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The Little Gem Nebula (NGC 6818)

This one is well-named. The Little Gem Nebula subtends a tiny visual angle; just 22 by 15 arcseconds. For those visitors unfamiliar with astronomical measurements, look at the back of your hand while it is at arm's length covering part of the sky. Point your little finger upward. It's width is about one degree. Take that width and divide it by 3600. That is one arcsecond - as I said, tiny. It's no wonder we need good telescopes and clear, still skies to view some of these objects.  The Gem Nebula is a planetary nebula (PN) that sits about 6.4 kly away in Sagittarius. Like all PNs, it is the remnant of a star that began its life weighing somewhere under 8 times our Sun's mass. In its final stages of life, such a star expands to become a red giant, then the core collapses into a white dwarf. This core bombards the gas shell with such a high level of radiation that it lights up. With very thin shells, we are better able to see the edges than the middle, which is why so many PNs appear as ring-like structures to us. The Gem is obviously an exception -  quite bright across its entire width, giving it an apparent magnitude of 9.39. The mottled appearance arises from the fact that NGC 6818's gas envelope actually has two layers. The inner one is shaped a bit like a vase, while the outer one is more like a regular bubble. The overall teal-blue colour likely comes from ionised oxygen (Pottasch et al., 2005). PNs have quite short lives by astronomical standards; usually less than 10,000 years. In an analysis of its spectra, Hyung et al. (1999) have suggested that NGC 6818 is about 9,000 years old so it is well along its lifespan. I know the feeling, Little Gem. Date: 11 August, 2018
R.A.: 19h 44m 02s
Dec.: -14° 09' 29"
Photo stuff: 14 subs @ 180s ea.; ISO 800; Canon 60Da on RCX 16" f/8
 

Gary

Gary

Nebulae in the SMC

These are a collection of gas nebulae in the Small Magellanic Cloud. Chadwick and Cooper, in their excellent book "Imaging the Southern Sky", have named the collection The Magnificent Seven (tilt your head to the right to see why). The photograph is an example of narrow-band imaging. The term narrow-band refers to the fact that the filters used during the data collection process allow light only from very specific regions of the visual spectrum in which electrons are jumping between energy levels. In this case, the image is a composite of the light from hydrogen (H-alpha @ 656.28 nm, reddish; H-beta @ 486.00 nm, blue) and oxygen (O-III @ 500.70 nm, greenish). Research astronomers will use these bands - and many others - to discover much about the nature of an object. Astrophotographers tend to use them like a palette of paint, although we often are quite interested in the same things as the pros but at an amateur level. The other benefit of narrow-band imaging for astrophotography is that it can be done in full moonlight. Because the moon does not emit light in these ranges, moonlight is, essentially, ignored by the camera sensor. The trade-off is that one needs an enormous (!) amount of exposure time to get even half-decent results. Date: 26 July 2018
R.A.: 00h 47m 47s
Dec.: -73° 14' 04"
Photo stuff: 12 subs @ 300s ea. for each band; ISO 1600; Canon 60Da on Meade RCX400 16" f/8; 0.7 focal reducer.                            

Gary

Gary

Lunar eclipses and selenelions

Saturday morning saw us take on the challenge of carrying the 12 inch telescope up the Port Hills to Victoria Park in an attempt to help people understand the lunar eclipse phenomena and what they were seeing. We chose a location that we thought was readily accessible, but forgot to take into account the gates would be shut at that time of day (we'll learn for next time). So we set up on the side access road to the dog exercise area and were very shortly joined by around 100 people and a camera crew from Newshub.   There had been a lot of discussion in the media about the theoretical astronomical event of the selenelion, where both the eclipsed moon and the sun could be visible in either horizon. Whilst the theory might be correct, in practicality, there is no way this event would ever come to light, if you excuse the pun. A darkened, eclipsed moon against a brightening sky would mean the moon would become invisible at least 20 minutes prior to sunrise. However, despite clear skies overhead, ultimately the event was cut short (even before totality occurred) by a Nw'erly cloud bank being held back by the mountain range.           Despite that, everyone seemed to enjoy themselves and took in the spirit of a beautiful morning and sunrise. The resulting article was well produced and included footage of people viewing the event through the telescope and concluded with a short interview from one of our Directors, Gary Steel.               Click below to see the report from Newshub Blood moon Kiwis turn out in droves to look for the selenelion.mp4

NGC 7009 - Saturn Nebula

This wee object is a bit of a challenge to capture & process, but worth the effort. Planetary nebulae typically subtend a very small visual angle; this one is no exception at approximately 30 x 24 arcseconds. The Saturn Nebula sports some very clear ansae (the two bright knots in the 'rings') and a very pretty blue-green halo that suggests ionised oxygen. Aller's (1961) spectrograph seems to confirm this (Kaler, 1997). It is no great surprise, given the quality of optics at that time, that Lorde Rosse (~1848) thought that it might be a planet similar to Saturn, and thus gave it its current name. We now know that that its core is a very hot, collapsed star, surrounded by an envelope of gas that was pushed out by stellar wind after the collapse. The distance to NGC 7009 is, apparently, difficult to determine; some estimates state it being as close as 1400 ly, while others suggest it is up to 4000 ly away. Date: 24 August 2017
Constellation: Aquarius
R.A.: 21h 04m 12s
Dec.: -11° 22' 13"
Photo stuff: 93 subs @ 180s ea.; ISO 800; Canon 60Da on Meade RCX400 16" f/8                                

Gary

Gary

IC 4685

This image covers a massive star formation region approximately 4 kly away, and contains several nebulae. The largest is the emission nebula IC 4685, in the central portion of this photograph. The dark, dust lane of Barnard 303 snakes across it and points to the bright, white star (V3903 Sgr; an Orion-type variable) in the middle right. The blue reflection nebula on the lower right is NGC 6559. In the lower left corner is fainter IC 1275. It is possible that the emission nebulae are part of a river of hydrogen connecting to M8, the Lagoon Nebula, which is a nearby neighbour. Date: 11 July 2016
Constellation: Sagittarius
R.A.: 18h 09m 28s
Dec.: -23° 59' 04"
Photo stuff: 57 subs@s 180s ea.; ISO 800; Canon 60Da on Meade RCX400 f/8 with 0.7 focal reducer                                        

Gary

Gary

The Large Magellenic Cloud (LMC)

This is a wide field image of the Large Magellanic Cloud. NGC 2070 (The Tarantula Nebula) is clearly visible at centre right, an N11 (The Bean Nebula) is in the lower left corner. In fact, the LMC is chocka with what astronomers refer to as DSOs, or deep space objects. Almost any condensed knot of light has a designation in one or more astronomical catalogues. The central bar of the dwarf galaxy is clearly visible in this image. It is thought that some of the LMC's spiral arms were ripped off in tidal interactions with the Small Magellanic Cloud and our own, much larger, Milky Way galaxy, which just goes to show that it's a galaxy-eat-galaxy universe out there. The LMC can be seen straddling the border of the Mensa and Dorado constellations, and is approximately 163 kly away. Date: 21 October 2016
Constellation: Dorado/Mensa
R.A.: 05h 23m 35s
Dec.: -69° 45' 22"
Photo stuff: 50 subs@120s ea.; ISO 800; Canon 60Da with Canon 28-135mm; f/5.6    

Gary

Gary

IC 1274

There is rather a lot going on in this image. IC 1274 is the circular structure in the top, middle-right section of this photo. It is an HII region, sitting on the near edge of  a seriously large molecular cloud known as Lynds 227. A dark nebula (Barnard 91) defines the top edge of the nebula. The bright star in the center of IC 1274 is a young, energetic B0 V star (HD 166033); current thinking is that this is the star that has blown this massive bubble (Dahm et al., 2011). The nebula, itself, contain many stars in the B0-B5 range, which suggests that this is a population of new stars. The entire image is part of a highly productive stellar nursery that contains several fascinating deep-sky objects. Date: 12 July 2018
Constellation: Sagittarius
R.A.: 18h 09m 29.9s
Dec.: -23° 42' 36.3"
Photo stuff: 58 subs@180s ea.; ISO 800; Canon 60Da on Meade RCX400 16" f/8; 0.7 focal reducer  

Gary

Gary

The South Pillars

The Carina Nebula, where the South Pillars region exists, has an incredible array of fascinating objects and processes. In this image, for instance, we see pillars - also known colloquially as "elephant trunks" - of dust in which stars are being born. The best example in this photo is in the lower left quadrant. Recent research (McLeod et al., 2016) has suggested that such pillars are likely to disappear once the star comes into being due to a process known as photoevaporation, in which the powerful stellar wind from the new star literally blows away its cocoon. Date: 20 March 2018
Constellation: Carina
R.A.: 10h 45m 29.1s
Dec.: -60° 03' 21.9"
Photo stuff: 20 subs@180s ea.; ISO 800; Canon 60Da on Meade RCX400 f/8; .7 focal reducer

Gary

Gary

Fornax Cluster

These four are a suite of galaxies that are part of the Fornax cluster. Clockwise from top left: NGC 1375 (34 Mly), 1380 (86 Mly), 1373 (61 Mly), & 1374 (59 Mly). There are plenty of other galaxies visible in the background. Look for the elongated smudges of light. Date: 10 October 2016
Constellation: Fornax
RA: 03h 35' 57"
Dec:  -35° 05′ 04.1″
Photo stuff: 32 subs@300s ea.; ISO 800; Canon 60Da on Meade RCX400 16" f/8; .70 focal reducer  

Gary

Gary

The 9 stars of Matariki

Matariki is the Māori name for a cluster of stars. This year, from July 6 to 9, Matariki will re-appear in the dawn sky – signalling the start of the Māori New Year.
 
It is a time to celebrate new life, to remember those who’ve passed and to plan for the future. And it’s a time to spend with whānau and friends – to enjoy kai (food), waiata (song), tākaro (games) and haka.
 
Our tūpuna (ancestors) would look to Matariki for help with their harvesting. When Matariki disappeared in April/May, it was time to preserve crops for the winter season. When it re-appeared in June/July, tūpuna would read the stars to predict the upcoming season – clear and bright stars promised a warm and abundant winter while hazy stars warned of a bleak winter.
 
Because Māori follow the Māori lunar calendar, not the Gregorian calendar, the dates for Matariki change every year. It is a common belief that Matariki has seven visible stars. But Matariki actually has nine visible stars, according to leading Māori astronomer, Dr Rangi Matamua, who has been researching Matariki for over 30 years. As part of his research, Dr Matamua found that some of his own tūpuna were able to see nine stars.
 
The nine visible stars include: Matariki, Tupuārangi, Waipuna-ā-Rangi, Waitī, Tupuānuku, Ururangi, Waitā, Pōhutukawa and Hiwa-i-te-Rangi.
 
Each star holds a certain significance over our wellbeing and environment, as seen from the Māori view of the world.   Matariki1_LowEnglish.pdf

Winter solstice

At 22:07 tonight the sun reaches the northernmost point in it’s annual journey around the sky. We go past our shortest day and from tomorrow the days get longer. So, if you are in the Southern hemisphere, happy winter solstice. It’s also the longest night of the year, so go out and enjoy our amazing Southern Hemisphere sky! 

The rise of Matariki

The rise of Matariki signified the start of the New Year for Maori. This year Matariki begins today and if you’re a keen stargazer hoping for a glimpse of the star cluster tonight, then you need to be aware of the simple fact that catches out 99% of people interested in viewing the constellation: It rises early in the morning. At when first viewed is quickly extinguished by sunrise. As the year goes on though, it does get higher in the sky, but New Year is about the RISING, so you need to get up early and look east from around 6:30am In English, the cluster is known as the Pleiades, its ancient Greek name, or the Seven Sisters. The Hawaiian name is Makali'i, or 'eyes of royalty', and in Japan it is Subaru, meaning 'gathered together'.   The reappearance of the seven Matariki stars - which translated have two meanings: mata ariki (eyes of God) and mata riki (little eyes) - signals the beginning of the Māori New Year.   

A sky full of planets

The night sky is continuing to fill up with planets with all of them visible at some point during the night. Now all we need are some clear skies. Keep watching our weather pages for a guide as to the probability of getting some views. Maybe not the most impressive shot of Jupiter you ever saw. What if I tell you that it was taken with a standard phone camera through our main telescope?

Jupiter is nice and up in the sky with the four moons visible most of the time.

Alpha Crucis

I love the halo effect on Acrux when photographed. The bright star Alpha Crucis marks the base of the Southern Cross, and at magnitude 0.8, ranks as one of the brightest stars in the southern skies. Also known as Acrux, this star is an excellent multiple star system for binoculars and a small telescope. And it’s one of the few double stars that can be resolved with a telescope during daylight hours. Acrux could not be easier to find. At magnitude 0.8, it’s the brightest star in the constellation Crux and the 12th brightest star in the night sky but 321 light years from Earth
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