AnnMarie's Blog

Whilst experimenting with the SX Lodestar the other night, I decided to take a few frames of the moon which was looking particularly lovely. Using a 752×580 sized chip at 1500mm focal length I’d have a section of the moon with each frame. So I took 12 frames in a less than ideal arrangement (but there we go) and covered all of the visible phase of the moon.

  Click here to see a larger view …

As you can see, I later combined the individual images into 1 mosaic of the moon that evening. It’s not perfect but I’ve learnt some things about creating an Astrophoto mosaic, something that I would like to do more of. The full size image contains quite a lot of data, this is definitely an interesting technique.

Messier 51, The Whirlpool Galaxy, rates as one of my favourite galaxies to image. The gravitational interactions between the two galaxies have created a beautiful spectacle.  Below is my most recent image, but first some of the image background:

I am in the process of providing our mount with guiding capabilities, the camera for which, will be a Starlight Xpress Lodestar. This is based on an excellent quality Exview CCD (the ICX429AL) and all built into a 1.25″ eyepiece type barrel. Anyhow I have the camera but no lens or adapter yet, so whilst guiding isn’t an option, I thought I’d try a little imaging with the guide cam. I collected 1hour 10minutes of luminosity with the Lodestar and added to that 35minutes of colour data from my Canon 20D. Here is the resulting image:

   Click image for a larger view …

I’m quite pleased with the results from this unusual combination of cameras. All data was gathered through the C6SGT operating at f10 and at 3-4 am in the morning. I was barely functioning but the -3 degrees C was helping the uncooled cameras, no darks or flats were used for the Lodestar but they were used for the 20D. As normal Iris, Photoshop & Lightroom were used for the processing.

M51 data:

• Visual Brightness: 8.4
• Distance: 37 million light years
• App. Size: 11 x 7 arc mins
• Constellation: Canes Venatici

The Pacman in Cassiopeia is another of those deep red nebulas that are currently challenging my imaging. Again it is an area of nebulosity illuminated by hot young stars. The gases emit a variety of light wavelengths but H-alpha emissions are very much in prevalence. Here’s an image ..

The nebula is designated NGC281 and is named for its rather reminiscent likeness to the hero of the 1980′s video game. The nebula required over 3.5 hours of exposure and some tricky processing to produce the image above.

{see my newer post for an improved picture} 

The Rosette Nebula is located in Monoceros ( the Unicorn) and comprises of NGC2237 – 9 & 46. It is a large mass of dust and ionised gas. At its core is NGC 2244, a relatively young cluster of stars, freshly formed from the nebulous dust. These hot young stars help to illuminate the nebula, as pictured below:

  Click image for larger view …

The nebula is about 5500 light years away and it appears in our winter skies as a beautiful astrophotography target.

Given the large proportion of infra-red light emitted by this nebula, it is yet another target that begs a modified or specialist camera. However my trusty Canon 20D has again performed admirably; here are the imaging details:

• Canon 20D 100-400L @ 250mm
• f5.6
• ISO 1600
• 1hr 52.5mins in 75 subs
• Iris, PixInsight, Photoshop & Lightroom for processing.

Technorati tags: AstroPhotography, Monoceros, Rosette

The Hyades is a beautiful open cluster of about 150 – 200 stars located in the constellation of Taurus. The cluster is named after the daughters of Atlas & Aethra,who were therefore half sisters to the Pleiades. Aldebaran or Alpha Tauri is the brightest star in Taurus, it is a mere 68 light years from Earth and about 40 times larger than our Sun. It is a red giant with almost 100 times the luminosity of the Sun.

  Click image for larger view …

Taurus is the constellation of the Bull and it contains 2 beautiful star clusters the Pleiades & the Hyades.

The Hyades: Greek mythology does not agree on how many sisters there were, 5 6 or 7 but seven stars are named after them as shown in the picture above. Aldebaran is also labelled but it is not a member of the cluster. The Hyades open cluster lies about 150 light years away from Earth and has been known to mankind since prehistoric times. The cluster is one of the closest to earth. It’s distance having been calculated from basic geometry, it is one of the corner stones of setting up our astronomical distance scale. The classic ‘V’ shape of this cluster runs from the Bull’s eyes down towards its nostrils.

About the image: Taken during one of the few clear nights of the last few weeks. I was experimenting with mixing different apertures for a wide field object; I don’t think any advantage was gained by so doing. The image is a small stack of images, amounting to 10 minutes total exposure mainly at f6.3. Processing was in Iris, Photoshop & Lightroom, as usual.

Find out more about the Hyades at their SEDS page.

A little time ago I wrote an article for a Home Education magazine. It was a light look at how I started taking pictures of the sky and how others could easily join in. I thought this might be worth posting to my blog – so here it is …

    A sight to stare at. Early morning at home, after a night’s astrophotography.

“Always got her head in the clouds”

I was six years old and sitting in the classroom of my local village school. It had a large window which looked out across meadows & farmland. Today was summertime and I was watching the buttercups nod in a light breeze, bathed in a beautiful golden sunshine. My mind wandered, how amazing it all is from the beautiful flowers to the Sun and heaven knows what other fascinating things in the sky above.

“Jones!” yelled the teacher,”You’re not listening!”

“I am Miss” I replied, followed by a verbatim quote of the last 30 seconds of her lecturing.

Then I was punished, for showing off. I never really did get the attitude of schools & some teachers. What I did have was a fascination, a curiosity for all things ‘nature’, including the sky. Here started my voyage into Astronomy & Cosmology.

If you’re out under a clear dark sky one night soon, move away from any artificial light, turn off your torch and stare upwards. Your eyes will gradually become accustomed to the dark and more stars will come into view. Look for the milky patch across the sky, that’s the Milky Way, our own galaxy. It contains about 200 billion stars. The Universe beyond? Well there’s more stars there than all the grains of sand on all the beaches of our planet. And stars don’t account for half the matter out there.

Pictures & a thousand words

Another interest of mine is the use of cameras. I guess it really developed when I was a teenager but I have only fully indulged it within the last decade or so. Photographs can record a moment in time, a memory, that’s what most of us use them for. But that’s not all they can do. Some use them to provoke strong emotions, more than any passage of pros might do; take anti-war journalism for example. For others, the camera can show us sights that our eyes can’t – this is where one of my interests lies. Freeze the motion of a running animal with a fast shutter speed, take a macro shot of an insect feeding on a flower, point the camera down a microscope to reveal the tiny world around us; all these techniques & more, expand our awareness, our comprehension of the things around us. I suppose it was only a matter of time before I wished to put camera & telescope together.

If you have a camera that can take long exposures (more than say 30 seconds), take it out on a dark starry night, put it on something secure preferably a tripod, set the zoom to wide angle & point the camera upwards about 50 to 55 degrees (in the UK) & northwards. Experiment with the exposure time but start with 15 minutes or so.

The resulting image will show stars apparently rotating around a point (the celestial pole) in the sky. You’ve just taken your first astrophotography picture and have also demonstrated the spin of our planet on her axis!

With just a camera & tripod you can also take good pictures of the moon, aurora (if you’re lucky) and even record a few planets (Venus, Jupiter, Saturn, and Mars) but they won’t look very big, for that you’ll need a telescope.

Stardust Fairies

Tamsin (our daughter) has, like most children, a wonderful imagination and it helps her jump from one thought to another. This was the case here. She had been thoroughly enjoying reading a series of books about “Stardust Fairies”. Within the tales, each fairy has their own special star; Regulus being one of them. Tamsin wanted to see Regulus (Alpha Leonis) so we checked on its positioning, first star of the constellation Leo, and pointed it out to her. Did you know that Regulus used to be called Cor Leonis, the lion’s heart, so it’s a star for all you courageous home-ed families out there.

We then became involved in a project to survey the darkness of Britain’s skies. To complete the survey you needed to count the number of stars that you can see in Orion’s belt. Tamsin loved it and from here it was but a small step to her wanting a telescope to further her interests in Astronomy.

We bought a 6 inch Schmidt Cassegrain (SCT) scope & an equatorial mount to put it on. There are several different types of scope; the SCT is probably the jack of all trades. It is good for planet viewing & deep sky objects and suited to visual or photographic use. The equatorial mount allows the scope to slowly track across the sky counteracting the rotation of our planet (as you photographed above).

The Low Down

So what do you need to get started? Well the great thing about astrophotography is that it’s easy, simple & cheap; it’s also difficult, complex and expensive. Did you get that? What I mean is that this is an interest that you can start off easily and grow it to become as involved as you wish.

Obviously some sort of camera is a necessity, your current one is probably sufficient for getting started. Modern digital cameras are great, they give you immediate feedback, are fairly sensitive and many have access to multiple settings. Read on for details of different techniques and what’s involved.

The Moon	Setting Sun (with sunspots)

Please note: never look at the sun or image it without specialised filters – it could blind you.

Techniques

Wide field

Just a camera & lens can be used to take a broad picture of the night sky. Short exposures can be made on a tripod but longer exposures will need some sort of tracking mount. This can be as simple as a ‘barn door mount’ (search the web for plans on how to construct this for about £15) but is frequently done by ‘Piggybacking’ your camera on a telescope & mount whilst tracking. This requirement to track the sky for exposures above a handful of seconds is common to all astrophotography where you don’t wish to see the effects of Earth rotating.

Afocal

Your telescope is all set-up and you’re viewing an interesting site through the eyepiece, the simplest way of recording this is t
o hold your digicam to the eyepiece & take a picture. There are things that you can do to refine this:

· Buy a digiscoping adapter to firmly hold your digicam to the eyepiece ~£30

· Match your camera lens to a suitable widefield eyepiece, specialist ones are available

· Set your digicam’s aperture wide open

· Use your digicam’s manual focus, set it to infinity & focus with the telescope

· Use a remote release or your digicam’s internal timer – avoid vibrations

Most of all experiment with different settings & targets, get to know what effect each change makes and have fun.

Prime

This is the main technique for serious astrophotography. The telescope is all set-up and the camera is attached via an adapter directly to the telescope. There is no camera lens between scope & camera; the telescope focuses light directly on to the camera’s sensor or film. The camera itself may be a SLR (Digital or Film), a specialist cooled astronomy CCD, or in some cases a webcam type video camera.

   A collection of Messier objects

SLR

Most people would accept that the Digital SLR now has an advantage over film. You will need a ‘T’ adapter for your camera make, to attach it to the scope camera adapter. You will also need a remote shutter release cable. The ability to connect the camera directly to a computer is also helpful. A 90 degree viewfinder attachment can also help to avoid the need for limbo dancing lessons. (That or a good osteopath). Focusing can be awkward – autofocus is unlikely to work for all but the brightest objects. It is best to find a bright star & focus on that, then leave the focus alone for the night if possible – do take a test shot to check your focus. There are computer programs that can help you with this. Also worth noting is that most standard cameras have an infra-red filter (needed for normal daylight photography) and this reduces their astronomical sensitivity. Only Canon have made a specialist astronomy DSLR, the 20Da, but several conversions are available, particularly by a company called Hutech.

Astro CCD

These devices are very sensitive to light; they are typically cooled to 20 degrees below ambient for noise reduction. They are however, very expensive & can only be used for this one purpose. At £1000 – £4000 this is definitely the hard core end of the hobby. They are controlled from a computer and can produce stunning images. Imaging is usually done by taking four sets of images using a filter wheel, 1 set for luminance & then 1 each for Red, Green & Blue; however ‘one shot colour’ CCD’s are available. Do not however under estimate what can be achieved with a DSLR.

Webcam/Video

This is a relatively new technique and is especially suited to planetary imaging. A short spell of video, perhaps 1000 frames, is recorded straight to PC. Each frame is then analysed by a computer program and the best are stacked together to build a detailed image. The advantage of this is that moments of good ‘seeing’ (I.e. when the atmosphere is still) can be caught and used, whilst more ‘wobbly’ moments can be discarded. The standard software for analysis & stacking is called Registax. You can build your own camera or buy a commercial one such as Celestron’s Neximage (about £90).

CCD / DSLR Processing

Typically when imaging a deep space object (DSO), you will be taking multiple exposures of the object. These exposures are called lights and they will be stacked together in a computer to create a far more detailed image. You should also be taking exposures called darks & flats. Darks are taken at the same temperature & settings as your lights, these will be used to correct the lights for hot pixels & circuit noise. Flats are taken at the lowest ISO setting of your camera and are of an evenly illuminated object, a lightbox or the evening sky just after sunset. These flats are used to correct your lights for vignetting and dirt on the imaging train. You should also take darks for the flats, no I’m not kidding! There’s various software available to help you with this process some commercial some freeware, Deep Sky Stacker is an easy start but my preference is for Iris.

Telescopes

I am not going to go into telescope choice very deeply here, everyone has there own preference & budget. But there are a few pointers:

· Don’t buy a Department Store special, do buy a proper astronomical scope

· Refractors will give you stunning sharp images but they’re expensive per inch of aperture and you’ll want an APO version to keep colour issues to a minimum

· Newtonians are cheap for large apertures but don’t always convert into a photographic instrument without hitches

· Catadioptics are a large group that inhabit the middle ground and are my preference, there are different types:

o Maksutovs are good visual instruments but can be a bit slow for imaging

o Schmidt-Cassegrains are a good all round scope that won’t break the bank, this was our choice.

o Ritchey-Cretiens are the desire of many an astrophotographer. Not cheap but superb for imaging – this is the basic design of Hubble.

   6 inch SCT with piggybacked 400mm Canon lens – all on CG5 equatorial mount

Guiding

Sooner or later you may wish to take images that require an individual exposure time of more than a minute or two & a reasonably long focal length e.g. 1500mm or more. At this point the tracking of your telescope mount may not be accurate enough, now you need a guiding system as well. This will either manually or automatically correct the telescope position at short intervals, on top of the equatorial tracking. The details of this are many, definitely beyond the scope of this article but you should be aware that several methods exist and there are several interest groups on the internet that will be willing to advise you.

Summary

I have tried to give you a brief outline of Astrophotography. There are many wonders to see, they are inspiring, they put us into our proper perspective and they are beautiful. A telescope alone is a fantastic resource for any home educator, but add a camera to the plot and you will see many more beautiful wonders.

Resources:

Books:

Stardust Magic by Moonlight                                  Linda Chapman   ISBN 0141317795          Well, it inspired Tamsin

Starware                                                                     Philip Harrington   ISBN 0471418064          A guide to all the kit

Digital A
strophotography The State of the Art   David Ratledge      ISBN 1852337346          You really need this book

Stars & Planets                                                          Ian Ridpath            ISBN 0751327123          Finding your way around

Astronomy for Dummies                                         Stephen Maran      ISBN 0764584650          A crash course in the basics

What are you waiting for? Go put your head in the clouds.

Now that 17P/Holmes is developing something of a tail, I’ve been keen to get a deeper image than that of a few nights ago (that showed the core & initial coma only). Whilst having our Guy Faulkes night bonfire, the skies cleared out. So after some family comet viewing through the C6, I changed for my 400mm Canon lens & started imaging. The skies clouded over again at about 1am 06/11/07 UST, by then I had captured almost 4 hours of exposures, here’s the image …

  Click image for larger view …

This image shows the Comet, from the core, right through its layers of coma and out to the tail, which is now developing beautifully. The image uses different length exposures to capture details with vastly different luminosity, as detailed below:

 8 x 30s           240
 1 x 90s             90
15 x 121s     1815
75 x 151s   11325
 3 x 242s         726

This gives a total integration time of 3 hours 56 minutes & 36 seconds. Software used to stack & process the subs, included: Iris, PixInsight, Image Analyzer, Photoshop & Lightroom. Different processings of the data were undertaken and these were amalgamated via layering in Photoshop. Initial processing in Iris included correction with 10 flats, 5 flat darks & 15 darks; the corrected & stacked images were binned 2×2 in Iris before output to PixInsight.

On a note of scale, the diameter of this comet’s coma is now reported to exceed that of the Moon’s orbit around the Earth. In contrast, the actual solid comet core is only a little over 3 kilometers across.

On 24th October this year (2007), Comet 17P/Holmes showed a rapid increase in magnitude. Often quoted as a mag 17 object, this comet brightened to magnitude 7 during the one night. By the end of October the comet was quoted as magnitude 2.5.

Throughout that time the clouds at my home remained steadfast in their determination to block the view but for just 1 hour last night they broke allowing a truly magnificent view of this comet. After enjoying the view visually, I had just enough time to grab a few frames with the 20D, here’s the resulting image …

  Click image for larger view …

Did you know that the name ‘Comet’ comes from the ancient Greek description of these objects “aster kometes” or long haired star! At the time of my image above, 17P/Holmes was calculated to be 1.621au from Earth. The image shows both core and some coma of 17P/Holmes. Any tail would currently be pointing pretty much away from earth and therefore be difficult to observe. The coma of a comet is often made up of ice & dust that has been super heated whilst the comet passed by the sun; any tail is formed of particles that are pushed away from the comet by the pressure of light from the sun. This Comet was discovered by Edwin Holmes in 1892, during a lesser outburst. Plenty of additional scientific data is available on NASA’s site.

To view the Comet, you currently need to look at the constellation of Perseus, 17P/Holmes’ path is making a loop through Perseus & will remain there until spring next year. It is currently visible with the naked eye, binoculars or a small telescope will show more of the fuzzy details. For up to the moment co-ordinates download Cartes du Ciel & use the finder tool on 17P/Holmes.

Good viewing.

It’s still cloudy outside & likely to be so for some days yet, so here’s one I prepared earlier!

In between imaging Orion (in October), I took a quick widefield shot of the California Nebula.

Taken at 200mm whilst waiting for my main target of the night to rise into a suitable position, there’s 1hr 20mins of exposure at f5 ISO1600.

The California Nebula is about 1000 light years away & appears in the constellation of Perseus. It is designated as NGC 1499, a low brightness emission nebula. The nebula is of considerable size & is probably illuminated by Menkib (bright star beneath nebula in my image).

Orion is a large & fascinating constellation, it graces our northern skies through the winter months. This is a brief journey through some of its sights, please click on any of the images in this article, to see a larger more detailed version of that picture. The majority of my imaging time for the last month has gone into this, so I’ll start with the view that you might see with the naked eye & progress through to close-ups of some of the more striking nebulae.

The image above left is what can be seen with the naked eye at a relatively dark site. Orion was “The Hunter” in Greek mythology, there are various tales about him, the most common explanation for his place in the sky is as follows:

Orion, son of Poseidon, loved Merope, one of Atlas’ daughters, as immortalised in M45 Pleiades. Merope did not love Orion and so he wandered the countryside, hunting animals. One day he was fatally injured after stepping on Scorpius, the Scorpion. In his memory, the Gods placed him in the sky, as far from Scorpius as possible. As company, they put his 2 hunting dogs Canis Major & Canis Minor with him. As quarries in the hunt, Lepus the hare & Taurus the bull are also within his region. They all stand by the river, Eridanus. An alternative story has similar details but suggests that the goddess Artemis was tricked into killing him and so created his constellation in her grief. Whichever story one goes by, Orion still chases Merope & the other Pleiades across the night sky – an eternal love story.

If you view the 2nd image, above right, you will see the outline of Orion. He is classically posed, half kneeling to aim his bow, which he holds in front of himself with his left arm. His right arm swings a weapon up above his head. Meanwhile from his belt hangs his sword, dominated by the beautiful nebula M42. The star name Betelgeuse comes from the Arabic for “The armpit”.

 Following on from the above 2 images, we’ll now close in upon Orion’s body bounded by Betelgeuse & Rigel (below left image) and further in to the stunning region around Orion’s Belt (below right image) …

Note how many stars appear as we increase the total exposure time. One of these stars HR1988, located about 1/3 of the way from Alnitak to Betelgeuse, has at least one possibly two planets in orbit around it. HR1988 is a magnitude 5.95 star with a spectral class of G4V. Other stars of note are Saiph & Rigel (knee & toe), Betelgeuse & Bellatrix (shoulders), Meissa (head) and Alnitak, Alnilam, Mintaka (belt). Details as in the table below:

The image ‘Orion’s Belt 105mm’ above right, concentrates on the Belt region. The belt asterism is formed, as mentioned above, by Alnitak, Alnilam & Mintaka. To one side of Alnitak there is the Flame nebula & at right angles to this, the Horsehead Nebula. Orion’s Messier objects are also shown, read on below for more details.

So time to take a look at some of the nebulae within Orion. There are 3 Messier objects within Orion – M42 the Orion Nebula, M43 De Marian’s Nebula and M78. The image below shows M42 & M43 along with their immediate neighbours.

  Click image for larger view …

M42 The Great Orion Nebula is the large pale blue and red nebula just right of centre. The small circular red nebula with a dust column rising in front of it, that is M43. To the left is NGC1977, the Running Man and fully to the left is NGC1981 an open cluster of stars. Deep within the base of M42 lies the Trapezium cluster, click on the image above to view the larger version and pick out some of the Trapezium stars. The M42 nebula is the closest known place of star birth to our solar system. Hubble Space Telescope has not only identified star birth there but also the formation of proto-planetary discs – that from which planets of solar systems are born.

The image below is my first of the other Messier in Orion, M78. I was plagued with high level cloud whilst trying to image it. The result of this is that I currently have less than half my planned exposure time, I will have to revisit when the weather improves.

Click image for larger view …

The M78 image does show the blue star light from the reflection nebula, also appearing are the clouds of interstellar dust that lie across the region. These should become more evident in a longer exposure. This is another area of young hot blue stars. In the top left corner of the image lies NGC2071 a similar & related object.

All the above nebula objects are part of the Orion Molecular Cloud Complex. This huge cloud is about 1600 light years away. The entire complex comprises dark, reflection & emission nebulae and is the birthplace of many stars. Also included in this cloud are Barnard’s Loop and my current favourite region of the night sky – The Horsehead & Flame Nebulas.

Below is my recent image of the Horsehead region …

Click image for larger view …

For more details on this image and the region, please see my previous Horsehead article.

**Update Mar08: For further info, view my post about Barnard’s Loop in Orion**

and/or view the image below:

  Click image for a larger view …

Useful Coordinates:

ID Name RA Dec

NGC2024    Flame Nebula    05:41:42 -01:51:00
M78              NGC2068          05:46:45 +00:04:48
M42     Great Orion Nebula  05:35:16 -05:23:25
M43     De Marian’s Nebula  05:35:31 -05:16:03
B33       Horsehead Nebula   05:40:54 -02:28:00

Further Info:

Betelgeuse is a huge red super giant.

Rigel is a Blue super giant and whilst much smaller than Betelgeuse it is still almost 100 times the size of our Sun.

Orion has been known as a constellation since ancient times though by different names in different cultures. It was Osiris to the ancient Egyptians, Al Jabbar to the ancient Arabs, a Shepherd & Sheep to the Sumerians and part of the White Tiger to the Chinese.

An interesting article about Orion’s potential interest to ancient Britons may be found here.

For more on the Greek Mythology, why not investigate the widget below:�

I hope this article has been useful & interesting to you, it’s certainly been fun in the making

Come back through the autumn/winter for a return to M78 & maybe some deeper region images too.

-

IceRocket tags: Orion, Constellations, AstroPhotography, Guides

NGC 891 is found within the constellation of Andromeda. It is a beautiful barred spiral galaxy that we view from side on. This galaxy has a Magnitude of about 10 but a surface brightness of only 13.6. With only 6 inches of aperture and imaging at f10, it was tricky to raise any details up out of the background noise; I am however quite pleased with the resulting image (below) and feel that gaining more exposure time would help further.

  Click image for larger view …

The galaxy was discovered by William Herschel in 1784 and is a member of the small NGC1023 group of galaxies that are neighbours of our own galaxy group. Its distance from ourselves is thought to be about 10 million light years. NGC 891 has several distinct similarities with our own Milky Way Galaxy, in fact it gives us a glimpse of how our galaxy might look to some distant galactic traveler.

The Horsehead Nebula is located in the constellation of Orion, close to the supergiant binary Alnitak or Zeta Orionis. Orion & its molecular cloud is one of my favourite parts of the sky; so I am currently enjoying imaging this region. The second half of last week proved quite suitable to long imaging projects. The midweek nights had been misty but the early hours of 5th & 6th October allowed me to capture some subs of the Horsehead. Currently Alnitak rises above my horizon in the SE at 3-30am and the sky becomes too light for DSO imaging around 6am, so that limits imaging time. Over these 2 mornings I did manage to collect 4.25 hours of decent exposures – here’s the result:

  Click image for larger view …

The subs were shot using a Canon 20D & 100-400L lens @ 400mm f5.6 ISO1600. The best 170 sub exposures were used to create the total exposure time as above. 23 Darks, 7 Flats & 2 Flat Darks were used to preprocess the lights; meaning that it took over 200 exposures to create this image, the most I’ve used so far. This equated to problems. I run Windows Vista which I have found to be better at memory management then previous Windows versions and my PC is a reasonable spec as follows: AMD dual core processor, 2GB Ram, 2Gb ReadyBoost Memory, 2GB DiskCache, 2/3 Tb Drive Space. Yet despite this there were issues with using adaptive stacking techniques in Iris; admittedly this did involve over 6Gb of data but it still caught me by surprise – result was that I had to use simpler additive stacking techniques in Iris, oh well!

Anyway back to the Astronomy. This region of Orion has several interesting named structures, the version of the image below is annotated to name the most prominent ones:

Click image for larger view …

The Horsehead (Barnard 33) is an amazing structure of dusty clouds & stellar birth, it was voted in 2000 as the object that people most wished Hubble Space Telescope to be targeted at. We can only see B33 because it is illuminated by the bright nebula IC434 which lies immediately beyond it; both are about 1600 light years from Earth but still located within the Orion arm of our own galaxy, the Milky Way. At the base of B33 lies NGC 2023, this is an emission nebula. The star at its centre is very young & hot it is pushing a space for itself & ionising gas in its locality, hence the classic pale blue emission colour. IC 431 432 & 435 are similar nebulae wrapped around their respective star sources. All the remaining labeled items, save one, are key stars of the region.

NGC 2024, the Flame Nebula, is the remaining object. The Flame Nebula is also some 1500 – 1600 light years distant and part of the Orion Molecular Cloud Complex. Conventional wisdom was that the source of ionising radiation that illuminates the hydrogen gas of the nebula was Alnitak. However recent measurements of Alnitak put it at only 800 light years distant, therefore not the source. Most likely there is another young super hot star hidden behind the thick black dust lanes that are in front of the Flame Nebula (see link for evidence).

  Here’s a closer look at B33 from my imaging.

From nose to mane is a region just  over 2 light years in width; this is one enormous horsey dust cloud.

This whole region is a mass of star formation, dusts & gases; the red nebulosity above IC 434 is mainly due to high energy ionised particles being flung out into space like some grand cosmic fountain. It is a truly fantastic sight. I plan to continue imaging in & around Orion during the next few weeks / months and to post an overview of this constellation. As ever I shall be limited by the weather and my depleted sleep schedule,  zzz zzz zzz …

 You can read / view more about Hubble’s image of the Horsehead at the HubbleSite. The image was a 4.6 hour exposure for Hubble.

In these modern times, we have become rather profligate with our lighting. Yes a bit of light to read or work by is beneficial but do we really need to light up our whole planet like some over decorated Christmas tree! There seems to be a common held belief that high levels of external lighting will improve safety and reduce crime; yet there is very little evidence to support this. If light is genuinely required then it should be used sparingly & only be directed where needed, not left to pollute a large area. There are various good reasons to control light pollution, here are just a few:

• Creating light costs energy, wasting energy is environmentally unfriendly
• Broad light pollution can confuse & maybe harm wildlife
• Lack of proper darkness disrupts the natural rhythm of human life and can lead to illness & an inability to sleep
• A complete generation of city dwelling children are growing up without seeing the beauty of our night skies
• Besides anything else, give your eyes a few minutes and its amazing how much you can see in the dark.

I’m lucky to live in one of the darkest areas of the UK with magnitude 5 – 6 skies, great for wildlife & great for astronomy. BUT even here there are a few street lights across in the village, not many but a handful. I can often avoid them during astrophotography sessions; they’re at least half a mile away behind my house & some trees. However I want to illustrate just how damaging even a few lights can be, here is a picture from the other night:

  Click image for larger view – Canon 300D 10mm f3.5 49secs

It was taken at almost 2am, long after the street lights are needed for anything. The night was basically clear at high levels with mountain cloud & valley mist drifting in and out. There was a partial moon so the high night sky wasn’t as dark as it can get but the village lights are dominating the scene with their orange glow. If that’s from a few lights imagine what an entire city of lights can cause.

What can you do about this? Well try not to use ‘flood’ type lighting unless you really need it. Use outdoor lighting that only throws light downwards to where its needed. Ask your local authority to minimise the use of wasteful street lighting. Join a campaign for dark skies. And more immediately …

You can carry out a survey on how dark your local night skies are. We were part of the UK specific survey earlier this year. Now Ed over at Flintstone Stargazing has kindly pointed out that there is an International Survey taking place and we can all take part in this project, so why not head over there and take a look, it closes on 15th October.

I’m still learning, in fact I hope I always will be. However, I think this may be a good point in my journey to put down some details so that others who are starting out on this fascinating path can pick up a few pointers & ideas. There are some excellent tutorials out there and I’m not going to compete with them; rather I’m going to tell the story of my recent M31 Andromeda image, with a few extra details.

Imaging Aims –  My aim when taking this image was to produce a sharp image with a realistic hue. The image should show the extent & detail of the galaxy with dark dust lanes, star clouds & globular clusters. The core of the galaxy should not be too burnt out and the image should successfully print out at A4+ for framing. Here’s a reduced sized version of the final image (in case you didn’t see my Andromeda post) :

  Click image for a larger view

Equipment -  Everything should start with a solid basis and never is that truer than in Astrophotography. A solid tripod or pier with a decent mount atop is the prerequisite for any imaging of DSO’s (Deep Space Objects). The mount will need to ‘track’ the sky ie counteract the rotation of our planet. On this mount will be your imaging system, a camera & lens system. The camera maybe a simple compact digital affair, a webcam, an SLR or a specialised astro CCD. The lens system may be a variety of telescopes or even quality camera lenses. Computerised control systems can also be added; as can guidance systems that greatly improve your ability to take long exposures. Discussions about equipment can be found elsewhere; suffice to say that I mainly use a Celestron AS-GT mount, Canon 20D camera and either a Celestron 6 inch SCT or a selection of Canon lenses. I have no guiding system at present. For this image I used the 20D with a Canon 100-400 L IS lens set at 300mm f5.6 and mounted directly on the AS-GT.

  Mount, Scope & Camera with Lens

Technique – The basic technique employed here & for many astrophotos is to take many short sub exposures and then stack them together to make the final detailed image. For an interesting discussion on short sub-exposures visit Samir Kharusi’s website. Put simply, the benefit of this is to drastically increase the signal to noise ratio of the final image whilst allowing the demands on tracking / guiding to be reduced. To illustrate the point I have done a simple unregistered luminance add of my 1.5 hrs worth of subs, this is what the image would look like without using a stacking procedure, see below …

  Not a pretty sight

Planning – Next we need to select our target, check that it will be visible for long enough and calculate what focal length will be best for the object; may I suggest AstroPlanner as an excellent piece of software for this purpose. To help general visualisation I would also suggest a Planetarium program such as the excellent freeware Carte du Ciel.

Set-up – As routine before imaging we should have aligned our mount to the celestial pole and adjusted the balance so that it is almost perfect but just a little heavy on the side pointing eastwards (this encourages the tracking to be slightly tighter).

Now we should pre-focus the camera on a suitable bright star; I’ve come to know Vega quite well, this summer. There are various automated computer programs to help but I currently use a visual diffraction focusing technique always followed by taking a test shot. This done we can now find & frame the object that we wish to image. The AS-GT mount has a very useful feature called ‘Precise Align’, if you have this mount then I recommend you use the function. With the object aligned take a test shot this will allow you to double check the framing of the object & to estimate the required camera settings.

Camera Settings – So what total exposure time do you need? What length sub exposures? And what ISO setting. Through trial & error I have found that ISO 1600 on the Canon 20D appears to suit my imaging best; ISO3200 gives a lot of noise but ISO800 gains me no quality improvement over 1600. Total exposure time – well looking at other astrophotos will give a good guide, experience has to help too and don’t forget to check out the magnitude of the object, if its available in a sky catalogue. As for sub-exposure time well I’m a little more scientific over that …  Your sub needs to be long enough that the fine details are recorded above the background noise level but not so long that your mount runs into significant tracking errors. Take a test exposure and review its histogram on either the camera back or a PC.

  The histogram for one of my M31 subs

If the histogram looks similar to the one above then your exposure should be fine, in general aim for the lefthand edge of the spike to be 1/3 to 1/2 of the way from the left of the histogram – this lifts the detail out of the noise zone without blowing the highlights. Now is the time to have a check for tracking issues, are the stars nicely round, if so then we’re ready to go!

Image Capture – We now can set the camera to work and allow it to accumulate the ‘lights’ that will make up your full exposure time. I find it useful to use Canons TC-80N3 programmable remote control, just tell the camera to take x many exposures y seconds apart and let it go. Now’s the time that you can go have a cup of coffee or two but do watch out for rain or any other problems. Alternatively, if you’re capturing to PC then you could give AstroScopius a go and watch as your image integrates in front of your very eyes!

As well as lights you need to capture dark frames & flats. Darks are simple, just put the lens cap on and shoot a few frames at all the same settings, including temperature, as the lights. These darks will be used to correct for hot pixels & noise. The flats should be taken at the lowest ISO setting possible and should be of an evenly illuminated white object I have successfully used the dawn sky, a lightbox and a magi-whiteboard with fluorescent strip light illumination. The histogram for flat
s should show a spike as far to the right as possible without overexposing anything.

  Histogram for the flat field

Looks like I had room to expose this flat a little further but it worked fine anyway. The flats will be used to correct for errors in the imaging train such as vignetting & dust bunnies. You will also hear of bias or offset images, these are used to correct for permanent sensor pattern issues but I have found it unnecessary to use more than a synthetic bias file, created at the processing stage.

So its now dawn, you’ve been up all night and what do you have to show for it? A bunch of light dark & flat files, none of which look like you’d wish the finished image to be. I had 45 lights of 2.5 minutes each (but I chose to discard 8 of them) 10 Darks 5 Flats & 5 Flat Darks. Examples below (Light, Flat, Dark) …

Click on the light file (left) to see an enlarged version.

 What to do now, my advice – get some sleep before starting processing

 Processing – There are many different methods & programs to process your raw images; here I shall give an overview of what I did for this image:

I have tried several different programs for the scientific initial processing, some pay some free, and have found none better than Iris. Whatever program you use, good image organisation is useful; with Iris it is vital. The program has a working directory where it will save all files including a copious amount of working files, probably several gigabytes worth. I use a striped drive (for speed) with a separate working folder for each project, as per the screen capture on the left. 

The next few stages are all done in Iris; if you are going to learn it then may I suggest reading the tutorials on Christian Buil’s site and for a detailed walk-through you will find Jim Solomon’s Cookbook an excellent resource. Here is the basic process:

• Discard any dodgy lights due to clouds, airplanes, etc.
• Import good RAW files
• Create master dark & flat files plus synthetic bias & cosmetic files
• Correct the lights by applying the darks, flats & bias to them.
• Register the files, so that stars are all aligned
• Crop out the edge overlap caused by aligning the files
• Normalise the files to equalise their background
• Stack the files to produce 1 file with all your data in it

At this point you could move on to another program or do some more processing in Iris. I did the latter, first correcting the white balance, using sub 1 ratios to avoid burning out any highlights, typically the ratios are 0.98R 0.50G 0.63B when I’ve used the 20D. I then experimented with both dynamic & colour stretches, finally deciding upon a relatively moderate asinh colour stretch. Final things in Iris were to adjust the visualisation and save my output to file – in this case a full depth bitmap file.

Next I moved into PixInsight which is convenient because it reads the full depth of an image produced by Iris without needing to adjust the levels as would be required in Photoshop. There is a significant overlap in functionality between Iris & PixInsight and while I prefer to use Iris for most things, there are a few functions that I am, so far, better at using in PixInsight. These include the two that I used here:

• HDRWavelet Transform to extract high dynamic range data within the galaxy, in this case it took 2 transforms one of 4 iterations & the next a single iteration. The output was rather too harsh for my liking so it was blended with the original in Photoshop.
• Finally a morphological transform to control the distracting starfield between us and the target. Again this was layered and blended using a mask in Photoshop so as to maintain clarity of the globular clusters within Andromeda.

The resulting layer blends were finally flattened in Photoshop before export as a 16bit Photoshop file. The final stage for all my images, astronomical or not,  is in Lightroom. Clarity, Vibrance, Curves, Colour Temperature and more can all be fine tuned losslessly in Lightroom. Not to mention it is efficient at outputting to 8bit jpg for posting on the web. In this case I needed to do very few final tweaks (minimal clarity & sharpening) and the image is as at the head of this post.

I should point out that this is an overview of the processing that I did – in reality the image & processing evolved over the course of a fortnight as I tried out new ideas. Sometimes I’d leave the image open on my desktop so that I could glance at it & think “hmm, I’ve not quite got x right” and so forth. I think that’s the thing this should be a fun adventure and one of learning too – no rush, no competition just fun learning.

I hope that this post will help a few people who are starting out, to be able to take a step forward with their imaging; it has definitely been useful to write.

I recently decided to revisit the beautiful planetary nebula that is M27. The plan was to start from scratch, collect several hours of exposure and create a very deep image. However the fates conspired against me – for once my weather forecasting info was inaccurate and heavy cloud came in after only 30 minutes of exposure. However there is little point in arguing with the weather, so I gladly took what I had and combined it with my previous 17 minutes of data from late July.

  Click on image for a larger view …

I’m quite pleased with the outcome but would still like to do a several hour exposure some time.

  Click on image for a larger view …

As usual, here’s my Messier Infocard for the object.

I know that I keep telling myself not to attempt deep red nebulae until I have a modified camera but I just can’t help it, I love the deep red Hydrogen emission colours and the mysterious shapes that these nebulae form. Anyway, earlier this month I noticed that NGC7380 (in the constellation Cepheus) was placed nicely for a photo; my resolve broke and I thought the worst thing out “I’ll just spend a little time taking some test shots”. Inevitably this leads to insufficient integration time especially when I should be extending the time on an object in this wavelength region. There you go, a little over 1hr 10mins of exposure later & I’ve set myself a processing challenge

  Click on image for a larger view.

I’ve been playing with the processing on & off for over 2 weeks but the image above is what I’ve now settled upon. Details as follows:

Imaging info: Canon 20D C6SGT Prime f10 ISO1600 Exposure 1hrs 10.25 mins in 31 subs

Processing Info: flat & dark correction, stacked, aligned, colour balanced, asinh stretch all in Iris  -  levels adjustment in Photoshop  -  noise control & enhancement in Pixinsight & PureImage  -  final balancing & clarity in Lightroom.

I know that there’s more to be had from this nebula and I shall return in the future but for now it has provided me with a fun challenge that has allowed me to learn more useful processing skills.

 NGC7380 is in fact an open cluster of stars with associated nebulosity. It is thought to be 7-10 thousand light years away and was discovered by William Herschel’s sister Caroline. It is sometimes called “The Wizard”  – imagine a pointy hat & beneath it a wizard throwing out his hands to cast a myriad of spells.

Last night was the first frost of the autumn for us; so naturally I stayed out getting cold all night. I had a list of Messier clusters that I wanted to see but apart from that I was also hoping to get a glimpse of M42 & M43 in Orion. It’s really too early in the autumn for viewing Orion from here, the height of our mountain horizon is such that Orion’s belt is just creeping above the forestry as morning twilight dawns. Never the less its nice to see a long lost friend.

All frosty & misty

 at home this morning.

 Orion rises above the forestry,

 as the misty dawn sky starts to lighten.

As you can see, morning was accompanied by significant levels of valley mist and the night had been punctuated with skimming clouds & showers. Transparency wasn’t to bad in between times though. So as 4-30am turned into 5am I swapped the SCT off the mount, in favour for my 400mm Canon. A few pressured minutes focusing & aligning on Orion left me with just enough time to fire off a handful of 45 second exposures in the ever lightening sky. Shoot some darks and some flats, then time for breakfast. I haven’t processed my cluster data yet but I’ve rushed out the Orion data. The image below shows: M42 (The Great Orion Nebula or NGC 1976) – M43 (de Marian’s Nebula or NGC 1982) – NGC 1977 (The Running Man) – NGC 1981 (Open Cluster) – plus a variety of Orion’s beautiful coloured background stars.

  Click image for larger view

Messier 42 & its neighboring DSOs are all located a little below Orion’s belt and a good pair of binoculars is all that is needed to start enjoying this view. I hope to return to image Orion in further detail at the end of the year when the brave hunter is higher in the northern skies and I can perhaps gain more than just the 8 minutes 45 seconds of exposure that was used in the image above. For more details and an example of what can be gleaned from one short exposure have a look at my Messier info card for M42, below:

  Click image for larger view

Probably one of the most viewed Messier objects, M42 was first discovered by a Mr Fabri de Peiresc in 1610. Galileo studied the region shortly afterwards and discovered the Trapezium star cluster that is embedded within M42. The region is one of star birth, where dust & gas aggregates together to form new stars & perhaps planets too. The red colouration is due to ionised hydrogen (H alpha emissions) whilst the blue-mauve colours are due to large type O stars that illuminate the surrounding dust. There is also a slight green tinge and this is due to the ionisation of Oxygen. The final image below was binned 2×2 and given aggressive processing to emphasise the gas ionisation colours & dust clouds.

  Click image for a larger view

If you would like to learn more about this fabulous nebula, may I recommend the excellent article on the Wikipedia.

So I’ve imaged Andromeda with a 105mm focal length lens and Andromeda’s core with an SCT & reducer at 945mm, but now it’s time to keep my promise to myself and return with the 100 – 400 L lens, seeking a detailed full frame image. No piggybacking this time just the camera & lens attached to the  AS-GT mount, 2.5 minute subs & a over 1.5 hours of exposure:

    Click on image for a larger view

The expanded image (click above) is still significantly reduced & compressed to make it web suitable but I hope it conveys what a fascinating object Andromeda is.

At 2.9 million light years distant & 250,000 light years in diameter, Andromeda is the largest galaxy in our local group of galaxies, though some recent research suggests that our own Milky Way probably has more mass.  This image also shows her 2 main companion galaxies, the oval M110 below and the apparently more rounded M32 above. Both companions are in fact dwarf elliptical galaxies. Andromeda is another deep sky object that has been known since ancient times with definite observations having been noted by Persian astronomers prior to 1000 AD. For a few details have a look at my Messier Info board below:

Click on image for a larger view

Andromeda contains billions of stars and many structures that we observe in our own galaxy (e.g. Clusters, Nebulas, Planetary Nebs, etc.), they have also been studied in M31. One such structure is NGC 206 the ‘Star cloud in Andromeda’ which The Sky describes as Cluster+Nebulosity. Looking at my main picture above it is located as a lighter patch amongst the dust lanes, towards bottom left of the galaxy. Here is a close crop of the region:

The lighter patch in the centre is NGC206, it is thought to lie at the intersection of 2 spiral arms and is probably the greatest region of star formation within our local galaxy group. M24 the Sagittarius Star cloud is a similar but smaller structure in our own galaxy. You can also see many globular clusters in my main image of Andromeda, they appear as lighter ‘specks’ embedded within the galactic structure.

As for companion galaxies in excess of M32 & M110 there are also NGC 147 & NGC 185 (further out and not in the image frame) and probably also the extremely feint systems named And I to XIV. Tracking down some of these other companions and the galaxies of the local group as a whole, well it looks like a substantial project & definitely one for another post.

 I must add that Tamsin helped find & frame this image before going to bed and allowing me to capture the subs. Andromeda is one of her favourite night sky objects – along with Regulus & the Big Dipper.

For those of you who use AstroPlanner, I have created a downloadable plan details as follows:

“Galaxies discovered to be in our Local Group as of 2007. Data not in catalogues (unknown ID) has been added from various internet sources  – therefore please consider this as a beta version. User field 1 suggests good starting points for N.Hemisphere imaging. Please post comments/corrections to Yahoo group or via my website http://www.annmariejones.me.uk thanks.”

If you don’t use AstroPlanner then I do highly recommend it as a brilliant program and great value too.

Click below to download from here or download via the ‘User contributed plans’ menu in AstroPlanner.

• Local Group Galaxies Plan - AstroPlanner Format (txt)
• Local Group Galaxies Plan – Nextour Format (hct)

Well during most of the recent clear nights I’ve been working on imaging M31 via different setups (see other posts) but late last night the Pleiades were comfortably above the mountain horizon and so I decided to take a shot at capturing this beautiful open cluster. I’d been imaging with the Canon 100-400 L IS on my 20D, so that was what I continued to use – probably my choice for M45 anyway.

Maybe nearly 2am isn’t the ideal time to start such a project (if you want to sleep) but there we go. The mountain weather decided to play games with me, clouds rolling in and out  and having decided upon ISO 800 as a compromise to allow finer detail to show through I knew that I needed a minimum of about 1 1/2 hours exposure. I was still collecting data as dawn arrived; after sorting through everything I decided upon the 43 best subs, giving me almost my desired exposure time. In the clear moments conditions were as follows: Light breeze, Transparency Average to Good, Seeing Fair. You can always look at my weather station to get more general weather details. Here’s the processed image:

  Click image for a larger view …

(update) – During October I had the opportunity to re-image M45. On this occasion I made a much deeper exposure using ISO1600 for nearly four & a half hours of exposure – this allowed for a different processing and shows significantly more nebulosity whilst controlling the stars. Note how the nebulosity below Merope is not as intensely blue as the other nebulosity; there has been suggestion that this layer of dust has fewer hot blue stars in its vicinity, hence the change in hue. I prefer the long exposure image, you can see it below …

  Click image for a larger view …

The Pleiades or Messier 45 have been known since ancient times, with clear references to them in ancient Greek literature. They go under various names in different cultures around the world:

• Messier 45
• Pleiades
• Severn Sisters
• Subaru
• Matariki
• Also bees, hens and probably a few more too! I’m sure the Wiki article will list many more.

The image below is my usual Messier information board, click it to see a larger version:

The standout feature of this cluster is its nebulosity. It is a reflection nebula; a dust cloud, that is unrelated to the star cluster, is reflecting light from the cluster’s hot blue stars. This can be seen when carefully viewed through reasonable equipment but it really shows itself in long exposure photographs.

As I’ve mentioned already, the cluster is sometimes called the ‘Severn Sisters’, this name is derived from Greek Mythology where Atlas & Pleione had seven daughters, the bright stars of this open cluster are named after this family as labeled in the image below.

  Click to see the larger version

All in all definitely a sight worth seeing; and photographing.

My idea for this post is to illustrate that it is very possible to image interesting objects in the night sky, without the use of a telescope or an especially long focal length lens.

Our large neighboring galaxy M31 Andromeda is a good example, this galaxy can be made out with the naked eye, though you won’t be seeing many details that way! I’m going to use my Canon 20D here and yes I could use a big 400mm lens but that would rather defeat the object so here’s the list of kit used:

• Canon 20D
• Canon 24 – 105 L f4 IS
• Canon programmable remote timer trigger TC-80N3
• Celestron CG5 equatorial mount

So yes I have used one specialist piece of kit, the mount, but that really is necessary to track the sky due to earth’s rotation during the exposure time; no guiding system has been used though. The lens will be set at 105mm & wide open at f4; manual focus set and IS turned off. The camera was pre focused visually on a bright star and then the mount slewed to point at Andromeda. Whilst I used mains power for the 20D & recorded images straight to PC, this would still have been possible with a freshly charged battery & a decent compact flash card. The image below is the full frame output after processing (reduced in size of course) :

  Click on image to see larger version …

A total exposure time of 1hr 15mins was achieved by taking 37 separate frames, ISO was set to 1600. As well as these light frames, multiple dark & flat frames were taken. Darks are taken at the same settings & temperature as the lights but with the lens cap on, they are used to correct for hot pixels & noise. Flats are taken with the same zoom & focus as the lights but are at low ISO and are of an evenly lit object e.g. a whiteboard; they are used to correct for dust bunnies & vignetting. All of these images are put together in an excellent piece of freeware called Iris.

The output is then adjusted for contrast & levels in Adobe Photoshop before final output. Below is a crop into Andromeda herself.

  Click on image to see larger version …

As you can see, some of the dust lanes within Andromeda are very clear, the oval & circular bright patches above & below Andromeda are companion galaxies M32 & M110. So there we have it 3 galaxies, 1 picture and a focal length of only 105mm. “Size matters” or so they say but I’m not too sure

Why not have a go at a few photos yourself, it’s great fun.

Well, I didn’t stay away from Cygnus for long! To be honest I had some scope time to spare whilst trying out my new hyper-expensive techno gismo. I jest, it’s a diffraction focusing device to help me get the imaging just so. Take one homemade dew shield (tube of photo mount board plus tank tape) add 4 small holes, 90 degrees apart, as close to the telescope end as possible. Now thread 2 long fine knitting needles (thank you Jane) through holes so that they are at right angles to each other & thus form a cross at the front of the telescope. Now when you try to focus the telescope for the camera (i.e. looking through DSLR viewfinder) it is much easier since bright diffraction spikes appear when focus is reached. See picture below:

 Click image for a larger view.

This is Sadr, a beautiful star at the centre of Cygnus. Normally once all properly focused you would gently remove the knitting needles before imaging, but I felt like experimenting with the effect, so in they stayed. Now if we look at the full image after processing …

 Again click image for a larger view.

..you can see that much of the area around Sadr displays significant nebulosity. Imaging Details: Canon 20D C6SGT Prime f10 ISO1600 Exposure 44 mins 16s in 16 subs

So what is ‘Diffraction’ anyway? To quote GCSE Physics sources, “Diffraction is the spreading out of waves when they pass though a gap or around an object”; a little crude but that is essentially it. Light can be thought of as either a particle (photons) or a wave form i.e. it has duality. If you consider a wave front of light as it approaches a small ‘gap’ such as a diffraction grating or the ridges & troughs on the back of one of your music CDs; flat parallel waves of light may approach but waves that are curving appear from the other side of the gap. If there is more than one ‘gap’ then these curved waves can interfere with each other and this causes the colours that you see when looking at a CD or DVD surface. This same principle applies to my two knitting needles – parallel light from the stars curves (diffracts) around the needles, these resulting waves interfere with each other, producing a pattern that helps me focus. There are loads of uses for this, holographic imaging for one, analysing crystal structure is another; it is also the limiting factor for focusing good quality telescopes & cameras, see Airy Disc.

Later this month (night of Sept 9th), Uranus reaches the point in her orbit where she is at opposition to the sun (as seen from Earth), that is Earth & Uranus are closest together. The planet is currently positioned to also show 99.99% of her disc; and she’ll reach equinox early this winter. It is therefore a good time for viewing. I took both of the following images on the night 3rd/4th September ’07.

  Exposure 1second @ ISO400 – Canon 20D

Uranus is a gas giant in our outer solar system. Uranus is the seventh planet from the Sun & 3rd largest in our solar system. It is extremely cold (-215C) & is probably more similar in core chemistry to Neptune who lies beyond her, than Jupiter or Saturn who are closer to the us. Uranus’ atmosphere contains clouds of frozen water, ammonia & methane, these give the planet her blue/green appearance.

  Click image for a larger view …

The image above has a total exposure time of 3mins 45secs, it was awkward to control the over-exposure of the planet whilst picking up her moons. I have spent considerable time viewing star charts & working out orientation (as marked on the image) but I still have no idea what the object/mark in the western corner is (As normal, suggestions & constructive comments are welcome). Sky & Telescope have various useful write ups on viewing Uranus & an excellent JavaScript for identifying the moons at any given time.

I do enjoy imaging Planetary Nebula, they are such beautiful colourful objects. This one, the Owl Nebula, is thought to have formed 6000 years ago and as ever, it is the result of a star ‘blowing off’ its outer layer. The central star in the nebula is magnitude 16 & has a mass slightly less than 3/4 of our own sun.

Click on the image above to see more images & details

This nebulas’ structure is not fully understood and even its distance is debated.

In a pushed version of the original image it is possible to just make out several distant & faint background galaxies. Imaging this last night was a lucky bonus, I had not expected the skies to clear properly & was spending a little time tweaking the mount’s polar alignment. The skies did clear pretty well & despite a bright half moon, it was possible to image in the Ursa Major region for the first half of the night. This image was based around 2min 45s sub exposures on the Canon 20D at f10 & ISO1600. 50 lights, 20 darks, 20 flats & 10 flat darks were taken. Only 49 lights registered so total exposure time was a little over 2 1/4 hours. Still no guiding, so all in all I’m quite pleased with this one.

The other night (almost full moon), I thought I’d spend a relaxing evening having a look at a few clusters. Indeed I did, photographing M52, M56 & M71 in the process (see further below). Later on however my eye was drawn to the position of NGC 7635 “The Bubble Nebula”. Now I should have known better, full moon is not ideal for imaging nebulas, there was a cloud bank due to come in later and my unmodified DSLR isn’t very sensitive for picking up deep red nebulae. But heck, why let that stop me, so I took a shot at it …

Now I am not very happy with this image, it shows a desperate need for me to sort out some guiding (look for oblong stars). It also has insufficient contrast & resolution to be displayed as a larger image; this would be improved by increased exposure time and/or a camera more sensitive to its wavelengths. As it is this image has a total exposure time of 1 hour, sky conditions would not allow for more.

M52 “The Scorpion” an open cluster in Cassiopeia. (Canon 20D Prime f10 on C6SGT – ISO1600 15mins in 20 subs). Magnitude 7.3 and 5000 light years away. To see the shape, imagine a scorpion coming towards you, facing the bottom left corner, with its pincers out to its sides. Lying close to M52 is the interesting bubble nebula, as discussed above.

M56 a globular cluster in Lyra. (Canon 20D Prime f10 on C6SGT – ISO1600 15mins in 20 subs). Magnitude 8.3 and 33,000 light years away. Not the most spectacular of globular clusters but I don’t think I’ve enough clarity in this image, definitely one to re-visit.

M71 a loose globular cluster in Sagitta. (Canon 20D Prime f10 on C6SGT – ISO1600 15mins in 20 subs). Magnitude 8.2, 13,000 light years distant.