M31 – The Andromeda Galaxy

 Deep Sky, Equipment, General Astronomy, Image Processing  Comments Off on M31 – The Andromeda Galaxy
Oct 132021
 

Messier 31, the great galaxy in the constellation of Andromeda is one of the most photographed night-sky objects of all, probably second only to the Orion Nebula. Every few years I get an itch to image it again. Most astro-photographers like to revisit old targets once in a while, and this often happens when new telescopes and cameras have been purchased, and this is the reason why I’m having another go at this beautiful object. I showed off my new kit in my previous post.

It is often said of M31 that it is the furthest away object that can be seen with the naked eye. This is an amazing thing when you think about it! This galaxy is about 2.5 million light years away and it is the nearest large galaxy to our own Milky Way galaxy which is not too different in structure from M31 itself. In a dark, moonless sky, M31 looks like a fuzzy blob to the naked eye. Some people say they can also detect another nearby galaxy called M33 – The Triangulum Galaxy with the naked eye. I personally can’t see M33, but it is further away from us than M31 at around 2.75 million light years, so M33 really does represent the furthest thing anyone can see without optical aid of any kind. I’ve asked a lot of people if they can see M33 in a good, dark sky in the UK, but I’ve never found anyone who can, so I’m happy that those photons that left the Andromeda Galaxy when Homo habilis first walked the Earth, enter my eye and are detected by my retina represent the most ancient particles of light that can ever stimulate the human consciousness.

Here is my latest image of M31. Click on the image below to view a much larger version (4000 pixels across). Next, I will describe some more details of how this image was acquired and processed.

Firstly, what are we looking at here? The first thing to realise is that we are viewing this spiral galaxy from an angle of about 45 degrees. If we could fly over the galaxy and look directly down on it, we would see a vast spiral shape. Another thing to understand is that all of the distinct, bright stars in the image are all relatively close-by stars in our own Milky Way – in other words we are looking through a ‘curtain’ of nearby stars to see outside our own galaxy. We should understand that galaxies are vast islands of stars, separated by huge distances of near-empty space. The Andromeda Galaxy contains about a trillion stars (that’s a million, million stars) which is about twice the number in our own Milky Way galaxy. So, you are looking at all of these trillion stars in this image which are too far away to see them individually, so they glow like a huge mass.

What else can we see here? Well, you will see the dark regions in the galaxy. These are huge lanes of cosmic dust which are obscuring the light from stars behind them. Also, if you zoom in to the big image you will see the disk of red regions that glow around the galaxy. Here’s a zoomed in region that shows the red regions nicely. Each of these red areas shines be the light of Hydrogen-Alpha. All of them would be seen as nebulae to any inhabitants of planets orbiting the stars in M31 and any of them could be the equivalent of, say, the Orion Nebula that we see locally here in our region of the Milky Way.

Lastly, there is a bright elliptical blob showing below M31 in the main image. This is a dwarf elliptical galaxy called M110 which is a satellite to M31 itself. We have similar objects associated with the Milky way and they are known as the large and small Magellanic Clouds.

So, how did I create this image? I used the telescope and camera system I showed in my previous post. Over four clear nights in October 2021, I took lots of long exposure photographs of M31. The telescope was guided very accurately by the separate guide scope that was checking the guiding accuracy every 2 seconds throughout the whole time, and instructed the mount to make tiny corrections to keep the galaxy perfectly still on the chip of the sensitive camera. Eventually I had about 22 hours of exposures stored on my imaging computer. By the time I weeded out the poorer frames, I had 10 hours of data from my broadband luminance filter, and about 7 hours of data from my narrowband filter.

The narrowband filter I used was the 2″ Optolong L-Extreme filter. This passes light from both H-Alpha and Oxygen-III sources, both with a passband of 7nm wide. In this image I only wanted the H-Alpha data, so I extracted the red channel from the narrowband images and threw away the green and blue which shared the OIII signal. Then I merged the H-Alpha signal with the red channel from the broadband RGB images. This enhanced the red emission nebulae in M31 beautifully.

I’ll write a more detailed blog about my process next…

 Posted by at 2:13 pm

My new deep-sky imaging setup

 Deep Sky, Equipment, General Astronomy  Comments Off on My new deep-sky imaging setup
Sep 292021
 

Since the early Summer of 2021 I have been building up a new deep-sky imaging setup based around the beautiful and venerable Takahashi FSQ-85EDX Refracting telescope. I’ve always wanted a ‘Tak’ and decided to go for this model known ad the ‘Baby-Q’. The optics are glorious and the focuser is incredibly rugged and can carry heavy cameras and filter wheels.

The idea, eventually, is to turn this setup into a fully robotic system which will be mounted low to the ground and housed in a simple box-like structure with a sliding roof. For now, I’m testing out the system to see how it performs.

Here is a small gallery of photos of the current system. I will add more details about the components below.

Here’s a list of the main components that you can see in the above photos:

  • Telescope: Takahashi FSQ-85EDX F/5.3 Apochromatic Refractor with 1.01x field flattener.
  • Mount: Skywatcher AZ-EQ6 Pro
  • Camera: QHY268C cooled CMOS camera (one-shot colour, full 16-bit)
  • Filter Wheel: Starlight Xpress 5 x 2″ filter wheel
  • Guide Scope: ZWO 60mm. Focal length is 280mm, F/4.67
  • Guide Camera: ZWO ASI290MM Mini mono
  • Auto Focuser: Pegasus Astro FocusCube2
  • Power, Dew Heater and USB Hub: Pegasus Ultimate Powerbox V2
  • Dew Heater bands on both scopes
  • Windows Computer: Beelink Mini PC (in the plastic box on the ground running N.I.N.A.)

If you look at the photos with all the cabling, you will see a plastic box on the ground below the mount. This contains a ‘headless’ mini PC running Windows 10. Think of an Intel NUC and you will get the idea, but this is a Beelink with an Intel i5 CPU which comes cheaper than a NUC. This computer has all of the software installed to control the rig. I’m using the free N.I.N.A. software here and the little PC is connected to the wireless router I have in my dome just a few feet away. This allows me to use remote desktop from the comfort of my dome, office or house.

The thing that really was a ‘game-changer’ for me is the Pegasus Powerbox which is mounted just below the lens of the main scope. This provides all of the 12-volt power ports I need to run the various bits of kit and also has a USB hub with 6 ports. Additionally it can power and control the heat of three heater bands and can detect the dew-point so that it can intelligently adjust the power to the bands to keep the lenses free from dew. Because nearly everything connects to this hub, there are only two cables that need to be connected to the big plastic box on the ground. One is the 12V power to the hub and the other is the USB3 port to the Beelink mini PC.

I run the amazing free N.I.N.A (Nightime Imaging ‘N’ Astronomy) software on the mini PC and the recently added Advanced Scheduler is amazing allowing me to power up the system before dark and set up various targets to image during the night. The system will do everything such as cooling the camera, auto-focusing, slewing and centring targets, flipping across the meridian and shutting down at dawn. It can also deal with re-focusing during the night if the focus drifts and re-centring after a cloudy spell.

Assuming I get some clear nights over the Autumn months, I will hopefully be posting some new images soon.

 Posted by at 3:21 pm

The Veil Nebula – a mosaic

 Deep Sky, General Astronomy, Image Processing  Comments Off on The Veil Nebula – a mosaic
Sep 292021
 

The beautiful Veil Nebula in the constellation of Cygnus (the Swan) covers a large apparent area of the sky. When I say ‘large’ I mean it in a relative way. It covers a large enough area to make it hard for the average telescope to cover in one frame. To put this into perspective, the full Moon (or the Sun) is about half a degree across, but we need a field of view (FOV) of about 3 by 3 degrees to encompass the whole of the Veil Nebula. Thus, we can say that the full Moon would fit about 6 times across the apparent span of the Veil Nebula.

I have a lot of different telescopes and cameras! Some telescopes, such as the popular Schmidt Cassegrain design, are good for viewing the planets and small galaxies, but these typically have very small FOVs because they have long focal lengths to provide the high magnification which we need to see the belts on Jupiter, the craters on the Moon, or the rings of Saturn. Think of these telescopes as the telephoto lenses of the astronomer’s toolkit. Then there are the shorter focal length, smaller telescopes. These are the type (typically small refractors) that can give a wider view of the starry sky and they are ideal for delivering a larger FOV on to the camera’s sensor. However, only the smallest of these could cover the 3 by 3 degrees we require, and so I have resorted to the technique of imaging one half of the Veil Nebula on one night, followed by the other half on another night! I used an using an 85mm F/5.3 refractor. The two sets of images are ultimately processed and seamlessly joined together in a mosaic to show the Veil Nebula in one final image. Although this sounds complicated, there are advantages to this approach as the final image provides a much higher resolution of the target than could been obtained with a telescope that could fit the whole thing in in one go. The final image ends up with more pixels too.

The Veil Nebula is a Supernova remnant. The star that blew itself to pieces was 20 times more massive than the Sun and was just over 2,000 light years away. This cataclysmic event happened about 10,000 years ago. The remaining remnant structure is about 110 light years across and contains the beautiful glowing filaments that you can see in the image. The red colour is caused by ionised Hydrogen atoms, and the green from doubly ionised Oxygen atoms. The filter that I used to capture this image allows light of these two colours (wavelengths) to pass through, but cuts off everything else, including general light pollution and moonlight etc. Astronomers call this narrowband imaging.

Click on the image below to see a full-sized version.

 Posted by at 9:48 am

Three new images from the summer

 Deep Sky, General Astronomy, Image Processing  Comments Off on Three new images from the summer
Sep 282021
 

Here, on the south coast of England, the nights get very short indeed for a couple of months around the Summer Solstice. In fact, there are several weeks where theoretical ‘astronomical twilight’ never ends and the Sun never drops below 18 degrees below the horizon. I normally abandon deep-sky imaging but, this year, I was testing out a new system and decided to have a go at a few easy and classic Summer deep-sky targets.

The main thing that helped my productivity during these short nights was a new dual-band narrowband filter from Optolong called the L-Extreme. These multi-band filters are becoming very popular with deep-sky imagers these days. The pass-band spectrum graph is shown below, and you can see that there are two peaks – one centred on H-Alpha and the other on OIII and both are 7nm wide.

I’ve been imaging with Ha, OIII and SII narrowband filters for many years, but so often in the past I have been unable to capture a full set of sub images due to poor weather or lack of time, and this filter brings the possibility of acquiring more finished images as these three testify. By the way, the SII band is not included with this filter but, so often, the SII signal is so weak it rarely adds much to an image. However, since I have this filter in my filter wheel (so that I can use a Luminance filter for RGB imaging) I still have the option of adding my SII filter into the mix if I so desire.

I should mention that these narrowband filters are generally used with one-shot colour cameras. The Ha signal ends up in the red channel and the OIII signal is often mixed between green and blue. My new system includes the amazing QHY268C one-shot colour cooled CMOS camera which is very sensitive and has 16-bit resolution.

I will add a separate article showing the new setup, but it includes the superb Takahashi FSQ-85EDX APO refractor working at f/5.4 riding on a Skywatcher AZ-EQ6 Pro mount. The field of view is 179′ x 120′ which is 3 x 2 degrees (1.72 arc-seconds per pixel).

All three images consist of just over 2 hours of exposures – that’s all the darkness I had on each night! I took 600 second exposures throughout and calibrated with dark, flat and flat-dark frames.

Please click on each image below to see the full size of the images (which are only 50% of the originals).

The first image is the North America Nebula in Cygnus (NGC7000)

The second is IC1396 in Cepheus which contains the Elephant Trunk Nebula near the middle.

Lastly, NGC6888, The Crescent Nebula in Cygnus which is sometime referred to a van Gogh’s Ear!

Hopefully, my next article will not be too long coming. Thanks for reading.

 Posted by at 11:00 am
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