The Virgo Cluster consists of more than 2,000 galaxies, which unfortunately are optically too much for my small William Optics GT81 telescope individually. However, one of several sub-groups within the Virgo Cluster forms a striking J-curve shape that does make for a pleasing LRGB image. Discovered and named after the Armenian astrophysicist Benjamin Markarian, Markarian’s Chain is a string of bright galaxies that share a common motion through space. I first imaged the Chain in April 2015 using a modded DSLR and then again in April 2017, as my first LRGB image with the then new ZWO ASI1600MM-Cool camera but with integration times of less than 1-hour on both occasions, the resulting images were far from ideal. On this occasion using my new Chroma LRGB filters for the first time I was determined to do better.
The new filters and nearly 7-hours integration time has resulted in a much more dynamic and detailed image, which I believe now does justice to this spectacular group of galaxies. Analysis of the image using Astrometry.netshows just how crowded this area of Virgo is with galaxies (see annotated image above) but it is Markarian’s Chain that inevitably stands out together with a few other adjacent galaxies.
Large 10th magnitude M84 & M86 galaxies at the western end of the Chain dominate the image. M84 is the object with the highest blue shift in the Messier catalogue, which is a result of its rapid movement (244km/sec) towards the centre of the Virgo Cluster and us. At the centre of M84 is a 1.5 billion solar mass black hole.
NGC 4420 & NGC 4388 – by comparison these edge-on galaxies together with even smaller NGC 4413 & NGC 4425 seem to frame the larger M84 and M86.
Next along the Chain is a pair of interacting galaxies, the smaller round shaped NGC 4435 and NGC 4438 with its distorted disk, known as “The Eyes”.
As the Chain starts to turn, some 20’ along is NGC 4458 and its partner, the 11th magnitude elliptical NGC 4461.
The final section of the Chain consists first of NGC 4473, its brightness generated by a supermassive black hole – at 100 million solar masses its diameter of 4.46au which would stretch from the Sun to the asteroid belt! Thereafter the 11.4 magnitude barred lenticular galaxy NGC 4477 defines the north eastern extremity of Markarian’s Chain.
As previously noted, there are many other galaxies in this part of the Virgo Cluster. Perhaps most notable though is M87, from which the first ever image of a black hole was the obtained in 2019 – consisting of some 6.5 billion solar masses.
All-in-all Markarian’s Chain makes for a rewarding image using my small telescope combined with the new Chroma filters. Such is the nature of the image the galaxies might also suggest a string of pearls or perhaps galactic stepping stones – metaphorically leading to the next phase of my astroimaging journey.
IMAGING DETAILS
Object
Markarian’s Chain
Constellation
Virgo & Coma Berenices
Distance
50 – 55 million light-years
Size
~2.5o total
Apparent Magnitude
Varies +10 to +12 approx.
Scope
William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera
ZWO1600MM-Cool mono CMOS sensor
FOV 2.65o x 2.0o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
The history of astrophotography will record a period of rapid innovation during the past decade, amongst which one of the stand-out developments has been that of the CMOS sensor based camera, notably the ZWO ASI1600MM-Cool (see below). Just look at any astrophotography website such as Astrobin and it won’t take long to find an image taken with this camera such is its popularity. It is this very camera that I was fortunate to purchase in December 2016 shortly after its release and has been the core of my astrophotography set-up ever since.
I have generally been very happy with the results achieved with the ZWO camera, although an issue sometimes occurs when imaging large stars, so called ‘star bloating’. There are a number of theories discussed ad nauseam online why this might occur, of which microlensing and / or diffraction seems most likely and probably relates to either – the sensor, sensor cover or filters. Since beginning with the ZWO camera I’ve used their excellent matching EFW with LRGB and 7nm narrowband filters. Notwithstanding, the filters are considered to be somewhat ‘low end’ by the aficionados of such things and after living with the ZWO filters for some time, at considerable cost I recently decided to upgrade to a set of Chroma 31mm filters – LRGB + 3nm narrowband. Together with Astrodon, Chroma filters are generally considered to be the best and my expectations were therefore high.
Being unmounted I’d previously found the ZWO filters tricky to install using the small screws and fibre washers supplied. At 3mm Chroma are physically 1mm thicker than ZWO filters and also need to be fitted in a specific direction, which is ‘letters up’ or with top of the ID letters on the side of the filter facing towards the sensor; this is disputed by the manufacturer but there’s substantial first-hand experience online that suggests otherwise. With these issues in mind I sought out bespoke filter masks and longer M2 6mm screws to hold the thicker filters firmly in place. The 3D printed masks from Buckeyestargazer in the USA did a great job securing the filters and are better than those from ZWO – the internal edge of the mask forms an L-shaped ledge into which the filter fits snuggly. Ready to go, I then had to wait nearly 4-months before the clouds parted to try out these expensive pieces of glass and then it was a full moon – I often wonder if astrophotography is a good hobby to choose in the United Kingdom but it’s too late now?
Chroma filters secured with Buckeyestargazer masks and ready to go
Given the presence of the moon it therefore had to be suitable narrowband target and after three years since I’d last imaged this object it was an opportunity to have another go at NGC 2244 AKA the Rosette Nebula, though being late February there was limited time each night before the object sunk low behind trees on the western horizon; coincidentally the ZWO ASI1600MM-Cool First Light in early 2017 was also the Rosette. Before starting serious imaging I first tried some test shots to make sure everything worked OK and immediately discovered that the change from 7nm to 3nm had a significant impact on light gathering, thus requiring greater exposure times of an unprecedented 10 minutes. Not surprisingly this was also apparent when taking flats which increased exposure time of up to x10 longer in duration compared to the ZWO filters; conversely preliminary but limited tests on the broadband filters seem to indicate greater transparency and thus shorter exposures, time will tell if this is correct.
So was it all worth it? I’m very pleased with the final image which was processed using the SHO Hubble Palette with PixInsight and Photoshop (see top of the page). There are a number of significant bright stars in and around the Rosette which the Chroma filters have handled well but overall it is the more delicate tone that has been achieved which is most pleasing. Fundamentally the 3nm filters have produced a more subtle quality to the overall image and in particular the nebulosity. In addition, applying Hartmut Bornemann’s excellent colour calibration script AutoColor for the first time (see Visible Dark’s video tutorial here) has resulted in a soft but exciting colour palette.
Subsequently I have focussed on the inner region of the nebula which contains the so-called ‘Carnival of Animals’ (see above), which has been cropped and reprocessed individually to show-off the ‘animals’ or Bok globules – named after the Dutch-American astronomer Bart Bok, who in 1947 proposed that these dark nebula indicated clouds of dust undergoing gravitational collapse as part of the process of new star formation, which has since been confirmed. In conclusion I’d therefore say that despite the obstacles, issues and long wait, on the evidence so far the addition of the Chroma filters to my set-up has been very successful – transformative in fact. Now I wonder if they make something that removes the clouds?
IMAGING DETAILS
Object
NGC 2244 + 2337 + 2238 + 2239 + 2246 AKA the Rosette Nebula
Constellation
Monoceros
Distance
5,200 light-years
Size
65 light-years
Apparent Magnitude
9
Scope
William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera
ZWO1600MM-Cool mono CMOS sensor
FOV 2.65o x 2.0o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
In ancient history Orion’s stars were considered to form a pattern that resembled a hunter holding a club above with his right arm and a shield in front with his left. The appearance of Orion each year marks the highlight of the astronomy for many including me but for the second year running months of continuous cloud have precluded any astronomy since October; I note from comments online far-and-wide that this phenomenon has prevailed across much of the northern hemisphere, no doubt resulting in a lot of unhappy astronomers.
The Anantomy of Orion
Finally the clouds briefly relented over Fairvale Observatory in February but only for a few hours each time, thus eliminating the possibility of imaging with a CMOS mono camera. Faced with these problems I therefore returned to my somewhat neglected modded Canon 550D camera and suitable lenses for appropriate widefield compositions, in order to image some classic targets around the Orion constellation in a broader context. Having first whetted my appetite with the Samyang 135 f2 and its large 9.45o x 6.30o FOV to successfully image the iconic area that encompasses Orion’s belt, the Horsehead Nebula and M42 (see Going Big), it was time to go really big in order to capture the entire constellation literally and figuratively in a new light.
Seven bright stars define the area which outlines the torso and upper legs of Orion the Hunter: Betelgeuse, Bellatrix, Rigel and Saiph at the top and bottom, connected across the centre by his ‘belt’ formed from Alnitak, Alnilam and Mintaka. The H-shape thus created by these stars is a familiar sight over the winter months but like so many asterisms of the night sky all is not what it seems. Plotting the distance from Earth of each star it is immediately obvious that their spatial relationship significantly changes the shape of the constellation compared to what as we perceive by eye. It is a sobering thought that with the passage of time those asterisms familiar to astronomers today will look very different in the future as the stars move though space and therefore continue to change their relative positions, look and shape.
Star
Betelgeuse
Bellatrix
Rigel
Saiph
Alnitak
Alnilam
Mintaka
Distance from Earth*(light years)
643
243
772
724
800
1,359
900
*Source: Royal Greenwich Observatory
Click HERE for annotated version of the Orion Constellation in 3D ref. Space Science Telescope Instititue
The Canon ‘Nifty Fifty’ 50mm f1.8 fixed aperture lens is perfect for an ultra widefield image of Orion. Whilst the glass is excellent, focus leaves a lot to be desired and once achieved needs to be secured with tape
Aside from the said visual perspective of Orion, like so much of space we only see a fraction of what is really present in the Universe but can nevertheless often be disclosed by astrophotography. And so I next decided to image the entirety of Orion, this time with a basic Canon 1.8 50mm lens – the so called “nifty fifty”- with the purpose of capturing in one shot the constellation with which we are all familiar, together with vast spectacular HII-regions that encompass much of the constellation but usually remain unseen. This camera-lens combination provides an enormous 25.5o x 17.0o field-of-view (x7 > Samyang lens, x83 William Optics GT81!) albeit with lower resolution, which perfectly encompasses most of Orion and therefore the entire arc of Barnard’s Loop on the left and the Angelfish Nebula (Orion’s “head”) located above and between Betelgeuse and Bellatrix.
Above:Orion constellation from Fairvale Observatory 24th December 2014 (Left) compared with long exposure image + modded camera 10th February 2020 (right)
Barnard’s Loop is an emission nebula, forming part of the Orion Molecular Cloud Complex which also contains the dark Horsehead and bright Great Orion Nebulae M42. The Loop is believed to have originated from a supernova explosion about 2 million years ago, which is now ionized by stars from within and around the Orion Nebula and takes the form of a large arc centred approximately on the Orion Nebula. Discovered and photographed by E. E. Barnard in 1894, this vast feature extends over some about 600 arcminutes when viewed from Earth or physically up to 300 light years across, depending on the distance from Earth.
The Angelfish Nebula SH2-264 is centred on the young star cluster of Lamda Orionis, of which Meissa is the brightest. An HII-region with an apparent size of 5 degrees and actual size of 150 light years, it is also an emission nebula that is energised by the aforesaid star cluster and is considered to form the so-called head of Orion.
Having previously imaged notable parts throughout Orion, I’ve long wanted to capture the full extent of this wonderful constellation in all its glory and am very pleased with the outcome on this occasion.
DSLR IMAGING DETAILS*
Object
Orion Constellation
Constellation
Orion
Distance
243 to 1,360 light-years
Size
594o2
Apparent Magnitude
Varies
Lens / Scope
Canon 50mm f1.8
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
No Guiding
Camera
Canon 550D modified
FOV 25.5o x 17.7o Resolution 17.72”/ pixel
Capture & Processing
Astro Photography Tool + PHD2 Deep Sky Stacker, PixInsight, Photoshop CS3 & Topaz Denoise AI
Image Location & Orientation
Centre RA 05:37:37.3 DEC +00:48:50.26 Top = North Right = West
Exposures & Aperture
42 x 120 sec @ ISO800 Total: 1hr 24 min F1.8
Calibration
5 x 120’ Darks, 20 x 1/4000 sec Bias 20 x Flats
Location & Darkness
Fairvale Observatory – Redhill – Surrey – UK Typically Bortle 5-6
Date & Time
10th February 2021 @ +21.00h
Weather
Approx. <=0oC RH <=65% 🌙 NEW MOON
*For higher resolution and plate-solving data go to AstrobinHEREand click on image
After starting astronomy in 2014, Watch This Space (Man) was launched shortly thereafter as a personal record of my then nascent astronomy journey. Apart from the main blog about my progress or otherwise, links to other astrophotographers, astronomy tools, astronomy weather, scientific papers etc. can also be found on this website; I was suprised to see that to-date 152 items have been published on this site.
I always like to hear from others – comments, questions, help or just to say hello – and can be contacted via: graham.s.roberts@gmail.com or just leave a comment at the end of any item if you prefer.
Vistor map 2020: In this most difficult of years for everyone, it’s especially heartening to see so much interest from all corner’s of the world and hope to see you and others again in 2021 – Clear Skies!
REFLECTIONS is a review of my astronomy and astrophotography during the past year, together with some thoughts on possible future developments.
2020 Overview, Images & Goals for 2021
For the world 2020 was a year like no other. Notwithstanding the obvious problems and dire consequences of Covid-19 for everyone, there have been surprising benefits for astronomy. Although I am retired, under lockdown there was even more time available for hobbies. Furthermore, as I live close to Gatwick and Heathrow airports + underneath numerous high altitude long-haul overflight paths, a massive reduction in air travel resulted in a very obvious improvement in seeing conditions, which was confirmed by guiding results. Located in a Bortle 5 to 6 area I ordinarily achieve at best average RMS error guiding of 0.90” to 1.50”/pixel, guiding improved markedly during lockdown to between 0.50” to 0.75”/ pixel. Of course such seeing conditions also resulted in better quality imaging itself and on a number of occasions I was able to achieve integration times of 10-hours or much more over a number of nights. The result was better images but less of them and inevitably, a lot more cloud throughout the rest of the year!
Having previously got to grips with plate solving, using the new CdC planning function I intended to develop the use of mosaics this year. However, such is the weather in the UK (see above) that it’s obvious to me that creating mosaics is probably not the best use of what imaging time we get. Undeterred, during January I planned and shot a 15x panel mosaic of Barnard’s Loop in Ha-wavelength. Unfortunately the unpredictable occurrence of patchy cloud invalidated some of the panels, though I was finally able to compile a 7x panel mosaic of the upper easterly section of Barnard’s Loop – see below. Notwithstanding, there were lessons learned: (i) restrict mosaics to one or two panels and / or (ii) where wider view images are required use a wide FOV set-up rather than a large mosaic.
Most of my other objectives for 2020 turned out to be pipedreams e.g. a new observatory or perhaps a larger telescope or dual rig. Despite this there were important developments on other fronts.
After eventually coming to the conclusion that mosaics were probably an unwise way to go considering UK conditions, it became clear that a suitable high-quality camera lens might produce similar coverage with less imaging time and hassle. Thus also inspired by the images of others on the SGL Forum using such equipment, I set out to build a new rig based around the excellent Samyang 135 f2 lens. This project remains work-in-progress but so far using the lens with a bespoke 3D printed rig and micro focuser made by Astrokraken and a modded DSLR, it’s apparent that this lens produces excellent widefield images in a relatively short time.
Initial Samyang 135 f2 set-up with modded DSLR
With the time and ‘opportunity’ afforded by lockdown throughout most of the year, I finally decided to do something about improving my processing, namely learning PixInsight. Unfortunately the rumours were correct – it is a steep learning curve and altogether a less than user friendly software. However, after many weeks of toil and expletives I’m pleased to say I can now process an entire image with PixInsight, the impact of which has been nothing less than profound. However, whilst PixInsight is an excellent processing facility, I’ve come to the conclusion that it is often best used together with other process software where appropriate for specific tasks:
Deep Sky Stacker for calibration, alignment and stacking; the equivalent PixInsight process is just too complicated and time consuming;
Photoshop can be very helpful finessing colours and stretching (Levels & Curves);
Starnet++ is useful for creating starless images, which then help to get the best from processing nebula separately before re-combining with the stars;
Topaz AI Denoise has been very effective and easy to use for noise reduction and sharpening at any point during the workflow.
This combination for processing has turned out to be something of a game changer and almost certainly was the most important astrophotography development of the year for me, which augurs well for 2021 and beyond.
Favourite Images
Continuing with the theme of less is more, I imaged just 13 objects this year – of which three were experimental & three with a DSLR – but still with a total integration time of 80 hours (2019 17 objects & 65 hours, 2018: 25 objects & 43 hours). Having worked through many of the astronomer’s favourites by now, images in 2020 consisted of: a new approach to old favourites, difficult / small objects for my equipment e.g. galaxies or less popular and widefield targets.
I’m pleased to say that most of these images turned out well and it’s difficult to choose a favourite. The so-called ‘favourites’ below therefore represent those images from this year that portray an important development in my astrophotography journey. More detailed reviews of these and all other images from 2020 can be found in specific articles that can be accessed using the links found below or via the Blog Index, located under the dropdown menu ABOUT.
Heart Nebula: Although imaged in 2018, this version has been re-processed using mainly PixInsight, thus transforming the original SHO Hubble Palette image from something rather dull to one with warm, vibrant colours, as well as much great detail – demonstrating the significant impact of my new PixInsight based processing abilities.
LBN 325: Numerous emission nebulae populate this small part of a very extensiveHII-Region, which forms an exciting LRGB image. Processing was complex and difficult, in order to bring out exciting features that abound in this spectacular but less popular area of the Cygnus constellation. Integration time of 10-hours was obtained over three nights and is my first LRGB image processed using PixInsight.
M63 Sunflower Galaxy: At 12.6’ x 7.2’and apparent magnitude of +9.3,this small flocculent galaxy in the Canes Venatici constellation is a challenge for my equipment. However, with 8 hours 20 minutes exposure over three nights in April and careful processing, the all-important detail within the galactic disc is clear. Topaz Denoise AI and Gigapixel software played an important role in maintaining the colour and delicate detail in this +50% cropped image.
Taken from last year’s REFLECTIONS 2019:
“Although you never know, I don’t see any major breakthroughs in the coming year”. Just goes to show what I know, fewer but better images were obtained in 2020:
RECORD CARD 2020
Goal
Specifics / Results
Outcome
Improve image capture
Further Improvements in overall quality + much longer integration times + better guiding accuracy = less but better images.
MUCH BETTER
Better processing
Using PixInsight software combined with Photoshop, Starnet++ and Topaz Denoise AI has led to major processing improvements and much better final images.
MUCH MUCH BETTER
Widefield Imaging
Initial results from new imaging rig based around Samyang 135 f2 lens were very promising but there’s more to do.
BETTER
My main objectives for 2020 were largely fulfilled (see above), so what about 2021?
Imaging: Other than maintaining the aforesaid improvements achieved over the past two years – guiding & longer integration times – two items that still need to be addressed are: (i) upgrade filters to remove star bloating and all round better images, (ii) improved focussing.
Widefield: Complete Samyang-rig build and switch from DSLR to CMOS mono camera.
Consolidate processing improvements: Whilst the move to PixInsight and other software was very successful in 2020, I’m still only scratching the surface of what’s possible.
Upgrade mono camera – there’s a new generation of colour CMOS cameras starting to appear, hopefully soon to be followed by their mono equivalents !
Hardly a year I and the rest of the world will want to remember, though more than ever astrophotography played a big role in providing relief from the trauma going on around us all.
The major increase of integration times achieved and the use of PixInsight has proved transformative for my astrophotography and will justify returning to reimage some old favourites in future years. I had often thought about upgrading my OTA to something bigger but given the lack of a permanent observatory here at Fairvale Observatory, combined with long periods of bad / cloudy weather, the penny finally dropped and I now have high hopes for the little wonder that is the Samyang 135 f2 lens when I complete its set-up in 2021.
Looking back I have to be happy with my astrophotography in 2020 but more importantly, look forwards to an even better year which holds great promise building on the positive developments of the past 24-months. Moreover, I hope for the sake of everyone that we will be able to deal with Covid-19 soon and return to something of a normal life once again. These are big ambitions and I hope that WTSM’s Reflections 2021 will record such success.
Watch this space!
ASTROPHOTOGRAPHY INDEX OF 2020
To access each blog, click on the title required below highlighted in RED:
An astrophotography image is clearly the sum of its parts, which can broadly be defined as: Equipment – Image Capture – Processing. Much attention and money is given to the first two items but it’s easy to overlook the importance of processing, I should know I’ve done it for years! With time on my hands this year during Covid-19 & lockdown, I have at last turned my attention to this most critical of items to very good effect. Hitherto I’ve used Deep Sky Stacker (DSS) for calibration & stacking, before moving to Photoshop for all other processing, which has usually produced satisfactory results. However, I’ve often thought more might be obtained from the data by using more powerful software combined with an improvement of my overall skills.
On taking up astrophotography it’s a shock when first looking at the camera’s data, which will usually produce a dark almost featureless image, represented by a very narrow, steep image histogram – a graphical representation of the tone and light collected by the exposures. This is because most of the image of the night sky will of course be dark, with precious few photons arriving from distant objects being photographed contained only within the said narrow histogram – the trick is to tease them out during processing in the so-called digital darkroom, thereby revealing the image within.
In the right hands Photoshop is an excellent tool for post processing but it’s no coincidence that most accomplished astrophotographers are using PixInsight(PI), for good reason: it is dedicated to astrophotography, is very powerful, whilst at the same time being very flexible. Unfortunately the learning curve for PixInsight is steep but from my recent experience very much worth the effort. Metaphorically speaking, I’m in the foothills of using PixInsight but now with sufficient knowledge to process images from start to finish, I have already successfully tackled complex LRGB images LBN 325 and NGC 6194. Subsequently I’ve turned my attention to re-processing old narrowband data, which first time round produced unsatisfactory results using Photoshop; this being as much the user as anything else.
Whilst PixInsight was the principal software for this re-processing, it was used in conjunction with Photoshop to achieve certain affects and other newly acquired dedicated software for specific tasks: Starnet++ to produce starless images and Topaz Denoise AIfor noise reduction and sharpening. Using the HST palette in all cases, the workflow (see table at the end) was adapted for each image depending on the characteristics of the object. Before (top) and after (below) images are shown beneath, together with links to the original blogs for more background and imaging information.
NGC 281 Pacman Nebula, August 2019: Whilst the initial HaOO bicolour image looked good I struggled to do the same with the SHO version. However, the transformation after re-processing with PI is, as they say – a whole new ballgame. Vibrant colours have emerged from the previous somewhat gloomy image, together with detailed internal structures. Although somewhat artistic in character, I particularly like the starless version which is shown at the top of the page.
IC 1805 Heart Nebula, August 2018: Like Pacman the original bicolour processing was also successful but SHO much less so. Re-processing has brought out warm colours and details around the inner edge of the heart-shaped nebulosity but it is the striking blue inner region which highlights Melotte-15 at the centre that steals the show. Here fierce stellar forces associated with superhot, young open star clusters, model the adjacent dust clouds into features analogous to those of the Eagle Nebula’s Pillars of Creation.
NGC 2244 Rosette Nebula, February 2018: The Rosette was the most difficult data to re-process and therefore turned out to be the most satisfying. Similar to the Heart Nebula, the rose-like dark nebulous outer region and bright inner edge frames the dramatic, somewhat translucent pale blue inner area. Therein billowing, cloud-like blue nebulosity shows off various internal features, which include an open star cluster at the centre and the so-called Carnival of Animals marching across the lower right quadrant. Altogether new processing has transformed this image into something rather special.
NGC 7000 North America Nebula, August 2017: Although very happy with the original SHO image processed using Photoshop, the revised version is not so much better but different. Use of the SCNR function and subsequent PI and Photoshop colour adjustments have introduced greater detail overall, as well as produced more delicate colours, especially the diaphanous blue nebulosity around the ‘Gulf of Mexico’
NGC 1499 California Nebula, October 2017: In this case re-processing has brought out greater structure throughout the nebula and, to a lesser degree, improved the overall colour. However, the nature of the object, limited integration time and relative lack of what is faint OIII and SII data has probably limited the final impact.
Frankly I found PixInsight a complete pain to understand and use initially, however, with the help of online videos, tutorials and the recently published excellent Mastering PixInsight book, I believe the results more than justify the effort and speak for themselves; overall I’m very pleased with the outcome, which far exceeds my expectations. Notwithstanding, going forwards I can’t see PixInsight being my only processing software (though it could be) but it almost certainly will now become my main choice for post processing, where necessary supplemented by Photoshop and other packages dedicated to specific tasks. It’s a case of using the right tool for the job and the wider combination outlined provides much more flexibility, as well as producing excellent results. All I need now are clear skies!
OUTLINE HST NARROWBAND WORKFLOW*
ACTION
COMMENT
Alignment & Stacking
Deep Sky Stacker
NON-LINEAR PRE-PROCESSING
Dynamic Crop
All stacks
Dynamic Background Extraction (DBE)
Gradient removal
RGB Combination
SHO Hubble palette
Linear Fit
Background Neutralisation
Colour Calibration-1
Deconvolution (sometimes)
Not used here but can be if necessary
Noise Reduction
Use ACDNR or Topaz DeNoise AI
Histogram Transformation
Non-linear stretch
LINEAR PROCESSING
Curves Transformation (CT)
Preliminary to bring out colours but not too strong
Colour Calibration-2
SCNR
Remove Green Hue
Magenta star adjustment
If present + use PixelMath script
Starnet++
Separate Nebula & Stars
(a) Curves Transformation & / or (b) Colour Saturation
Colour punch Apply Range Mask to accentuate specific areas
Photoshop – selective colours
Further specific colour adjustment
Re-combine starless & stars images
PixelMath script + experiment with proportions
Final adjustments where necessary
DBE + CT + ACDNR or DeNoise AI + Linear / Curves adjustment
I first visited the constellation of Cygnus soon after starting astrophotography, inevitably to image the Veil Nebula and North America (NAN) & Pelican Nebula, or parts thereof. As my abilities and equipment improved I’ve often returned to each of these popular targets, in the hope of obtaining a better image each time and I’m sure I will continue in this pursuit. However, such is the draw of these iconic objects that it’s easy to overlook other equally exciting targets within the same constellation.
Last year (2019) my attention was drawn to such a target in the form of DWB 111 or the Propeller Nebula, which I successfully imaged and thereby ignited my interest in the rich, very large HII-region of Cygnus (see above), within which imaging possibilities are almost endless. I therefore recently went back during this September to image two less popular targets located within the aforesaid HII-region; I had already imaged the NAN and Veil Nebula again in early September, on which occasion using my new Samyang 135mm f2 lens set-up to obtain wide-field shots.
After first imaging LBN 325 and other emission nebulae across the adjacent area, I turned my attention to a neighbouring part of the said HII-region of Cygnus, likewise found in the quadrant of Cygnus defined by the stars Deneb – Sadr – Delta Cygni. Similarly this area is full of numerous emission nebulae but furthermore here strikingly intercalated with dark nebula, star clusters and in particular reflection nebulae. Most prominent of these near the centre of the image is NGC 6914, vdB 131 & vdB32 (Main image top-of-the-page), which are conspicuously highlighted by associated bright blue nebulosity. Dotted throughout the rest of the image the use of HaLRGB picks out many other blue and rare yellow refection nebula and stars that all together make for an exciting image (Ha starless image above). Such is the quality and vastness of this part of Cygnus for potential image targets that I feel sure I’ll be coming back to this region for many years to come.
IMAGING DETAILS
Category / Object
Reflection Nebula NGC 6914
Constellation
Cygnus
Distance
6,000 light-years
Size
2.5o x 1.90o
Apparent Magnitude
?
Scope
William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera
ZWO1600MM-Cool mono CMOS sensor
FOV 2.65o x 2.0o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
EFW
ZWOx8 + ZWO LRGB & Ha OIII SII 7nm filters
Capture & Processing
Astro Photography Tool + PHD2 + Deep Sky Stacker + PixInsight + Photoshop CS3 + Topaz AI Denoise
Image Location & Orientation
Centre: RA 20h 25’ 23.097” DEC +42o 22’ 41.092” Top of image = approximately North
Exposures
36 @ 300 sec Ha + 37 x LGB 36 x R @ 180 sec Time: Ha 3hr LRGB 7hr 21min = Total 10hr 21 min
@ 139 Gain 21 Offset @ -20oC
Calibration
5 x 300 sec Ha + 10 X 180’ LRGB Darks, 20 x 1/4000 sec Bias 10 x HaLRGB Flats @ ADU 25,000
Location & Darkness
Fairvale Observatory – Redhill – Surrey – UK Typically Bortle 5-6
In September I returned to the Cygnus constellation, popular for The North America and Veil Nebula at this time of the year but elsewhere often overlooked by astrophotographers. In particular the vast HII-region that is located around the Deneb-Sadr area which contains an abundance of exciting imaging opportunities, this time my target was LBN325 which contains numerous Ha emission nebulae, a dark nebula and a supernova remnant. To capture these features at their best, I chose to shoot, process and then combine separate HaOO narrowband and RGB images for the first time.
Integrating RGB data for better star colours and narrowband data for nebulosity turned out to be tricky but by removing the stars from the narrowband nebulosity and then processing the starless image before combining with RGB image manually eventually worked out well (see top-of-the-page image). However, the narrowband and broadband data had respectively been taken either side of the Meridian without plate solving and unfortunately my manual alignment was on this occasion poor. However, with careful cropping I was eventually able to able to align and combine each of the images, though at the cost of losing 25% of the overall field-of-view which did not overlap; see full size Ha-image below with interesting features along left and right edges which had to be cropped out to align the final narrowband and broadband images.
In addition to LBN325 there are a large number of other notable features (see Image Details table at the end & Nico Carver’s annotated image below – green outline delineates areas of my image). In addition to the many Ha emission nebulae, the most noteworthy are the dark nebula Barnard 345 and a large section of the Supernova Remnant G082.2+53. Some 100 light-years in total diameter, this OIII-rich feature is unfortunately too faint to be picked out in my image, which would require significantly more OIII data to be seen. Looking further afield of the image the continuing richness of the adjoining area cannot be overstated, which is beautifully seen in Nico Carver’s accompanying image (Northwestern Cygnus by Nico Carver is licensed under a CC BY-SA 4.0 License) – an 8-pannel 46-hour mosaic! I can only dream of such work but certainly hope to return to this area again when possible, in order to enjoy more of the exquisite objects that can be found across this truly exciting area of Cygnus. But for now there’s another story about this image.
For some time I’ve known that I had to improve my processing skills and to this end purchased PixInsight software at the beginning of the year. Very few of the best astrophotographers do not use this processing software but PixInsight has a notoriously steep learning curve and no doubt like many others I gave up after a few days! I can unequivocally say that PixInsight is by far the most user unfriendly software I’ve come across in nearly four decades; there’s no denying it’s abilities but the developers clearly gave very little thought to its users. Nonetheless, spurred on by the need to improve my images and the ‘opportunity’ of more time that Covid-19 has provided us all recently, I returned to PixInsight a number of times over the summer and slowly made progress.
Cropped HaLRGB M101 practice image from scratch – using Pixel Math to add Ha has worked within the galaxy but unfortunately seems to have spread into other areas too!
Using my existing data for M101, I first spent many days working through the calibration and integration process, which can only be described as exhausting! Undeterred and in an effort to speed up matters, I moved on to Batch Processing, which though helpful only partially assists the overall task of pre-processing and inevitably put PixInsight aside again in order to find renewed enthusiasm to continue. From this initial experience I had already come to one conclusion – that I would not be using PixInsight for calibration and integration, continuing for now with Deep Sky Stacker and possibly later switching to either Astro Pixel Processor (APP) or Astro Art, both of which get good user reviews.
From the results of others it’s clear that PixInsight is a route to better images and there is no shortage of online tutorials and books but hitherto I’d not found one that worked well for me. Online tutorials by Light Vortex Astronomy are an excellent learning aid but tricky to work with on screen and Harry’s Astro Shed video tutorials were also helpful but I needed a book on the matter to read, thumb through and casually refer to when needed. Then I got lucky!
It was my good fortune that in May a new text by Rogelio Bernal Andreo (AKA ‘RBA’) Mastering PixInsight became first digitally available and then in September was published as a book. The work is divided into two well thought out and presented volumes:
A comprehensive, easy-to-follow and understand description of how to use PixInsight
A reference guide providing more in-depth information on specific PixInsight processes
The two volumes come as a boxed set, are well bound and illustrated and for the first time (from my point-of-view) form an accessible, easy to use and helpful text on PixInsight. RBA deserves every success with this outstanding book(s) which I believe will transform the otherwise torrid experience of learning PixInsight. Armed with RBA’s Mastering PixInsight, Light VortexAstronomy online tutorials, Harry’s Astro Shed and a other online videos, I’m pleased to say that I am now at last able to use PixInsight for processing and LBN325 is my first image; I should also mention Shawn Nielsen’s excellent Visible Dark YouTube channel, which demonstrates a number of very useful techniques.
As my first attempt to use PixInsight for processing, I’m pleased with the outcome of LBN 325 but realise there’s still much more to learn and, aside from the framing error, it’s clear that even more integration time is needed to get the best of LBN325 and its companions. Going forwards PixInsight and Photoshop both have their respective strengths and weaknesses and judicious use of various techniques from each is probably going to yield the best results. For now, at least, I feel the considerable time put into learning PixInsight is starting to pay off and I’ve finally turned a corner with my processing.
I’ve been very happy with my main imaging set-up for nearly 4-years: Skywatcher AZ-EQ6 GT Mount + William Optics GT81 + ZWO1600MM-Cool mono camera. Nevertheless, thoughts inevitably stray towards the big and usually expensive question – what next? Given the said equipment, a natural move is likely to be the addition of a larger telescope to get at those faint fuzzies and I have been toying with such an idea for some time – probably another refractor in the 100mm to 130mm range. However, I’ve always been held back by a number of nagging issues:
Without a sightline of Polaris for polar alignment from the main location at Fairvale Observatory, guiding is always going to be sub-optimal – I can get away with it with the smaller William Optics but a larger aperture / focal length would be more challenging;
Being a set-up / take-down observatory each night, the increased technical demands of a larger OTA would certainly take longer and in general be more difficult to undertake – as I get older moving the mount is already taking its toll on my back;
Time is short as there’s simply no getting away from the problem we all suffer in the UK – cloud and lots of it! It’s been normal to go weeks, even months without a clear night sky and as a result last year I managed to image just 18 objects over some 27 nights, of which some were only over a few hours before the clouds rolled in;
A static observatory would help enormously but my garden is unsuitable: apart from the aforesaid problem that my house obscures a northerly view, there are also houses and substantial trees and very high hedges on all the other sides.
Regretfully I have therefore always come to the same conclusion, that unless I moved house it was best to continue with my current set-up – until now! Inspired by a fascinating thread on the Stargazers Lounge Forum the solution was blindingly obvious, or at least it was once I understood there was another way, a larger field-of-view rather than larger telescope, achieved with a traditional though far from ordinary camera lens.
As a life-long photographer on land and underwater, astrophotography surprisingly came as something of a shock, as it’s just so contrasting to the aforesaid disciplines and requires quite different technical knowledge and aptitude. Of course, I’ve often used my camera equipment to image the night sky, particularly the Milky Way and started out astrophotography using a modded DSLR but otherwise did not consider that a camera lens could form the basis for my astrophotography going forwards – then I discovered the Samyang 135 f2 lens. Moreover, looking at what others achieved matching this lens with a tracking mount and mono camera, the decision to join the Samy club was a no brainer.
Located in South Korea, Samyang Optics has been manufacturing good camera lenses since 1972. Also sold under the Rokinon brand name, the Samyang 135 f2 stands out for two reasons:
The optics of the lens are top drawer, consisting of 11-elements in 7-groups using very high quality glass;
The lens is very well suited to gathering photons with a maximum f2 aperture – though most users stop down to 2.8 in order to achieve good star shapes right into the corners.
The optical quality produces sharp image quality from corner to corner but combining this with a 135mm focal length achieves an enormous 9.45o x 6.30o field of view @ f2 with a Canon 550D compared with my current set-up of 2.67o x 1.78o, opening up whole new imaging possibilities.
Inner rectangle: FOV using William Optics GT81 + focal reducer & ZWO 1600MM-Cool camera Outer rectangle: FOV using Samyang 135 f/2 & CAnon 550D DSLR camera It would take approximately a 9 x panel mosaic from the WO to cover the Samyang area!
Furthermore, this much smaller rig is lighter, easier and thus quicker to set-up and break-down. Put together it’s a powerful combination that I hope to fully exploit in the future.
Camera
Equipment
FOV
Resolution
ZWO ASI1600MM-Cool
WO GT81 + 0.80 FR*
2.65o x 2.00o
2.05”/px
Samyang 135 f/2
7.50o x 5.67o
5.80”/px
Canon 550D DSLR
WO GT81 + 0/80 FR*
2.67o x 1.78o
1.85”/px
Samyang 135 f/2
9.45o x 6.30o
6.45”/px
*Current set-up
By today’s standards this lens might be considered somewhat old fashioned with no autofocus or image stabilisation etc., but the intrinsic high manufacturing standards and manual focus are excellent for those who know how to handle such a lens and perfect for astrophotography. For such a purpose users generally either create their own rig by adapting various astronomy bits and pieces or use one of a growing number of bespoke brackets that are being made for this increasingly popular lens.
For the moment I chose to use a 3D printed bracket and integrated manual microfocuser, made by the French company AstroKraken and its founder Philippe Leca. Therein the lens is cradled by two hinged rings, which when screwed down hold the lens firmly to either a Vixen bar or Losmandy plate. The microfocuser then fits snuggly around and then clamps onto the focus ring, so that two screws on either side can be adjusted so as to push against a bridge located above and between the two rings, thus providing fine control over the focus ring; the said bridge also has a Synta fitting shoe on top to fix a finder / guide scope. Altogether it’s a neat and very effective design that provides an easy-to-use tailor made platform for the lens, which can then be combined either with a DSLR or mono camera on the back; users of mono cameras tend to recommend changing the lens’ bayonet for a screw fitting and possibly add a third ring for the camera in order to eliminate the possibility of any flexure.
Whilst the AstroKraken bracket works well, the structural layout is inevitably tight making it difficult to view the focus ring settings but once established close to focus, subsequent use of the microfocuser is excellent in finessing the job of focussing before locking down the adjustment screws. In addition, I’ve acquired a second Starlight Express Lodestar X2 autoguiding camera for use with a Skywatcher Evoguide 50ED guidescope but so far have not needed it with short exposures currently being used.
As a project for the new rig I had intended to spend the late summer imaging the suitably large Cygnus HII region but in the end conditions limited my time on this wonderful area of the sky at this time of the year and will have to wait for another time. Notwithstanding, first light using my modded Canon 550D DSLR camera of the said Cygnus area was briefly achieved at the end of July, with promising results (see above – uncropped). More recently, in early September I was able to obtain images of the Veil Nebula (see below – cropped to 70%) and North America Nebula (see top-of-the page, cropped to 80%), in all cases taken at 120sec exposures and ISO 1600. Unfortunately all integration times have been just under 60 minutes for each target and in the long run the real magic of this lens will be unlocked with the addition of a mono camera and much greater imaging times.
Looking back personally and professionally, it’s apparent to me that the concept of the big picture, metaphorically or otherwise, has played a central role in my life and is an area I like to work with; it’s the big picture that provides context, understanding and opportunity. Perhaps it should therefore not be a surprise that in the end my next step in astrophotography will now follow such a path. The detail provided with my current equipment is fulfilling and beautiful but the additional context provided by the Samyang’s extensive FOV can be more insightful and even breathtaking in scope. After something of a slow start, I’m now really looking forwards to spending more time with this new and exciting rig in the future.
Following a very poor winter period, spring has been nothing less than spectacular and provided many clear nights for astronomy, ironically made all the better by the covid-19 lockdown. With the near absence of road traffic and especially aircraft – Fairvale Observatory is badly affected by flights from nearby Gatwick, Heathrow and Redhill aerodrome – it has resulted in noticeably better seeing, as well as a quieter and more enjoyable environment overall; it’s worth noting that after experimenting with Deep Sky Stacker (DSS), increasing the Kappa-Sigma clipping parameter from 2.0 to 2.50 for the light subs, in all but the worst cases eliminated aircraft tracks in the final stacked image. Resulting from these favourable conditions, I’ve recently been able to image four otherwise difficult targets, amounting to some 40-hours total integration time, literally unprecedented conditions in the +30 years I’ve lived here.
Apart from a brief diversion imaging the Leo Triplet, my attention has otherwise been centered on the constellation of Canes Venatici, AKA the Hunting Dogs. At this time of the year the constellation starts to come into view high overhead from the east at about 10 p.m. and crosses the meridian about three hours later. Located below Ursa Major and above Bootes, the relatively small Canes Venatici hosts five Messier objects, four of which are galaxies and it is these I’ve been drawn to. From earlier test shots I determined that the M94 galaxy was unlikely to be suitable for my equipment but I did obtain and have already described images of first M106 and then M63. Notwithstanding, I had unfinished business with the last of the four galaxies, which I therefore now turned to.
In 2019 I was pleased to acquire my first ever image of the wonderful M51Whirlpool Galaxy and its smaller companion, NGC 5195. However, I noted then that the final LRGB image still needed much more integration time than just 2hr 18min. achieved, plus the addition of Ha-subs and that I hoped to return to the Whirlpool and its neighbour as soon as possible for this purpose.
It was therefore a great pleasure to image M51 over no less than seven nights in March and April this spring, which combined with last year’s data resulted in over 16 hours integration time, substantially longer than any previous image I’ve compiled before. Moreover, the quality of seeing also benefitted SNR and guiding quality, thus achieving RMS errors of at least 0.80 arc seconds or better. I did encounter some plate solving issues and had to resort to manual framing on a few nights but fortunately DSS software dealt with alignment OK and the final image is all I could have hoped for (see above + top-of-the-page cropped). Naturally the interaction of the two galaxies is the signature feature of this image but it is the improvement in general colour, detail and addition of Ha-subs highlighting regions of new star formation, that have been most transformative in portraying these objects in all their glory.
Using my current set-up it seems unlikely that the image would benefit significantly from any further data acquisition but I’d like to think I’ll return another day using a larger telescope and higher resolution with which to capture and enjoy even more detail of all these exciting objects of Canes Venatici. It is said that “it’s an ill wind that blows no good” and I am doubtful we’ll ever have such good conditions here again but for now I was delighted to be able to positively exploit this otherwise difficult time in lockdown.
IMAGING DETAILS
Object
M51 The Whirlpool Galaxy & NGC 5951
Constellation
Canes Venatici
Distance
23 million light-years
Size
11.2’ x 6.9’ 77,000 light-years (M51 only)
Apparent Magnitude
+8.4
Scope
William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera
ZWO1600MM-Cool mono CMOS sensor
FOV 2.65o x 2.0o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
You don’t have to be an astronomer to appreciate Van Gogh’s wonderful evocation of the night sky in his 1889 painting Starry Night. He knew a thing or two about sunflowers too and I’ve often stopped by the National Gallery in Trafalgar Square to take a peep at his famous painting of them. However, it was still more than thirty years after completing these paintings that we first learned that such features as galaxies and the rest of the Universe even existed beyond our own Milky Way. Since then our knowledge of the cosmos has expanded considerably and today provides no end of imaging opportunities for the astrophotographer, subject to clear skies!
Having started the galaxy season with M106 and, given the excellent conditions that prevailed throughout much of Spring this year, I chose to return to the same area of the sky again to image M63, AKA the Sunflower Galaxy. M63 has a spiral form but with no apparent central bar and in visible light lacks large scale spiral structure, although two-arm structures are noticeable in near infra-red. Instead the dust lanes are extensively disrupted producing a patchy appearance and is thus classified as a flocculent galaxy – in this case looking something like a sunflower.
As previously discussed, most galaxies are a real challenge for my equipment but an earlier experiment indicated it might just be possible to image M63, the trick would be obtaining sufficient integration time. Fortunately three clear nights approaching a new moon in April provided over 8-hours of good subs, which I’m pleased to say resulted in a decent final image after all. The background sky is less busy than I would wish but there’s nice colour in the stars and also a few very small faint fuzzies on close inspection. Notwithstanding, M63 is clearly the star of the show (no pun intended) with the so-called flocculation clearly evident and numerous random dust lanes criss-crossing the entire galactic disc.
Although in 1924 Edwin Hubble’s recognition that galaxies, such as our own, existed outside the Milky Way, M63 was discovered by Pierre Méchain and catalogued by Charles Messier in 1779, long before Van Gogh’s paintings. He might conceivably have known of its presence therefore but not what it was and would surely be inspired to see and know about the Sunflower Galaxy as we do today.
IMAGING DETAILS
Object
M63, NGC 5055 AKA Sunflower Galaxy
Constellation
Canes Venatici
Distance
29 million light-years
Size
12.6’ x 7.2’
Apparent Magnitude
+9.3
Scope
William Optics GT81 + Focal Reducer FL 382mm f4.72
Mount
SW AZ-EQ6 GT + EQASCOM computer control & Cartes du Ciel
Guiding
William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 camera & PHD2 guiding
Camera
ZWO1600MM-Cool mono CMOS sensor
FOV 2.65o x 2.0o Resolution 2.05”/pix Max. image size 4,656 x 3,520 pix
WATCH THIS SPACE(MAN) 