Sep 112015
 

Here are three different versions of M16, The Eagle Nebula in the constellation of Serpens Cauda. Interestingly, the constellation of Serpens is unique in that it is the only one that is split into two distinct pieces, namely Serpens Caput (the head) and Serpens Cauda (the tail). All of these images have been recently taken using the amazing telescope that I co-share with Australian amateur Jason Jennings. This scope is hosted in the iTelescope.net ‘barn’ at the Siding Spring Observatory, Coonabarabran, NSW, Australia. I’ll write another post about the scope soon, but it is an amazing 16″ f/3.5 astrograph.

This first version is a ‘traditional’ LRGB image, meaning it has been made by taking separate images using Clear (Luminance), Red, Green and Blue filters and then combining those to make a final colour image. This should be close to how the eye would perceive the colour because the R,G and B filters pass frequencies of light similar to the sensors in our tri-colour vision system. The clear filter is used as a luminance channel and is where most of the sharpened detail resides.

As with all the images, please click on them to see a full-sized version.

M16 LRGB Version

This next version is taken using three narrowband filters. These are H-Alpha (Ha), OIII and SII. The wavelength of these filters are commonly used by astronomers because there are a lot of emission nebulae that have excited atoms in them that emit light in these wavelengths (especially Ha which is nearly always the strongest). So, to produce an ‘RGB’ image from them requires that they are mapped to the Red, Green and Blue channels of the image. I have chosen to use the ‘Hubble Palette’ which maps the SII to Red, Ha to Green and OIII to Blue. Here is the result:

M16 Narrowband Version

You will notice that the star colours are not good in the narrowband version and this is a consequence of the filter mapping and also because of the relative strengths of the three channels. So, in the third image below, I have combined the stars from the RGB image with the nebulosity from the narrowband image. Here it is:

M16 – NB with RGB stars

I’m not sure which version I prefer!

Finally, a 4th image (I lied!) taken last year with a longer focal length instrument (12″ f/9 RCOS) which shows the ‘Pillars of Creation’ in more resolution. This was also taken using the Hubble Palette which is appropriate because the iconic pillars were made famous by those fabulous images from the Hubble telescope.

The heart of M16

 Posted by at 2:13 pm

Zooming in on The Ring Nebula

 Deep Sky, General Astronomy, Zoom in on ... series  Comments Off on Zooming in on The Ring Nebula
Aug 092013
 

What was it about The Ring Nebula (M57) that inspired me to put together this little blog article? I guess it must be that it was the first telescopic ‘deep-sky object’ that I ever learned how to find and observe . (I didn’t call them deep-sky objects back then and the brighter wonders such as the Andromeda Galaxy and the Orion Nebula which are visible to the naked eye don’t count! ) I remember using my 60mm Tasco refractor back in 1971, as an 11 year old to look at this lovely object, and was amazed by it. Within a few months I would see it in Patrick Moore’s 12″ Newtonian Reflector – well what can one say – incredible!

It was always likely to be M57 (out of many other objects) because it is really easy to find, located as it is between two stars in the ‘parallelogram’ of Lyra the lyre. Also, Lyra itself is easy to find because of its brightest star Vega, and the fact that Lyra is a compact constellation right next to it.

Before we go zooming in on M57, what exactly is it? It is a planetary nebula, so called because, at first glance,  it presents a planet-like disk to an observer through the telescope. However, instead of being at Solar System distances, it is roughly 2,500 light-years away and was formed when a dying red-giant star blew out its outer layers before becoming a white dwarf. Such a fate will probably befall our own Sun in about 5 billion years! Now, we see the remaining shell of ionised gas as it expands into the interstellar medium.

So, the idea behind this blog is to locate M57, and zoom into it using images that go from wide-angle camera shots to high resolution images from large telescopes. First, I’ll transport you back to my world of the early 1970’s by showing this scan from the wonderful star maps at the back of the classic Norton’s Star Atlas. I still reach for this book when I need to remind myself of various bits of the night sky! Here is the scan, I added the insert showing Lyra at a larger scale, but the map itself in very evocative to me, covered with the rubbed-out tracks of pencil-drawn trails from long-gone Perseid or April Lyrid meteors. You will see M57 indicated between the stars β (Beta) and γ (Gamma) Lyrae at the bottom of the parallelogram shape (which I have outlined).

 

Now, on to the first image. I took this back in early June this year using a Canon DSLR camera and an 18mm lens, giving a nice wide field view. (as with all these images – click on them to see them at full size, then click again to return). I have indicated a large green triangle which is known as The Summer Triangle consisting of the 3 bright stars Vega, Deneb and Altair. I have also annotated the cross shape of the constellation of Cygnus the Swan which is getting rather swamped by the Milky Way in this picture. You can see Lyra near the top.

 

The next image is only a bit more of a close up Lyra, taken with a 28mm lens this time. I have added the names of the two stars that straddle either side of the ring nebula. As you can see Beta Lyrae has the proper name of Sheliak, and Gamma is called Sulafat. Also annotated are a few of the other brighter stars in this field – Albireo is the head (or beak) star in the cross of the Swan. Many of the proper names of stars in use today come from an Arabic origin and Sulafat comes from the Arabic for ‘turtle’ or ‘tortoise’ as it seems that most fine harps (or lyres) were decorated in tortoiseshell.

 

So, let’s zoom in a bit further. Next I changed to a 50mm lens and have also added an insert to this image. The insert is at the full resolution of the image whereas the rest of the picture has been much reduced in size to get it on this page. Now we can actually see the Ring Nebula! It’s pretty small as you can see, in fact it is approximately 3.5′ (arc-minutes) across which is, roughly speaking, only one tenth the apparent diameter of the Moon. Note the use of the word ‘apparent’ there; The true size of M57 is some 3 light-years across!

 

Now the last camera shot, before moving to a ‘proper’ telescope (telephoto lenses are telescopes really, but you get the idea). This time, I used a 200mm lens and I have cropped out the Sheliak/Sulafet region. Now we can see the ring and can understand why this is known as a planetary nebula.  It certainly confused its discoverer. French astronomer Antoine Darquier de Pellepoix in January 1779, reported that it was “…as large as Jupiter and resembles a planet which is fading.”  This is a good description as Jupiter is typically about 45′ across, but much brighter of course! Another Frenchman, Charles Messier, independently found the same nebula later on in the same month while searching for comets. He entered into his famous catalogue as the 57th object (Note that the main reason for Messier’s famous list was so that he would remember these ‘fuzzy’ objects and not confuse them with Comets which were his main interest).

 

The following image was taken with my Celestron C11 telescope and an ATIK 383L cooled CCD camera. I used a filter called an H-Alpha filter which passes light in a very narrowband of frequencies. I was after the outer shell of M57 – something I had never really seen in older photographs, but nowadays it is commonly captured by amateur astronomers using sensitive CCDs. It does require long exposures to bring the faint outer shell out, and I stacked together several 20 minute exposures to reveal it here.

 

 

The previous, rather noisy, image is certainly not my finest moment! I really don’t have a good telescopic image of M57. So to finish this article with a splendid image, I asked Robert Gendler if I might use one of his (for those of you who don’t know, Robert is one of, if not the best deep-sky imagers and image processors in the world) . He kindly suggested that I use this incredible image of M57. For more information about this particular image, and about M57 in general see Robert’s page here:

http://www.robgendlerastropics.com/M57-HST-Subaru.html

 

That’s it for my take on M57. Maybe I’ll make the Zoom into theme a regular feature here, so watch this space!

 

 Posted by at 4:23 pm

Some recent deep sky images from home

 Deep Sky  Comments Off on Some recent deep sky images from home
Aug 072013
 

I haven’t blogged for a while, and I have some catching up to do! So, here are 3 images I took over the period April to June.

From June until early August in the South of England, the nights are very short and I don’t tend to be very productive in terms of deep-sky imaging, that’s one reason for using remote telescopes in other parts of the world. (but more about that in another blog).

All of these were taken using my trusty old Celestron C11 Schmidt-Cassegrain telescope with an AstroPhysics 0.67x reducer, giving an f-ratio of f/6.7. The CCD camera was an ATIK-383L mono with Baader 2″ filters. Guiding was achieved using a Starlight Xpress Off-Axis Guider unit (OAG). The whole lot rides on my AstroPhysics AP900 mount (which is currently out of action due to a dodgy Dec-axis encoder!).

The first one is Galaxy M63 (also known as NGC 5055, or the Sunflower Galaxy). This is a spiral galaxy in the constellation Canes Venatici consisting of a central disc surrounded by many short spiral arm segments. M63 is part of the M51 Group, a group of galaxies that also includes the more well-known M51 (the ‘Whirlpool Galaxy’).

 

Next we have the biggest and best Globular Cluster in the Northern Hemisphere. M13 is also known as the Great Globular Cluster in Hercules, and contains about 300,000 stars.

 

Finally, I’m very pleased with this image of the lovely face-on spiral galaxy M101. This galaxy, in Ursa Major is some 21 million light-years away, and is also known as the Pinwheel Galaxy.

 

 Posted by at 4:14 pm

The Eta Carina Nebula from down-under

 Deep Sky, Remote Imaging  Comments Off on The Eta Carina Nebula from down-under
Jun 102013
 

I’ve posted before about my exploits in using remote telescopes on the Light Buckets system from France, but I have recently been using the iTelescope network of telescopes which have observatories in New Mexico USA, Spain and also down-under in Siding Spring, Australia. The Australian setup, which is in New South Wales, is located at a latitude of about 31 degrees South, and allows access to those magnificent objects in the Southern sky that I have dreamed of imaging for a long time.

The Eta Carina Nebula is a huge, bright nebula that is roughly 4 times the angular size of the Orion nebula, but is imaged much less due to its southerly latitude (also, the Orion Nebula is perhaps the most imaged object in the night sky). The nebula is some 7500 light-years from Earth and hosts some of the most massive and luminous stars in our Galaxy, including the double-star system Eta Carinae, which weighs in at over 100 times the mass of our Sun.

The particular telescope I used has a very wide field of view and the full Moon would fit across this image nearly 8 times. To see the full-sized 3960 x 2612 image click here:  Full Size Image

 

So, what about the odd colours? Well, this is a narrowband image, meaning that I used 3 narrowband filters; In this case Ha, OIII and SII and combined them to make a false colour RGB image. Here’s a cropped version showing the central region at higher resolution (or see the full size image and pan around the whole thing)  Full Size Image

 Posted by at 9:38 am

Galaxy M106 and Companions

 Deep Sky  Comments Off on Galaxy M106 and Companions
Mar 052013
 

M106 is an interesting galaxy! Situated near the handle of ‘the plough’, in the constellation of Canes Venatici, it is roughly 22 million light-years away, and is known as a Seyfert  galaxy which means it has a very active nucleus. In fact, at the centre of M106 is a super-massive black hole. Now, our Milky Way galaxy has one of those too, as do most galaxies  but not as big as the one in M106. It is the material falling into the black hole that causes x-rays and other unusual emission lines to pour forth from this galaxy.

Besides M106, there are many other galaxies visible in this image. The lovely edge-on spiral  near the bright star at upper left is NGC 4217 and is thought to be a companion of M106. I have annotated a few of the brighter ones on the image, but there are many more if you look closely at the bigger sized image which is available here:

Click here for bigger image

As for the details of how this image was obtained. It was taken over some clear spells during 3 nights in late February and early March. A total of 27, 10-minute exposures were collected over this time through a white (luminance) filter, which is why this is a mono image. I will try and collect the R, G and B colours soon.  The telescope was my TS 130mm APO refractor at f/7 and the CCD camera used was my ATIK 383L.

 

 Posted by at 1:51 pm

A Starburst Cigar

 Deep Sky  Comments Off on A Starburst Cigar
Feb 242013
 

I have been using my trusty old C11 that I normally use for the Moon and planets to take some deep sky objects. The C11 gets used more this time of the year because it is ‘Galaxy Season’. This means that the Milky Way is not dominating the sky to us here at this time of the year as it is during the Summer months when it stretches across the sky, and that means that we can more easily see out of our galaxy to other distant galaxies without the plane of the Milky Way getting in the way.

This galaxy is often referred to a the Cigar Galaxy. It is Messier 82 and it is often shown together with M81, Bode’s Galaxy, but the field of view with the C11 and my ATIK 383L CCD will not fit them both in the FOV at the same time. This means we can zoom in on M82 which is only about 11 arc minutes across.

M82 is a bit of a strange galaxy to look at. It is a ‘starburst’ galaxy, seen edge-on and is also the closest starburst galaxy to the Milky Way. As a starburst galaxy M82 has a rate of star formation 10 times greater than our galaxy. Conditions for the starburst activity were believed triggered by a past close encounter with M81 between 300 and 600 million years ago which must caused gas and dust to be compressed into conditions favourable for star formation.

 Posted by at 1:51 pm

First Light Horse-Head

 Deep Sky  Comments Off on First Light Horse-Head
Jan 312013
 

I recently bought a new 130mm f/7 APO Refractor and have already posted one or two images from this new bit of kit. However, one of the reasons I wanted it was because it comes with a nice focal-reducer/field-flattener that brings the f-ratio down to about f/5. This gives a slightly wider field of view and is optically ‘faster’. In fact it is nearly twice as fast because the speed is related to the squares of the f-numbers being considered. So (7×7) / (5×5) = 49/25 = 1.96.

I’ve had the kit since November 2012, but, I was unable to achieve focus with the reducer in place! To cut a long story short, the reducer went back and it was discovered that the lenses had been assembled wrongly!

Anyway, here is my ‘First-light’ image of the Horse-Head Nebula in Orion. It is an H-alpha image (because the Moon was about) and consists of 11 exposures each of 20 minutes.

 

 Posted by at 4:55 pm

Cosmic Tadpoles

 Deep Sky  Comments Off on Cosmic Tadpoles
Jan 022013
 

A Happy New Year to all!

This is my first astro image of 2013, taken on New Years Day evening. It shows a nice emission nebula IC 410 in the constellation of Auriga. Maybe ’emission’ is an appropriate word here, as these two bright streamers in the stellar winds look like two sperm (or sperms – both seem to be correct) trying to enter an ovum!

 

This image is taken through a 130mm F/7 APO refractor, using a 7nm H-alpha filter. Recorded with an ATIK 383L CCD camera, this is the result of stacking 15, 20 minute exposures. Not as sharp as I had hoped – I think the seeing was a bit poor last night, as precise focusing was very difficult!

 Posted by at 1:53 pm