesis that it could be possible for planets to have large quantities of abiotic (non- biologically produced) oxygen. The study is published in Scientific Reports on September 10.

Until now, it had been thought that if a planet has oxygen that must mean that some form of vegetation are producing it through photosynthesis. Therefore, it had been assumed that when searching for signs of life on habitable extrasolar planets, the presence of oxygen in the atmosphere could be considered a definitive biomarker. However, non-biological chemical reactions can also affect atmospheric compositions of extrasolar planets. Now, the research team led by Dr Narita has shown that it is possible for titanium oxide to make abiotic oxygen by a photocatalytic reaction. Titanium oxide is abundant on the surfaces of terrestrial planets, meteoroids, and the Moon in the Solar System.

For a planet with an environment similar to the Sun-Earth system, continuous photocatalytic reaction of titanium oxide on about 0.05% of the planetary surface could produce the amount of oxygen found in the current Earth´s atmosphere. In addition, the team estimated the amount of possible oxygen production for habitable planets around other types of host stars with various masses and temperatures. They found that even in the least efficient production case of a low-temperature star, the photocatalytic reaction of the titanium oxide on about 3% of the planetary surface could maintain this level of atmospheric oxygen through abiotic processes. In other words, it is possible that a habitable extrasolar planet could maintain an atmosphere with Earth- like oxygen, even without organisms to perform photosynthesis.

Dr Narita said, "To search for life on extrasolar planets through astronomical observation, we need to combine the knowledge from various scientific fields and to promote astrobiology researches to establish the decisive signs of life. Although oxygen is still one of possible biomarkers, it becomes necessary to look for new biomarkers besides oxygen from the present result."

For the original text & image see http://www.nao.ac.jp/en/news/science/2015/20150910-abc.html

-- From a press release by the National Astronomical Observatory of Japan forwarded by Karen Pollard.

11. ISS Photos Yield "Cities at Night" World Map

Researchers on the ground have combed through a trove of images taken by orbiting astronauts to reveal unprecedented details about light pollution streaming from Earth's major cities.

Since the Mercury missions in 1960s, NASA astronauts have taken more than a million hand-held pictures of Earth. With the introduction of digital time-lapse imaging from the International Space Station (ISS), in the last decade the collection grew rapidly. Many of these NASA and ESA images are catalogued and publicly released in high-resolution on the Gateway to Astronaut Photography of Earth. Visitors can search photos of specific locations on the world map or search by coordinates.

The astronauts' images have scientific value in mapping the distribution and intensity of lights visible at night. Scientists from the Universidad Complutense de Madrid (Spain) and the Cégep de Sherbrooke (Canada), together with members of the public, have worked on a project called Cities at Night.

After three years of work, the team officially announced the program and its early results at the recent General Assembly of the International Astronomical Union in August. The aim is to produce a global colour map of the entire Earth at night. The first released version of the map presents selected densely populated areas.

Earlier maps of Earth's night lights were derived from Defence Meteorological Satellite Program (DMSP) images. These show resolutions of about 1 km per pixel, good enough to resolve towns and villages. NASA's Night Lights, known as the Black Marble and introduced in 2012, provides the improved resolution of 750 meters. These maps have been great tools for educators and science communicators, but they not convey colour or spectral information and do not resolve fine details necessary for advanced studies on light pollution.

But Earth-watchers were quick to realize the potential of images taken by astronauts aboard the ISS. While DMSP satellites orbit at altitudes near 830 km, the ISS orbits at roughly half that. Also, astronauts have access to an arsenal of lenses that range from an 8-mm Nikon fisheye to 1,200-mm super telephoto.

Like astrophotographers on Earth, challenged by constantly moving celestial objects, due to Earth's rotation, and long exposures, ISS photographers are also limited by the station's rapid velocity over the ground below (8 km per second). Night-time photography demands longer exposures, higher sensitivities, and faster lenses. In order to freeze the motion and capture a sharper image, astronaut Don Pettit fashioned a barn-door tracker from available parts on board, which enabled the first motion-compensated night time imagery from the ISS. The European Space Agency's NightPod, a motorized tripod installed in 2012, compensates for the station's speed and the motion of Earth below.

Thanks to these improvements, some images taken by astronaut aboard the Space Station can resolve details down to only a few meters per pixel resolution. According to Sanchez, on rare occasions and with advanced processing methods, the resolution can even reach only a meter per pixel - good enough to resolve individual streetlights.

However, the typical resolution range of astronaut images used in the project are 20 to 200 m per pixel, still far better than previous maps. The Cities at Night team has worked with more than 130,000 images since last year. Most of these were single photos made with lenses of 40-mm focal length and higher.

While astronauts' photography does not cover the entire Earth, the ISS's orbital inclination of 52° gives them an excellent stage for observing most populated areas of the world. Thanks to this resolution power the team were able to estimate the total cost of street light energy consumption in the European Union which is more than 6 billion euros per year.

NASA's Johnson Space Center provided images in their original (Raw) format, which enabled the team to analyse data in separate colour channels (RGB) and access valuable spectral information. Sanchez and his colleagues could also calibrate the cameras' spectral response, make flat fields for each lens, and stitch neighbouring images together to create mosaics, starting with some of the world's capitals.

For example, a comparison of images of Milan taken in 2012 and 2015 are very revealing. The newer image shows how the city centre is now dominated by brighter, bluer LED lights, having replaced older (but "warmer") high-pressure sodium street-lighting. This sudden change shows greater light pollution and a shift to wavelengths with greater impact on human health and the environment. (Blue light at night is harmful.) Such environmental monitoring is an important potential of the project.

According to Christopher Kyba (German Research Centre for Geoscience), who studies the ecological impact of artificial lights, "The ISS images are currently the only way to effectively study the global transition to solid state lighting (LEDs)." He notes that that these images have many uses beyond monitoring the spread of light pollution (and the consequent loss of starry skies). For example, they can play a role in many aspects of city planning: demographics, economics, ecological effects, conservation, and circadian disruption. They have even been used in studies that trace the causes and incidence of breast cancer and other diseases.

The ISS images record light directly straight up into the sky. However, according to studies by Chris Luginbuhl and others, the main cause of the skyglow we see at ground level is light beamed sideways, just above horizontal. On their long glancing path through the atmosphere, photons scatter much more strongly than those directed toward the zenith.

An important part of the new study led by Sanchez is to correlate what's seen in the astronauts' images with the light pollution seen from the ground. The photos do contain evidence of diffuse skyglow, but up to now this had not been measured quantitatively. Prior surveys such as the World Atlas of Artificial Night Sky Brightness indirectly estimated skyglow brightness based on satellite images. However, amateur astronomers now routinely measure skyglow using portable devices such as the Sky Quality Meter or by even smartphone apps. The Cities at Night team implemented some of these ground-based measurements in the project. This space-ground correlation, done for the first time, is an important step in creating more reliable estimates of actual light pollution.

"This project is incredibly important for science and really doesn't cost a lot of money," Kyba says. "It would be a real shame if it's not successful." If you're interested in supporting it, the project recently started a citizen-science effort and crowdfunding on Kickstarter to continue and extend the map.

See more at: http://www.skyandtelescope.com/astronomy-news/iss-photos-yield-cities-at-night-map-09052015/?et_mid=782828&rid=246399573#sthash.tRkGDrpw.dpuf

For more information about light pollution and how to fight it, check out the extensive website of the International Dark-Sky Association. Better yet, become an IDA member!

-- From the above Sky & Telescope article by Babak Tafreshi.

12. How to Join the RASNZ

RASNZ membership is open to all individuals with an interest in astronomy in New Zealand. Information about the society and its objects can be found at http://rasnz.org.nz/rasnz/membership-benefits A membership form can be either obtained from This email address is being protected from spambots. You need JavaScript enabled to view it. or by completing the online application form found at http://rasnz.org.nz/rasnz/membership-application Basic membership for the 2015 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
P.O. Box 57 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lake Tekapo 7945
New Zealand