The Wall

SHO2 FINAL

I first had a peek of the North America Nebula shortly after I started my then nascent astronomy hobby in August 2014.  With a Skywatcher 150PL Newtonian reflector and DSLR camera, I just managed to capture the edge of this very large nebula.  It was a very poor image and obviously navigation and framing were not my strong point but the mere glimpse of such Ha nebulosity was at the time something of an epiphany.  Hitherto I didn’t know such things existed, let alone their size and grandeur and the potential to catch even a part of it on camera was very exciting – that excitement has still not left me.

NGC 7000 240914 FINAL + Red (Medium)

NGC 7000 unmodded Canon 700D DSLR | September 2015

Armed the following year with a AZ-EQ6 GT mount and William Optics GT81 refractor, I managed to image most of the ‘continent’ and ‘Gulf’ (see above), although ‘Mexico’ was still missing; the title of my related blog at the time encapsulated my emotion at the time – WOW!  Since then I have often returned to NGC 7000 and with the combination of a modded DSLR, computer control and guiding gradually improved my technique so as to obtain better images.  However, the outcome of imaging the North America Nebula this year with the ZWO1600MM-Cool mono camera has been a revelation, resulting in perhaps some of my best images so far.

I’ve recently been spending time improving post processing methods, which together with increased knowledge gained from using the new camera for more than 6-months is now starting to pay off.  Being a very large HII-region the North America Nebula responds well to narrowband wavelength filters and I therefore took Ha-OIII-SII subs, which have subsequently combined well into Bi-colour (below) and SHO images that far surpass what I’ve previously achieved.

BiCol FINAL2

I was particularly keen to capture the Cygnus Wall for the first time, located along the ‘southern California’ and ‘Mexican’ coasts – so to speak.  In both cases the Wall shows up very well in detail (below in bi-colour), with its W-shaped edge dramatically illuminated by star forming regions from within.  I am particularly pleased with the SHO image (top of the page), which apart from the Wall illustrates delicate details across the entire nebula.

Cygnus Wall BiCol FINAL

Greater care during processing is improving such images but now that I’ve experienced this new camera across a number of different objects, it is clear that further enhancements are likely to be incremental and more difficult to achieve.  The one important factor that I suspect will still provide a noticeable improvement to my images will be longer integration time, which requires plate solving.   I’m already starting to learn this process and hope to adopt its use in the New Year.  In the meantime I feel recent imaging results and especially these narrowband images of the North America Nebula mark a very satisfying climax to my astrophotography year, progress over the past few years is very evident and I’m eagerly looking forwards to 2018.

IMAGING DETAILS
Object North America Nebula – NGC 7000   
Constellation Cygnus – near Deneb
Distance 1,600 light-years
Size Approx. 50 light-years or 2o
Apparent Magnitude +4.0
 
Scope  William Optics GT81 + Focal Reducer FL 382mm  f4.72
Mount SW AZ-EQ6 GT + EQASCOM computer control
Guiding William Optics 50mm guide scope
  + Starlight Xpress Lodestar X2 guide camera & PHD2 control
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,  Deep Sky Stacker & Photoshop CS2
Exposures 18 x Ha, 8 x OIII & 8 x SII @ 180 secs  (Total time: 102 minutes)
  @ 300 Gain 10 Offset @ -20oC  
Calibration 5 x 180 sec Darks 10 x 1/4000 sec Bias 10 x Flats Ha, OIII & SII  
Location & Darkness Fairvale Observatory – Redhill – Surrey – UK      Typically Bortle 5
Date & Time 27th August 2017 @ 21.50h
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Galactic Neighbours

M31 LUM ProcessedX (Large)

I continue to be very impressed and pleased with the William Optics GT81 triplet refractor and ZWO1600MM-Cool camera combination, which has unleashed an exciting  new era in my astrophotography.  Still less than one year since acquiring the camera I continue to learn about its features, as well as master the increasing complexity of using a mono camera and filters; I am particularly pleased I waited last year for the release of the larger ZWO x8 EFW and matching 31mm filters.  Armed with this new set-up I’m working through my list of favourite targets that were previously imaged with a modded-Canon 550D DSLR, the difference is often nothing less than quite spectacular revealing previously unseen details and colours.

As the autumn equinox approached and the skies darkened again and imaging opportunities have thankfully greatly improved, subject to clear skies of course!  Whilst the scope-camera combo is excellent for larger DSO targets and especially nebulae, it is unable to tackle most of the galaxies which are usually small and require greater power than this provides.  However, there are a few exceptions, most significant of which arrives here towards the end of August if you are prepared to stay up very late.  It is our nearest neighbour M31, the Andromeda galaxy and smaller friends.  I think I’ve been quite successful imaging M31 before with a DSLR but now it was time to get to grips with the new camera and LRGB!1600-Gain-RN-DR-FW-vs-gain-716x1024

I’m new to the issue of Gain, Offset and ADU and am still experimenting with these settings on the ZWO1600.  As the camera performs quite differently to a more conventional CCD sensor, it’s fair to say that most other users, even those with CCD experience, are also on this learning curve.  After little more than a year since this revolutionary CMOS-based camera was introduced in the UK, only now are users starting to agree on suitable operating parameters.  Unity at 139 and has become the safe Gain setting but many have obtained some exciting results using either high gain and very short exposures or low gain and long exposures.  Given its size, apparent magnitude and high contrast core, it was clear that Andromeda was going to pose some new problems with the ZWO camera.

GAIN

OFFSET

ADU

0 10 400
75 12 550
139 21 850
200 30 1690
300 50 2650

Current popular guidance on ZWO1600MM-Cool settings

In view of the galaxy’s characteristics the obvious adjustment would be to reduce Gain but I continued to use my standard setting of 300 and Offset 10; the offset should be higher but for some reason I was initially successful with this level and have also conveniently stored a good set of matching calibration subs too.  My initial impression afterwards was that the subs were overcooked, blown-out in the centre and lacking detail in the spiral.  Enquires on the SGL Forum seemed to confirm that I needed to turn down the Gain for the core whilst seeking a target ADU count of about 500 to 600.  Shortly afterwards I therefore imaged M31 again but this time using two different settings for the core and the spiral:  Gain-O Offset-3 + Gain-100 and Offset-17 respectively.

Green Mud

The ‘disc of green mud’ during processing! Clearly lower Gain and Offset settings combined with shorter 30 second exposure was not working.

Despite these changes initial processing of the subs obtained from the second imaging session resulted in an even worse outcome, with the galaxy now looking more like a disc of green mud! As a result I returned to the original subs and with care and perseverance teased a decent image of Andromeda (top of page) – patience and care is everything with astrophotography, if at first you don’t succeed try and try again.

IMAGING DETAILS
Object M31 Andromeda Galaxy + M32 & M110  
Constellation Andromeda
Distance 2.5 million light-years
Size Approx. 3.17o x 1.0o or 220,000 light years
Apparent Magnitude +3.44
 
Scope  William Optics GT81 + Focal Reducer FL 382mm  f4.72
Mount SW AZ-EQ6 GT + EQASCOM computer control
Guiding William Optics 50mm guide scope
  + Starlight Xpress Lodestar X2 guide camera & PHD2 control
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,  Deep Sky Stacker & Photoshop CS2
Exposures 60 sec 40 x L + 20 x RGB  (Total integration time: 100 minutes)
  @ Gain 300 Offset 10 @ -20oC  
Calibration 5 x 60 sec Darks + 10 x 1/4000 sec Bias + 10 x  LRGB Flats  
Location & Darkness Fairvale Observatory – Redhill – Surrey – UK   Typically Bortle 5
Date & Time 28th August 2017 @ 00.00h

Eastern Promise

SHO Final

Eastern Veil Nebula NGC 6992 & NGC 6995 in SHO narrowband*

The East traditionally evokes connotations of the exotic and a promise of excitement.  This year the late Summer delivered plenty such opportunity for astrophotography combined with long, warm and clear nights, making for a productive and very enjoyable time.  Furthermore, this being the first year I’ve owned the mono ZWO1600MM-Cool camera, I’m mostly revisiting objects previously imaged with a modded DSLR and as a result am discovering details of hidden interest and beauty within the new images; on this occasion the object of my desire was the Eastern Veil Nebula in the Cygnus constellation.

Desperate to start re-imaging suitable targets with the ZWO camera, I briefly flirted with the Eastern Veil on the morning of the summer solstice this year.  But with limited darkness of any sort and coming just before dawn, imaging time was very limited.  I was still pleased with the result which bode well for longer, darker night conditions with the potential for extended imaging time.  In June I was only able to capture 18 minutes of Ha and 9 minutes each of OII and SII wavelengths, compared this time with a whopping 30 minutes for each!  OK it’s still quite short and for a standard CCD camera might only amount to one or two subs but given the unique sensitivity of the ZWO1600 operating at -20oC – itself a game changer in so many ways – the additional integration time achieved resulted in much more detailed and dramatic images than before.

Bicolour FINAL

Eastern Veil Nebula in Ha-OIII BiColour*

For the moment I’m very pleased with the outcome but it’s obvious that greater imaging time holds the prospect of even better images – although such improvements are likely to be less dramatic and more incremental in nature.  Due to practical limitations at this site I’m limited to about 2-hours dedicated imaging time each side of the Meridian and will only be able to increase the integration time beyond this barrier by using plate solving, thus enabling meridian flips during a session or cumulative imaging of the same object over different nights.  With plenty to learn and enjoy with the ZWO1600 camera, plus Orion already reappearing over the eastern horizon – my personal favourite, this is unlikely to occur before next year.  In the meantime, the Eastern Veil points towards a very promising future – Watch This Space!

NGC 6992 Bicolour The Eastern Veil Nebula detail in Ha-OIII BiColour*

Bicolour FINAL BAT

The Bat Nebula IC 1340 detail in Ha-OIII Bicolour*

IMAGING DETAILS*
Object Eastern Veil Nebula   AKA Caldwell 33      NGC 6995, NGC 6992 & IC1340   
Constellation Cygnus
Distance 1,470 light-years
Size Approx. 80’  vs Total Veil Nebula 3o
Apparent Magnitude +7.0
Scope  William Optics GT81 + Focal Reducer FL 382mm  f4.72
Mount SW AZ-EQ6 GT + EQASCOM computer control
Guiding William Optics 50mm guide scope
+ Starlight Xpress Lodestar X2 guide camera & PHD2 control
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,  Deep Sky Stacker & Photoshop CS2
Exposures 10 x 180 sec Ha, OIII & SII  (Total time: 90 minutes)
@ 300 Gain 10 Offset @ -20oC  
Calibration 5 x 180 sec Darks 10 x 1/4000 sec Bias 10 x Flats Ha, OIII & SII  
Location Fairvale Observatory – Redhill – Surrey – UK
Date & Time 19th August 2017 @ 22.38h

 

Pelican Brief

CNV00015

Located 3o west of the star Deneb in the Cygnus constellation, the North America Nebula is an emission nebula spanning some 50 light-years across, which contains numerous areas of astronomical interest that form some excellent imaging targets.  In the past I’ve usually concentrated on the ‘continent’ of North America itself but on this occasion moved my attention off the ‘east coast’ in search of the distinctive Pelican Nebula – it really does look like a pelican!

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North American Nebula (left) & Pelican Nebula | WO GT 81 & modded-Canon 550D | 2015

Separated from its neighbour by a molecular cloud of dark dust, the dominant HII region of the Pelican Nebula responds well to Ha imaging and I therefore sought to capture the ‘bird’ in this and other narrowband wavelengths.  Detail within the main cloud is further highlighted as a result of ionization from within created by young star formation, making for some pleasing and often spectacular effects.

Whilst image capture went well I was concerned by the outcome of stretching the Ha-image after stacking; the stacked image in DSS looked bright and detailed but after using Levels in Photoshop to establish the dark and light points the resulting image was somewhat dull in appearance and without the finer detail I had previously seen in DSS.  Responses to a question on the SGL Forum post made it clear that I needed to be bolder when stretching in order to achieve the desired result; I am further persuaded that I’ve been too timid with such processing techniques in the past and may need to revisit and reprocess some older data when time permits.

Pelican Images 10th August 2017 in order below:  

Ha – Bicolour – SHO narrowband

WO GT81 & ZWO1600MM-Cool + x0.80 focal reducer | 180 sec Gain 300 Offset 10 @ -20C 

10xHa + 10xOIII + 5x SII + full calibration    

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I went on to process the full narrowband data in both SHO and Bicolour, with interesting results.  The aforementioned assessment of linear stretching resulted in a much improved Ha-image, which subsequently impacted positively on the final compiled image.  However, there’s still much to consider when processing the combined channels, in particular in narrowband.

Some aspects of manipulation used during processing can have a material impact on the final image and I’ve long been concerned whether the resulting astrophotography presents a factual representation – in the case of narrowband the answer must surely be no.  Depending on the quality of data capture, detail and structure will usually be accurately recorded but subsequent ‘playing’ with the colour channels is most likely to produce a final image that is pleasing aesthetically to the photographer rather than factual; in the case of narrowband the colours available will be correctly determined by the respective filter wavelengths but there is no definitive measure of what actual colour should be in the final image.

RGB2crop (Large)In this case the Ha-image of The Pelican that was obtained demonstrated the significant improvements that can be achieved with the CMOS based ZWO1600MM-Cool camera compared to a DSLR.  I’m still learning about processing and in particular, with the plethora of options available when using LRGB and narrowband subs the issues have now escalated exponentially.  Notwithstanding the aforementioned issues I’m very pleased with my ‘new’ bird The Pelican Nebula.

SHO2 Crop (Large)

New Broom

witch

Converting from a DSLR to the ZWO1600MM-Cool camera feels in part like I’m starting out all over again and is exciting.  I’m getting used to the new field-of-view and its implications for framing, which is complicated further by using separate mono filters that can often make it difficult to identify on screen the chosen imaging target.  I’m also learning to use Astro Photography Tool (APT) for image capture, which is turning out to be an excellent programme, though at times somewhat idiosyncratic in nature.  APT contains useful Histogram and associated Stretch tools, which when applied to test shots prior to data capture can reveal underlying target detail which is otherwise unseen and thus enables suitable framing to be chosen.

With a set mount location, better polar alignment, calibrated PHD2 and a basic star alignment model established in EQ-ASCOM early in the summer, the process of imaging has now become much more efficient. After adding a few supplementary alignment points local to the target and some other minor adjustments, I have recently been able to set-up and start imaging in much less than one hour; excluding the physical set-up, imaging is possible within 30-minutes.  Contrast this with one or two hours when previously using various Synscan handset procedures and setting up the DSLR camera, I think it’s fair to say I have at last crossed the proverbial Rubicon!  Using a cooled sensor and compiling a calibration library has also been very helpful in streamlining imaging sessions, which all-in-all has made my astrophotography much more productive – qualitatively and surprisingly quantitatively too, despite all the extra subs and calibration required.

I’m currently working through familiar targets with Ha-OIII-SII subs to produce Hubble Palette based images.  It’s true to say that the use of narrowband filters has also been nothing less than a revolution for my imaging, in terms of process and results.  I’m particularly pleased that I purchased the ZWO x8 EFW and matching LRGB + narrowband filters with the new camera – 31mm parfocal filters also help minimize the need to re-focus for different wavelengths.

NGC 6960multiplelevelsonecontrast FINAL(Medium)

The Witch’s Broom (NGC 6960): WO GT81 & Canon 700D camera + 0.80x Focal Reducer | 20 x 90 sec + calibration @ ISO 800 | October 2014

It’s about 4-years since I embarked on my nascent astrophotography journey and soon thereafter I first attempted to image the notoriously difficult Veil Nebula – which of course is why I had to try.  At the time I did not know one end of the Veil from the other of this very large but faint and widely dispersed supernova and was pleased to achieve a recognizable image of the Western Veil or Witch’s Broom (NGC 6960).  This July I set out to re-image the same feature for the first time using the ZWO1600MM-Cool camera in narrowband.

Cygnus_Loop_Labeled

The Veil Nebula AKA Cygnus Loop: Ultraviolet view ref. NASA

The full extent of the Veil is broadly demarcated by the Western and Eastern Veil Nebulae, with other generally more diffuse but related areas in between.  All-in-all the entire feature is some 3o or 110 light-years across.  The ZWO1600MM-Cool has two notable features that differentiate it from conventional CCD mono cameras, those being larger sensor size and high sensitivity when using only short exposures.  Unity of the sensor is 139 but like many other new users I’ve successfully been using a much higher Gain, in my case 300 with an Offset of 10; others have reported very good results as high as 600 Gain at just 30 second exposure, which though data heavy is very useful in helping to circumvent the UK’s fickle weather conditions and the need for perfect polar alignment, which was a major factor in deciding to purchase this type of mono camera.

Being still unfamiliar with the camera’s field-of-view using the William OpticsGT81 refractor and x0.80 focal reducer combination, on this occasion I centred the Broom just above the centre of the frame, thus adding the possibility of capturing other parts of the nebula located to the east and just below the Broom in this case.  As I’ve yet to master or even attempt mosaics or a Meridian flip with plate solving, for the moment my imaging is limited by the transit period defined from about 110o east to the Meridian or similarly to the west and between a 30o to 80o azimuth, which equates to just over 2 hours per target each side of the Meridian.  The nature of the object and lack of darkness at this time of the year can often restrict this available time even further.  Notwithstanding, on this occasion I was able to obtain 20 x Ha and 18 x OII 180 sec subs in order to produce a final bicolour image.

RGB C3GxXXX

The Witch’s Broom NGC 6960 & Pickering’s Triangle NGC 6979 Ha-OIII-OIII Bicolour: WO GT81 & ZWO1600 + 0.80x Focal Reducer | 180 sec x 20 Ha & 18 OIII Subs + calibration @ Gain 300 , 10 Offset & -20C | 31st July 2017

With a good set of subs the stacked and collated Ha-OIII image has turned out well, with nebulous filament details typical of the Veil that had not previously been clear when using a modded-DSLR camera now clearly visible.  Furthermore, on this occasion the aforesaid framing included detail of both the Broom and as something of a bonus Pickering’s Triangle, altogether forming a very pleasing image.

At this stage I would usually crop the Witch’s Broom and finesse the resulting image in Photoshop.  However, following a prior line of thought and questioning on the SGL Forum, this time I tried to use the Drizzle_technique during stacking to enhance the quality of The Broom itself.  Unfortunately it didn’t take long to discover that, as so often is the case with astrophotography, drizzling is a good deal more complicated than just placing a check in the Drizzle box.

Originally developed for use with the Hubble Space Telescope, drizzle is a digital processing method for the linear reconstruction of under-sampled images, thus improving the apparent resolution of the image.  Deep Sky Stacker is an excellent piece of software and provides the facility of x2 and x3 Drizzle but unlike some commercial packages has limited memory that is used for this task.  As a result after attempting to use Drizzle whilst stacking a number of times in DSS, the process crashed at the end of each sequence.  Finally another SGL Forum query provided the answers: (i) DSS lacks memory required to stack and process the original sub using Drizzle, but (ii) Drizzle will work by applying the Custom Rectangle Mode in DSS to a select a specific, smaller area of the sub.  It took me a while to figure this out but eventually I manged to process the Witch’s Broom area of the image successfully.  I’ve concluded that Drizzle is certainly a feature worth deploying during stacking from time to time but only where the main target is poorly sampled and where the specific object will fit within the Custom Rectangle Mode defined by DSS – it should also be noted that the resulting data size also increases very substantially when using Drizzle.

RGB FINAL (Large)

Witch’s Broom (as above) + 2x Drizzle

All-in-all it continues to be a great surprise just how different and often complex the techniques are with a mono camera and filters compared to a one-shot DSLR camera, both during capturing and processing.  I was previously aware of these issues and some related shortcomings but so far the results have justified the additional effort; I’m not sure I would say the same about a conventional mono CCD camera, that requires much longer imaging times which in my opinion are not suitable for the average user and weather conditions in the UK.  I know there’s still much to master – Plate Solving + Mosaics + Meridian Flips + Sequence Generator Pro etc. – and I’ll soon need to start a completely new alignment star model for winter and recalibrate PHD2 guiding but the past few months have really been good fun and very productive.

Cosmic Nursery

bec1c7b106ed1bad345b2fe7d2fd034f--henna-tattoos-tatoo

With the summer arm of the Milky Way now starting to dominate the late evening sky I’m slowly returning to imaging DSO objects, this time literally in a new light using the ZWO1600MM-Cool camera.  Because of the inclined orientation of the Milky Way it is the lower altitude objects that first become accessible, which is unfortunate as seeing conditions will generally always be poor at these levels.

South Overview copy

However, the problem is compounded here at Fairvale Observatory by high hedges and numerous large trees that obscure much of the southern horizon below about 28and in this case also severely restricting imaging time.  It’s a real pity as the constellation Sagittarius that is located in this region of the sky abounds with some wonderful objects.

M20 Location

On this occasion my primary target was M20, the Trifid Nebula (NGC 6514). At some 28” size and an apparent magnitude of +6.3 it is just feasible with my equipment, so long as I could overcome the obstructions along the southern horizon!  Located 5,000 light-years from Earth in the Scutum spiral arm of the Milky Way, at about 300,000 years old M20 is one of the youngest star forming regions in the sky.  The feature is a combination of open star clusters, emission nebula and reflection nebula separated by dark dust lanes, that together form three lobes i.e. Trifid.  As a stellar nursery, close to the centre the most massive star is twenty times the size of the Sun surrounded by a cluster of 3,100 young stars.

M20 BiColour MasterC2HP (Large)

M20 Trifid Nebula & western edge of M8 Lagoon Nebula in Ha-OIII bicolour | WO GT81 & ZWO1600MM-Cool camera + 0.80 focal reducer | 180 sec x10 Ha x5 OIII x3 SII + full calibration Gain 300 Offset 10 @ -20C | 27th July 2017

 

M20 BiColour MasterC2HP CROP (Large)

M20 Trifid Nebula in Ha-OIII Bicolour (cropped)

Despite the limited imaging time available and other difficulties, I’m pleased with the resulting images, which have been processed in SHO and Ha-OIII bicolour.  Furthermore, just evident along the left side of the main image is the western edge of the much larger Lagoon Nebula or M8; unfortunately being even lower in the sky I don’t think I’ll ever be able to image M8 from this location.

M20 SHO Master GxHP crop (Large)

M20 Trifid Nebula in SHO narrowband (cropped)

Together with the recent success of the Eagle Nebula and Eastern Veil, things are shaping up well for astrophotography once again as the Milky Way and other features pass across the night sky over the coming increasingly dark weeks.  I’m certain to return to M20 again as it’s a wonderful object, hopefully from a better vantage point next time that will allow imaging of some of its neighbours.  I have long been aware of M20 and in my ignorance was going to call this blog Gardener’s World but now realise that it is the Trifid not Triffid nebula!

330px-Booletriff

That’s Trifid not Triffid!

 

The Dutch Gadget

IMG_8370x (Large)

I have just finished reading J.L. Heilbron’s biographical tome on Galileo, which though very interesting I found a difficult book and somewhat academic in style.  In 1609 Galileo became aware of a Dutch spectacle maker’s device that made distant objects appear closer.  He subsequently became known for developing the so-called ‘Dutch Gadget’ into what we now know as the refracting telescope and moreover, applying its use to understanding the Solar System with the discovery of Jupiter’s four largest moons, confirmation of the phases of Venus and the observation and analysis of sunspots; the word telescope was subsequently coined in 1611 from the Greek tele “far” and skopein “to look or see” i.e. far-seeing.  In so doing he also helped to confirm the then controversial truth of the heliocentric astronomical model, whereby the Earth and planets orbit the Sun.  Against this background it is no surprise that Galileo is today much revered by mankind and has become known as the father of observational astronomy.

GalBook

Drawn into the complexity of obtaining images of the Solar System and beyond, it is the curse of astrophotography that we inevitably neglect observing the spectacle itself.  Notwithstanding, I am sure that Galileo would understand the power and beauty of today’s astrophotography, which in its own way is producing a quantum leap in our understanding of the Universe comparable to the impact of the original application of the telescope.

This summer the Solar System will hopefully provide both good observational and astrophotography opportunities here at Fairvale Observatory: Jupiter, Saturn, Comet C/2015 V2 (Johnson), the Perseids meteor shower and the Sun – sadly though I will not witness next month’s solar eclipse which takes place mainly over North America.  During recent summer months the lack of astronomical darkness, short nights and absence of DSOs has frustratingly continued to limit potential imaging targets for my new ZWO 1600MM-Cool camera but utilising a period of good weather there have recently been a few fleeting opportunities just before dawn related to the appearance of the summer arm of the Milky Way on the eastern horizon.

solstice sky

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NGC 7000 The North America & Pelican Nebulae WO GT81 + modded Canon EOS 550D + FF | 30 x 120 secs @ ISO 1,600 + calibration | 19th September 2015

I first imaged the North America Nebula (NGC 7000) in 2014 and have since returned each year to image the nebula or its various parts using a DSLR camera.  Being a very large Ha-object the nebula is an ideal target for the ZWO1600MM-cool camera and I have been anxiously waiting its arrival again this year.  On this occasion, early on the morning of the summer solstice, high in the sky and 90o east the nebula was only just visible from my location, being very close to the roof-edge of my house!  Consisting of just six Ha-frames plus three OIII and SII taken just before dawn broke, the resulting image was never going to be my best but is nonetheless interesting in SHO format and quite different to previous DSLR images.

NGC 7000 BiCol (Large)

North America Nebula in Ha-OIII Bicolour

RGB L2C3 GxL3 Hub1 HPx

North America Nebula in SHO

At the other extreme, located low on the southern horizon and only briefly visible as it passed between the trees at the end of my garden is the Eagle Nebula AKA M16, home of the Pillars of Creation.  At 7-arcminutes in size and an apparent magnitude of +6.0, the nebula is at the lower end of possible for my set-up and at some 27o altitude with just 40-minutes imaging time between the trees it was a challenging target.  Notwithstanding, I’m pleased with the Ha and SHO narrowband images obtained, which quite clearly show the Pillars too.

M16 SHO1 (Large)

M16 Eagel Nebula in SHO: William Optics GT81 & ZWO1600MM- Cool & Field Flattener | 6 x 180sec Ha, x3 OIII, x3 SII Gain 300 Offset 10 + full calibration | 21st June 2017

As astronomical darkness is now slowly returning and with clear skies and weather permitting, I hope to attempt longer imaging sessions of both these and other targets during the rest if the summer and into autumn – I might even get to see M16 again as it eventually emerges from the other side of the trees!  Thanks to the development of the Dutch Gadget and modern cameras it is now possible for amateur astronomers to image such spectacular objects – I’m sure Galileo would be impressed and highly approve.

Another Side Of the Veil

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Veil Nebula / Cygnus Loop WO GT81 & modded Canon 550D + FF | 30 x 180 sec exposures @ ISO 1,600 | 19th September 2015

I first imaged the Western Veil in October 2014 and return each year to the so called Witch’s Broom and other parts of this faint supernova remnant that stretches over 3-degrees of the night sky for the next four months.  Located in the Cygnus constellation, the Veil Nebula is high in the sky and at this time-of-the-year is only just visible late in the night being some 80o east of The Meridian; short nights and lack of darkness further complicates imaging at the moment.  However, with the weather set fair and having just completed some other good targets, I couldn’t resist a few frames of the Eastern Veil using the new ZWO1600m-Cool camera and narrowband filters before going to bed.

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Eastern Veil Nebula (NGC 6922 & 6995): WO GT81 & modded Canon 550D + FF & guiding | 10 x 300 sec @ ISO 1,600 + darks | 11th September 2016

With Nautical Darkness due to end at 2.40 a.m. imaging time was at a premium. In the event I managed just 40 minutes, towards the end of which the sky perceptibly lightened – it was after all mid-summer day and the Summer Solstice beckoned!  The limited imaging time inevitably impacted on the quality of the final image but I am nevertheless pleased to have seen and imaged another side of the Veil nebula so soon in the year on 21st June – certainly the sensitivity of the camera helped a lot in achieving this.

Veil HSO Hub

HSO

Veil Bi Col Hub

Bi-colour Ha+OIII+OIII

Eastern Veil Nebula – narownband images: All images taken using WO GT81 + Field Flattener & ZWO 1600MM-Cool camera + either Ha (6 x 180 sec), OIII 3 x 180 sec or SII 3 x 180 sec at -20C set at Gain 300, Offset 10 & full calibration | 21st June 2017 

I am still experimenting with narrowband imaging and therefore using colour mapping processed the three wavelengths into three different final image formats.  The HSO and Ha-OIII Bi-colour are interesting but my favourite is the SHO version shown below, which shows interesting and attractive details of the Veil’s nebulosity in ways that were previously not possible with a DSLR camera.  Though short, it was a very productive evening for imaging and for a variety of reasons will be a night to remember for a long while.

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Eastern Veil Nebula in SHO – For Will

 

A New Palette

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It still remains early days with the new ZWO 1600MM-Cool camera but the initial signs using the narrowband filters have been very promising and frankly good fun.  I’ve been surprised at the benefits gained using these filters and especially the new and exciting possibilities it introduces to imaging. But there’s more.

When first using a digital camera for astrophotography it came as a surprise to discover that the colours come from an RGB Bayer Matrix placed in front of the sensor.  The so-called One Shot Colour camera or OSC, provided me with many decent images and when I recently started to think about getting a better camera another OSC seemed the way to go.  Their major benefit is that you are able to just take, as it says, one shot – or multiple colour shots for stacking.  Of course there’s still much to learn when starting out but the process is relatively simple and a decent set of subs and calibration frames can be obtained in a few hours or less; subsequent processing is also straightforward with one set of subs and no more than three sets of calibration frames.

Notwithstanding, when looking at more specialized OSC cameras, it soon became clear that the benefits of moving from DSLR were limited.  Another surprise with astrophotography is that the best images are obtained using a mono camera, in combination with colour and if required narrowband filters.  Hitherto, this has meant precise guiding in order to obtain long exposures using a very expensive CCD camera.  However, last year everything changed with the introduction of completely new technology in the form of a cooled CMOS camera, which I and the astrophotography community are currently getting to grips with – the aforementioned ZWO ASI1600MM-Cool.

Whilst more complex to use than a DSLR, this camera seems to be something of a game changer for astrophotographers in that: (a) it has a larger more sensitive sensor than a CCD camera, (b) it’s cheaper (though not cheap), (c) because of its sensitivity imaging requires only relatively short exposures, thus reducing the need for ultra-precise guiding as it gathers light more quickly than a conventional camera.  It was the latter feature that convinced me to go ahead with the camera and it is already clear this was not a mistake.

I often complain about the excessive cloud cover we suffer here at Fairvale Observatory, which can often prohibit imaging for weeks or even months on-end.  The advantage of imaging quickly when the clouds do eventually part is therefore a major factor for me.  If the camera has one problem it’s probably the vast quantity of data generated, putting huge demand on computer memory and processing power – but it’s worth it.

LRGB

LRGB imaging is the main format used by most advanced astrophtographers, after all the resulting colours and detail achieved can be spectacular and it was now time for me to give it a try.  I was astonished to learn that some 80% of the detail in an image is in the luminance and only 20% colour, so the advantage of LRGB imaging becomes immediately apparent.  I also purchased the ZWO x8 EFW and matching 31mm filters with the camera and initially had some problems getting it to work.  However, once sorted it has been a pleasure to use and makes image sequencing with different filters a piece of cake.

At the moment I’m using Astro Photography Tool (APT) for capture and apart from my own lack of LRGB imaging experience and some misunderstandings of the software, it works very well.  A full LRGB sequence is easy to set-up beforehand and after that the imaging automatically looks after itself!  I carry out most of the calibration frames manually but this too is generally quite easy; I did struggle at first with the flats, which is a quite different method compared to a DSLR but once I got the hang of the APT Flats Aid – courtesy of the APT Forum members – all was OK.

Notwithstanding, at first I was concerned by large concentric light and dark halos in the flats.  I have long used the combination of a flowerpot, LED and T-shirt for taking flats, which has always worked well.  I therefore expected the flats from the new camera using APT would not be a problem.  However, as mentioned taking flats with this camera is a whole new ball game which has taken some time to master, or at least learn.

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The flower pot flats set-up has always worked well before.

Unlike the DSLR, which just requires changing to the AV mode, it is necessary to calculate an exact exposure – to five decimal places – using a mid-range ADU setting of between 20,000 and 25,000 for each different LRGB filter.  Sounds awful and it does generate a lot of frames but now I’ve got the hang of the Flats Aid it is much easier and very effective; on average I have so far found the required exposures vary from 0.00145 sec to 0.00792 sec.  I did discover some minor light leakage in the optical train when testing the flats taken in daylight but by doubling up the T-shirt material and adopting a more careful set-up of the flower pot directly in front of the telescope object lens, the halos now seem to have disappeared.

The other new ‘toy’ with this camera is cooling.  Despite the camera’s low noise and high sensitivity, like all digital cameras there is an inevitable amount of unwanted signal and currents created by the sensor.  Apart from applying calibration frames, this problem can be significantly reduced by cooling the sensor when imaging.   APT also has cooling and warming aid controls to avoid thermal shock but at first I struggled to get these working – turns out I forgot to plug the power lead in!  After that it has worked like a dream and I am now routinely imaging at -30oC.  The one drawback is that cooling down and warming up adds another 10 or 15 minutes to the set-up and take-down times, which can be annoying at 2.00 a.m. when you want to get to bed!

Unfortunately, now I have this camera working suitable imaging targets are in short supply for the moment.  At first I was able to carry out some narrowband imaging of the remaining late winter nebulae just before they disappeared for the season but I must now wait for a few months until later in the year for similar objects to appear again. Meanwhile, whilst the night sky in spring abounds with some wonderful galaxies, most of these are really too small for my set-up to resolve properly.  However, in the absence of larger DSO objects I have had to make do with these and have been pleasantly surprised by some of the results obtained.

The outcome of Leo Triplet and Markarian’s Chain were particularly good and demonstrate the superior abilities and power of the camera.  Compared to the Canon 550D, when used with the William Optics GT81 refractor and a x0.80 field flattener, the ZWO 1600MM-Cool’s sensor produces a notably larger image with much greater sensitivity.  As a result detail of all three galaxies that form the Leo Triplet M65, M66 and the end-on view of NGC 3628 is quite apparent and in another image, the spirals of the very small M61 galaxy can be clearly seen, though the quality is poor.

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Leo Triplet – M65 (top right) M66 (centre right) NGC 3628 (lower left) Leo Constellation: William Optics GT81 & ZWO 1600MM-Cool + x0.80 field flattener | 60 sec 20 x L, 5 x RGB + full calibration, Gain 300 Offset 10 @ -20C | 21st March 2017

As expected the size of the data set from LRGB imaging with the camera is prodigious and furthermore, requires great care to organise before processing if mistakes are to be avoided.  In the case of Markarian’s Chain I experimented with binning – only to learn later that it has no effect with CMOS sensors – which reduced the file size of the RGB and calibration images.  Nonetheless, in all there were still 140 images with a combined file size of 1.6 Gigabytes!  Notwithstanding, the benefits of LRGB imaging with this camera and EFW outweigh such problems and nowadays an extra storage disk is relatively inexpensive.  Only processing power could perhaps be a problem if using an older PC but my 64-bit + i7 chip +16 GB RAM laptop computer has so far dealt easily with data processing very well.

lrgb data

The difference between imaging and processing with a DSLR and the ZWO CMOS mono camera has been much greater than I anticipated and required more adjustment which I am still dealing with – the learning curve is steep!  Notwithstanding, the experience previously gained using a DSLR has proved invaluable and I would not like to take-on LRGB imaging from scratch; I’d like to think that my adage of walk before you run once again has paid off.  This camera is very exciting and I am confident that when the autumn and winter skies eventually return the new palette now in my hands will reap great rewards – can’t wait.

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Markarian’s Chain | Subs 60 sec – see table for details Gain 300 Offset -30C | 18th April 2017

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M61 piral Galaxy in Virgo Cluster | William Optics GT81 & ZWO 1600MM-Cool + x0.80 field flattener | L 30 x 40 sec RGB 3×20 sec + full calibration Gain 75 Offset 15 -30C | 2nd April 2017

Brave New World

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In my quest to understand astronomy and in particular the big picture, I have just successfully completed another MOOC course at the University of Edinburgh on the Higgs Boson and particle physics.  From earlier studies which included the Special Theory of Relativity and the Universe, the next step was obvious: moving from the very big to the very small in order to better grasp where we might be with the elusive unified theory and I was not disappointed. An added bonus to the course was the participation of Professor Peter Higgs himself, in which he discussed how he had arrived at his conclusions and the development of subsequent matters that led to the actual discovery of the Higgs Boson at the Large Hadron Collider in Cern, Switzerland in 2012; watching and listening to him speak felt like having a personal chat with Einstein and was quite a privilege!

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A chat with Professor Peter Higgs!

Frankly I found the nature of the subject very difficult and at times bewildering but its potential impact on astronomy was finally something of an epiphany for me.  The Higgs and related items results in two profound results:

  • There was no Big Bang.
  • The existence of a multiverse, of which our Universe is but a part.

I am not sufficiently able to articulate how these conclusions are arrived at nor is this the place, but when the full content of particle theory, the Higgs, General Relativity are applied to cosmology, the aforementioned outcome is, like all good science, simple and beautiful – click here for lecture notes Higgsmooc part1  + Higgsmooc part2  and accompanying presentations 7.11_Quantum Vacuum_& Cosmology + 7.12_The HB_scalarfieldsand inflation.

I’m pleased to say there have also been other breakthroughs for me since achieving first light with the ZWO 1600MM-Cool CMOS camera.  I am still at the experimental stage and with the spectacle of the winter sky rapidly departing, suitable objects are much more limited, with the few remaining HII objects low and very far to the west of the early evening sky.  However, before the Milky Way disappeared completely I managed to obtain some useful imaging experience by targeting some old favourites.

M42

Passing Shots: Orion & Rosette Nebulae

Having already battled a number of issues with the new camera – basic LRGB image capture, using Astro Astronomy Tools, achieving focus, guiding, alignment, processing and post-processing – for the moment everything has come together, including some warmer nights and clear skies.  Over a few evenings I therefore undertook imaging in LRGB as well as Ha, OIII and SII, with some excellent results that augur well for the future.

The camera’s sensitivity and ability to image at short exposures enables much less imaging time than conventionally used with CCD cameras – one of the reasons I decided to purchase this camera.  In addition, shorter exposures make perfect alignment and tracking less important, though still a desirable set-up.  The downside is it produces a prodigious number of images, which leads to a somewhat challenging processing burden – but it’s worth it.

Despite my DSLR experience, CCD processing and especially post-processing, is significantly more complex.  I was surprised to find only one decent online video on LRGB processing by Rankin Studio, without which the task would have been even more difficult and taken much longer to learn – thanks David.  Ironically I have found narrowband processing easier, probably because there are just less filters and resulting image sets required, however, the restricted wavelength also provides whole new opportunities that I’ve already started to exploit.

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Orion Nebula + M43 & Running Man Nebulae in Ha: William Optics GT 81 & ZWO 1600MM-Cool + x0.80 field flattener | 15 x 180sec Gain 139 Offset 21 @ -18C & full calibration | 25th March 2017

Just before they disappear from our night sky until next winter I was fortunate to be able to image both the Horsehead and Orion nebulae, everyone’s favourites and I’m no exception.  With limited time available in the early evening sky it was only possible to capture a limited number of images before it moved outside my view in the west but even with these few images the power of the camera has already become self-evident.

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Horsehead Nebula in Ha: William Optics GT81 & ZWO 1600MM-Cool + x0.80 field flattener | 19 x 180 secs Gain 139 Offset 21 @ -18C & full calibration | 27th March 2017

Given the need to use less filters and thus less time I have started out with narrowband imaging – as a completely new medium for me that holds great promise aesthetically and scientifically, I was also keen to give it a try and on this occasion used Ha and OIII.  Having sorted an earlier problem with the EFW managing the filters is a breeze and can easily be automatically sequenced in the APT capture software.  Notwithstanding, as previously indicated image capture is really only just the start – though good data is always the key to the final image – and processing and post-processing is both complex and takes considerable time.

M42 Bicolour & balance

Orion Nebula in bi-colour: Ha red channel + OIII green and blue channels

On this occasion the individual Ha subs are themselves very revealing, showing new details when compared with previous DSLR images.  But it is with the bi-colour image that the exciting opportunities provided by using narrowband imaging become apparent – I can see I’m going to enjoy this!  I’ve also taken the opportunity to further explore and understand the nature of these types of images and their constituent parts by manipulating the colour channels, with some startling results.

NGC 2244 HOS-1LCLCrop (Large)

Rosette Nebula in HOS: William Optics GT 81 & ZWO 1600MM-Cool + x0.80 Field Flattener | 15 x 180 sec Gain 300 Offset 10 Ha, OIII & SII @ -20C + calibration | 24th March 2017

Not far from M42 is another of my favourites which I’d already used to achieve First Light with this camera using Ha – the Rosette Nebula (NGC 2237, 2238, 2239, 2244 & 2246).  This time I decided to use all the narrowband filters – Ha 656nm, OIII 672nm, SII 500nm all 7nm bandpass – and subsequently experimented with processing using the Hubble Palette with stunning results.  As the name indicates, this technique was originally developed for processing images taken with the Hubble Space Telescope which put simply, uses different mixes of each narrowband filter in different processing channels e.g. Ha in the red channel, OII in green and SII in blue, for short known as HSO.

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Rosette Nebula in  SHO

The outcome of my new adventure into narrowband imaging has been nothing less than a revelation.  Like so much of my preceding astroimaging, I knew about much of it before but doing it yourself and seeing the results is both exciting and very satisfying; like Peter Higgs I feel I have entered a new world!