At the limit

October 30, 2015 by grahamrob in Deep Sky Objects, Equipment, Imaging and tagged Galaxies, Pegasus, Photography | Leave a comment

Earlier this month the weather and clear skies produced particularly good imaging conditions that resulted in some excellent pictures; it’s already a distant memory as the weather has since turned cold and cloudy day-after-day – or at least every night except when there’s a full Moon! With these images knowingly in the bag and the telescope well aligned, I took the opportunity to indulge in a short session imaging some galaxies that happened to be around the Meridian at this time which, as it turned out, were located in proximity to the constellation of Pegasus.

Two of the objects (M74 & NGC 7814) were confined to just ten shots and the third fifteen, all at 180 seconds exposure and ISO 1,600. For such dim and distant objects this in itself was obviously insufficient but still it was fun to experiment. As expected the resulting images are feint and noisy but the object’s form can be clearly seen and, in the case NGC 7814 – the Little Sombrero, even the edge-on dust lanes are evident.

In order to better understand the limits of the equipment, a comparison of the images with the objects’ physical information given side-by-side illustrates the problems and possibilities for the future. The truth is that these are all at or beyond the realistic limit of my current set-up but I was interested to see what results could be achieved and I always enjoy their beauty, even if imperfectly captured.

Apart from the obvious problem of size, mainly a function of distance in this case, their apparent magnitude is also challenging. It is interesting to consider that using the 18 megapixel Canon 550D and WO GT81, each camera pixel which measures 4.30μm samples just 1.855 arc seconds per pixel and therefore even the largest of these objects (M74) spans an area of just about one tenth of a degree (0.10^o). Better alignment and longer exposure should tease out more detail but as the recorded image of each object is no more than 2% of the total image the reality is that I am pushing my luck.

Still it is fun and I have managed to capture a few of the photons that left these galaxies so long ago. As my equipment, techniques and knowledge continue to improve then hopefully so will the limits. Watch this space!

Rock On!

October 19, 2015 by grahamrob in Deep Sky Objects, Equipment, Imaging, Widefield Imaging and tagged Andromeda, Cygnus, DSO Imaging, Nebulae, Photography, Star Clusters | 2 Comments

Due to my viewing limitations at Fairvale Observatory planning is essential, with the best imaging range mainly restricted to a zone between 65^o and 85^o and within +/-20^o of the Meridian. Furthermore, as I am mostly using the William Optics GT81 telescope at the moment, imaging targets should preferably be large – something between 1^o& 2^o is perfect, such as the Rosetta Nebula at 1.3^o or Andromeda Galaxy at 190’ x 60’. As luck would have it these conditions are favourable for a number of objects at the moment and I have been somewhat spoilt for choice: North America Nebula, Veil Nebula and Andromeda.

Notwithstanding, for some reason I have until now overlooked the Sadr Region IC 1318, which is also large and in a similar part of the sky as the aforementioned North America and Veil Nebulae but perhaps overshadowed by their notoriety. In reality it is an enormous area of nebulosity containing many features worthy of imaging which are perfect at this time of the year from my location.

Sadr Region: green rectangle indicates the approximate area of IC 1318 image, yellow rectangle the NGC 6888 Crescent Nebula image.

IC 1318 is a diffuse emission nebula surrounding the star Sadr or Gamma Cygni, which is at the centre of the Cygnus Cross and on the plane of the Milky Way. The Sadr region is located deep within the Orion arm of the Milky Way about 3,000 light-years from Earth, with Gamma Cygni actually situated closer in the foreground. Such is the size of IC 1318 that its three constituent parts, A – B – C, extend over some 200 light-years or about 4 degrees, which is well beyond the FOV of the WO GT81; how could I have overlooked his enormous area of nebulosity before? As a result of its size and complexity I also chose to image two other interesting features nearby.

IC 1318 Sadr Region – image inverted & annotated

IC 1318 Sadr Region
WO GT81 + modded Canon 550D & FF | 30 x 120 secs @ ISO 1,600 | 30th September 2015

Situated just above Sadr is the small star cluster of NGC 6910 AKA Rocking Horse Cluster. Although only 10’ in size the cluster is visually quite prominent, though I struggle to see the little horse that others have identified. Notwithstanding, it is an interesting and attractive part of the Sadr region.

NGC 6910 The Rocking Horse Nebula as recorded by StarObersever.eu – located just above Gamma Cygni in the previous image.

Located about 2 degrees south west of Sadr is the Crescent Nebula NGC 6888, which is not unlike the Jellyfish Nebula in appearance but is younger in its evolution. An emission nebula, NGC 6888 is formed by a stellar wind from the Wolf-Rayet star WR 126 colliding with a slower moving wind ejected when the star previously became a red giant. The result is an illuminated shell-like feature consisting of two shock waves, one moving inward and the other outward, producing this amazing spectacle which measures some 25 light-years across. Near the end of its existence, the star will eventually end its life in a spectacular supernova explosion – now that would be an image.

NGC 6888 Crescent Nebula
WO GT81 + modded Canon 550D & FF | 20 x 180 secs @ ISO 1,600 | 9th October 2015

Crescent Nebula – cropped

Crescent Nebula – GradientXTerminator applied

Whilst IC 1318 has proved to be an excellent and productive imaging target for my equipment, it has become clear that it represents a much, much larger area of nebulosity that incorporates or is at least immediately adjacent to NGC 7000, the North America Nebula. At a rough estimate this larger area spans a distance of some 2,000 light-years and is some 50-times bigger than the Sadr region. Like other major areas of nebulosity (Barnard’s Loop) such a scale is way beyond the ability of my equipment and most others without resorting to a mosaic technique.

However, my interest in seeing and potentially imaging the bigger picture has been piqued and I have recently purchased a Vixen Polarie tracking mount, which can be fixed onto a camera tripod with a standard camera and lens in order to take long exposures without forming star trails. This set-up has two advantages over prime focus + telescope imaging: (i) it is highly portable and can easily be taken anywhere in a rucksack, and (ii) by using a camera lens of say <=50mm focal length it is possible to achieve a much wider FOV and thus photograph some of these very large nebulous areas in one image.

Alas the Sadr region is now moving on and it is probably too late to tackle using the Polarie mount but it will be something to look forwards to again next autumn and meanwhile Orion is just round the corner. Watch this space for developments!

Space Odyssey

October 9, 2015 by grahamrob in Deep Sky Objects, General Astronomy and tagged Andromeda, DSO Imaging, Galaxies, Messier Objects | 3 Comments

I have just finished reading Chris Hadfield’s excellent book An Astronaut’s Guide to Life on Earth, which is an entertaining and insightful look at being an astronaut and the lessons it provides for life in general. Who of us has not at least considered such an adventure ourselves but, of course, it is impossible for all but a few.

Astronomy is thought provoking enough in itself looking out at the vastness and beauty of the Universe, being in space and looking down on our planet would take such thoughts to a whole different level; from their subsequent accounts it is clear that those who have walked on the Moon became changed people, returning different to the rest of us.

Ever since following the pioneering space adventures of Yuri Gagarin and Alan Sheppard and especially watching the Apollo 11 Moon landing in 1969, I have been fascinated by space, its science and the human experience of travelling there. My solution to going into space was to take up scuba diving and since 1976 have had many wonderful diving experiences all over the world. Of course, it’s not space but it is very much other worldly and the weightless feeling is as close as most of us will get to being in space; the astronauts train extensively underwater for just that reason. Furthermore, as a geologist and more recently taking up astronomy has altogether provided me with a better understanding of the Universe.

Maldives, Kandooma 2004: the closest I’ll get to space!

Given my long standing interest in space, it is perhaps surprising that I came late to astronomy itself, so why now? The best answer is time – in recent years I have had more of it and in the past work, family and extensive travel precluded such a pastime. Like so many sciences in the modern era, technology has also unlocked major new opportunities for scientists and amateurs alike. Whilst I enjoy the science itself and especially viewing the night sky, the ability to produce frankly incredible images has been the most important key to my recent personal interest.

The phenomenal imaging improvements that have occurred since the launch of Hubble have made the power and beauty of the Universe even more accessible to us all on Earth. Digital image capture and processing is now so powerful that pictures of hitherto unimaginable quality can be achieved from Earth. Furthermore, for a relatively modest cost outlay, such images can be obtained by amateurs like me, literally outside my back door. More than any other development, this is what has now engaged my interest. The product of astroimaging can easily be overlooked as just an attractive, often spectacular photograph of the night sky – and they are. But the equipment and pictures produced are also important tools that can assist our understanding as well as imagination of space.

After a forced absence from astroimaging for the past six months, I was recently fortunate to obtain a number of exciting pictures of familiar objects on my first night back, in particular M31 or the Andromeda Galaxy. As the nearest galaxy to Earth, Andromeda is an obvious target for those new to astroimaging but despite its proximity, it is not to be underestimated as an imaging target. I have attempted imaging M31 before but, like many others, found it very difficult to coax out the detail which makes it such a beauty. I am not completely sure what was different this time but the resulting picture at last starts to capture these details; I was even more surprised at the outcome which is the result of just nine 120 second exposures at the end of a long night before heading for bed!

M31 Andromeda Galaxy
WO GT 81 + modded Canon 550D + FF | 9 x 120 secs @ ISO 1,600 | 19th September 2015

Andromeda poses two main challenges for the photographer: (i) the contrast in brightness between the central area and the rest of the galaxy, and (ii) the need to show the brown dust bands within the main disc, which provide a fascinating insight into the galaxy’s overall structure – that is not unlike out own Milky Way. The classic technique is to use two sets of images, with camera settings appropriate to the two contrasting areas, subsequently bringing them together during post-processing. Despite the limited number of prime focus images taken the final picture achieved still came out well. Though the bright central area is overexposed, the galaxy’s dust bands are clearly evident and for the first time have captured the full character of this magnificent feature. Furthermore, within M31 the NGC 206 is evident, a star formation region of over 300 new stars, whilst in the adjacent sky two other Messier galaxies are shown in the image M32 and M110.

M31 Anfromeda Galaxy: inverted & anotated

M31 Andromeda Galaxy: inverted & annotated

I think it is correct to say that the Andromeda Galaxy is one of the iconic images of the night sky and I feel obtaining such a picture marks another notable point in my personal space odyssey. I would hope Chris would approve, as well as Major Tom?