The Pleiades, M45 in Taurus is the closest Messier object in the sky and is easily visible to the naked eye. What is not visible is the beautiful nebulosity around the young, hot, blue stars that make up this open star cluster. However, long exposure astrophotography reveals the nebulosity and this image is an integration of 174, five minute exposures making a total exposure time of 14.5 hours. To see details of the telescope setup that I used to take this image from my home click here.
Click on the image below to see the full resolution version.
I captured about 23 hours of L, R,G and B data all in 5 minute sub-exposures and 28 hours of H-Alpha data in 20 minute subs. The H-Alpha really brings out the red nebulae in the spiral arms of this galaxy.
As usual, please click on the image to see the full-sized version.
This is the first image I have posted using data from my new remote telescope setup in Spain and it is, perhaps, the ‘deepest’ image I have ever processed. I have only recently taken over this system after I purchased it from First Light Optics who also kindly bequeathed me all their images taken over the last year or so that the system has been in operation. The images used to make up this image were taken over April and May 2021 when M81 and M82, both in Ursa Major, were higher in the sky. The larger galaxy on the left is M81 – Bode’s Galaxy and the smaller one is M82 – The Cigar Galaxy.
M81 and M82 were both discovered in 1774 by the German astronomer Johann Bode who reported his observation to Charles Messier who then added them to his famous catalogue. Both galaxies are about 12 million light years away (which is 114 million million km or 770,000 times further away than the Sun).
Here is the colour image; click on it to see a bigger version. More details follow the image below:
What else can we see in this image? Directly above M81 is a blue patch – you can see it better in the full sized image. This is a satellite galaxy to M81 called Holmberg IX. This is a dwarf, irregular galaxy and based on the observed age distribution of stars it contains it is thought to have formed within the last 200 million years, making it the youngest nearby galaxy known. This would explain the blue colour as the stars within it will be young and hot.
The faint wisps all around the galaxies are all part of the Integrated Flux Nebula (IFN), so-called because it shines by the total (integrated) light of all the stars in our Milky Way Galaxy. The IFN lies beyond the main body of our galaxy, and is illuminated by the whole thing. It is incredibly faint and only recently discovered in 1984 by the IRAS satellite. To show it better, I have stretched the histogram of the luminance channel of the above image even more. This monochrome image is shown below:
For those interested in the technical details of the image acquisition and processing, the image contains a total of 78.5 hours of exposures made up as follows:
112 x 5 minute exposures
112 x 5 minute exposures
98 x 5 minute exposures
287 x 5 minute exposures
83 x 20 minute exposures
The above table shows the actual number of exposures that were used in the integration to make the final image. Many more were rejected because of satellite or plane trails, or thin cloud etc (for example 73 of 360 L images were rejected). All images were calibrated with bias, dark and flat frames and all processing was performed in the amazing PixInsight software.
A few posts back, I showed a narrowband image of IC 1805 – The Heart Nebula taken during the full Moon. It looked rather pink as the H-Alpha signal is so dominant and overpowers any greens and blues that the OIII signal might provide. Here’s a new, differently processed, version (note: I’ve also flipped it so that the heart is the right way up!). Read below to find out what I did differently.
Using the amazing PixInsight software, I split the R, G and B channels apart. This meant that the resulting red channel contained just the H-alpha signal, but the green and blue channels shared the signal from the OIII emissions. I then made a new O channel by combining the green and blue channels using a formula of (2*G + B)/3 which gave a bias towards the better image I saw in the green.
Calling the red ‘H’ and the new combine green and blue ‘O’, I stretched their histograms, but also used a range mask on the O to stretch it much more (the mask prevented the background from becoming too noisy). This was the key to getting more blue in the resulting image. Then I recombined using HHOO to correspond to LRGB. Now you know why these are called false colour images!. However, all the data is real, it’s just a personal preference.
Here is my latest image from here in Ham, near Selsey. This is the beautiful Iris Nebula (NGC 7023) in the constellation of Cepheus. I took the images last night in a lovely clear, moonless sky from astronomical dusk to dawn. In all, 120 x 5 minute exposures were captured and I only had to throw away three of them because of very bright plane or satellite trails. This time, because there was no Moon, I was able to use the full bandwidth of a luminance filter on the QHY268C one-shot cooled colour camera.
The Iris nebula is an example of a Reflection Nebula. This is what Wiki has to say about these kind of objects:
In astronomy, reflection nebulae are clouds of interstellar dust which might reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible. Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars. Among the microscopic particles responsible for the scattering are carbon compounds (e. g. diamond dust) and compounds of other elements such as iron and nickel. The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized.
So, we can see that there could be diamonds in that dark dust!
Here’s the image. As always, click on it to see a much larger version in a new window.
The Great Orion Nebula (M42) and the nearby Horse Head Nebula (IC 432) are amongst the most photographed objects in the deep-sky. Of all the images I have taken of these beautiful nebulae, this is my favourite because it encompasses both of them in a single wide image, but still has enough resolution to show the intricate details and also the darker dust clouds in the Orion Molecular Cloud Complex.
Click on the image below to see a bigger version.
I took this image in January 2016 whilst Sue and I were renting a rural house in Southern Spain for the Winter months. The skies were lovely and dark at the house which was in the Cabo de Gata region of Andalusia.
More remarkably, I used a non-cooled DSLR camera in the form of my modified Canon 6D. Modified means that the filter that blocks the deep red part of the spectrum has been removed which makes the camera more sensitive to the Hydrogen Alpha emissions in these nebulae. Astronomers call this a filterectomy!
I took 60 x 4 minute exposures and then 30 or so shorter exposures of 30 and 15 seconds for the brighter core of M42. The shorter exposures where blended in to the rest of the longer, deeper exposures making this image and example of an High Dynamic Range (HDR) image. Without blending in the shorter exposures, the core would appear completely blown out and the finer structures would have been lost.
All processing was performed in PixInsight, including the initial calibration using bias, dark and flat frames.
This image of IC1805 – The Heart Nebula, in the constellation of Cassiopeia, shows what can be done when the Moon is very bright. Generally speaking, it is not easy to image faint deep-sky objects when the Moon is around, but it is possible to be productive by using narrowband filters. It’s not a great idea if the full Moon is also very close to the target, but as long as the Moon is 40 or more degrees away I find I can get reasonable results.
I explained a bit more about the dual-band narrowband filter I have been using with my one-shot colour CMOS camera in this post.
This image is composed of 48, 10 minute exposures over two nights last week. About two-thirds of them were during the night of the full Moon, the rest under an 85% Moon and drifting thin clouds.
As usual, click on the image to see the full-sized version.
The Heart Nebula is an emission nebula about 7,500 light years away. The great astronomer William Herschel discovered this nebula in 1787. Glowing in the light of ionised Hydrogen gas, the signal is strong in the H-Alpha part of the spectrum. The OIII signal is much weaker and since the H-Alpha is mapped to the red channel, the colour is predominately red.
There is a cluster of stars at the centre known as Mellotte 15 and this is shown as a crop from the main image below.
I’m very excited about this! I have finally taken the plunge and now have (or will have in early November) a remote imaging rig in Southern Spain. It is located at the PixelSkies remote hosting facility near Castilléjar in the province of Granada, Andalucia.
The imaging rig itself was originally built in 2020 and owned by First Light Optics, and it was used to capture images for a monthly image processing competition. I learned from Ian King that it was for sale and I couldn’t resist the opportunity to buy this, already proven, setup. Normally, one has to buy the kit and ship it out to the hosting location, all of which takes time, planning and money.
Here’s a picture of the whole system located in one of the roll-off roof sheds. More details and pictures are below.
The telescope itself is a StellaMira 104mm ED2 Triplet f/6.25 APO Refractor (with field flattener) and this rides on an amazing 10Micron GM 1000 HPS mount which has absolute encoders. The detector is a Starlight XPress TRIUS PRO 694 mono CCD camera which has 2750×2200 pixels in a medium format Sony chip. The resulting field of view is 66 x 53 arcminutes at a resolution of 1.44 arcseconds per pixel. To give an idea of what this means, the Moon would fit twice across the resulting images. The picture below shows the CCD camera connected to the telescope.
Also visible in the picture above is the 7-position filter wheel containing Optolong 1.25″ filters. The filters are the usual set of LRGB filters and the three 7nm narrowband filters for HA, OIII and SII. Notice also the Off-Axis Guider (OAG) with the Starlight Xpress LoadStar V2 guide camera siticking out to the right of the filter wheel. The pick-off prism for the OAG is in front of the filters so that unfiltered light always hits the CCD sensor of the LoadStar.
The picture below shows the 10Micron mount more clearly and also the Lakeside Astro motorised focuser. It is, of course, vital to be able to accurately focus remotely and the focus point will vary with temperature during the night, and is also different for each filter.
Also shown above is the mounting plate on top of the telescope cradles which has the red Hitec Astro Mount Hub Pro V4 control box. This has a full USB hub along with software controllable power ports and dew heater controller. This hub allows the cabling to be kept shorter and neater. Without a control hub like this, all the cabling would have to travel down to the PC on the floor and would create potential cable snagging issues as the telescope slews around. Here is a close up of the hub:
Another fantastic feature of this setup is the built-on flat panel. This Alnitak Flip-Flat will allow me to take my own flat-field images without asking anyone to arrange for a flat panel to be balanced on the telescope. This device can be seen at the front end of the telescope and it also acts as a lid for the telescope to prevent dust getting on to the objective lens. The opening and closing of the panel is software controlled as is the brightness of the flat panel. During cloudy nights I can also take bias and dark frames when the panel is in the closed position, but turned off. See the picture below which also shows the wide angle video camera (the red device below the flip-flat). This sensitive camera provides a wide view of the sky, useful for spotting clouds or generally admiring the constellations and the Milky Way.
Mounted on the mount pillar is a small Astromi.ch MBox device. This is a small, self-contained weather sensing device that delivers barometric pressure, temperature, humidity and dew point information with high accuracy. There are other bits and pieces (including the main Windows 10 control PC), but I have described the main components.
In due course I’ll share more information about how I get on with this fantastic system, and hopefully, lots of great images from this dark-sky site.
Finally, watch this video to see the system being assembled a year or so ago.
Following on from my last post with the Andromeda Galaxy, here is another beautiful galaxy which is also part of a group of galaxies known as the Local Group. The Andromeda Galaxy and our own Milky Way are the two largest in the group and this one known as the Triangulum Galaxy is third.
Why the Triangulum Galaxy? This is simply because it can be found in the small constellation of Triangulum – the Triangle! Just about any group of three stars might do, but this particular triangle is found above Aries and below Andromeda.
Again, as with my M31 image, the Optolong L-Extreme filter was used to collect the H-Alpha data which was then blended into the red channel. This enhances the pinky-red regions on nebulosity in the spiral arms of the galaxy.
As usual, click on the image below to see the full-size version.
For the technically-minded, this article shows the equipment used to take this image.
I acquired the images using N.I.N.A. software. I took 72 x 300s exposures with the QHY268C camera for the RGB and 17 x 600s exposures using the L-Extreme dual-narrowband filter to get the Ha data which I combined with the red channel from the RGB. All processing with PixInsight.
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…