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

 

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New Broom

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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.

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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.

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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.

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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.

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

 

Overspill

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After months of cloud followed by 3-months of lost imaging time due to a mysterious camera / mount control problem, I was on the verge of throwing in the towel by August.  But then I sorted the problem, started guiding and as if by magic, with a prolonged spell of good weather managed 7-nights of astronomy between 23rd August and 13th September; such was the intensity I was able to work over consecutive nights and by the end quite exhausted but happy.

Under clear skies and warm nights I could operate in just shorts and a T-shirt, a hitherto unknown experience at Fairvale Observatory.  In such comfort I was also able to experiment and optimize the equipment set-up further – oh, if it could only be like this always.  Of course I did not miss the opportunity to chase some night sky objects as well, imaging 11 targets all-in-all, sometimes on more than one occasion.  It was a glorious time which has since taken time to organise and process.

Top left – NGC 6905 Blue Flash Nebula in Delphinus constellation 42″ x 35″ mag +11 26th August; Bottom left – NGC 6781 planetary nebula in Aquila constellation 1.8′ +mag 11.8 23rd August; Middle M57 Ring Nebula Lyra constellation 1.4′ x 1.1′ mag +8.8 13th September; Right M57 23rd August

A number of these images have already been reviewed in Forbidden Fruit and The future is not what it used to be but, such was productivity that for the record I’ve collected the overspill here.  Inevitably targets reflected what was about and in sight from this location at the time but were nonetheless diverse in nature, ranging from the Witch’s Broom to planetary nebulae, the Andromeda galaxy and, making use of the otherwise frustrating monthly occurrence, the Moon.  Features such as M57 and NGC 6781 are intrinsically too small for the William Optics GT81 and Canon 550D, filling significantly less than 1% of the original image but after cropping both are evident in the final picture.

Top Left – M15 Globular cluster Pegasus constellation 29th August; Top Right – Q1 Moon 23rd August; Middle Right – NGC 6960 Witch’s Broom Western Veil Nebula; Bottom – M31 Andromeda Galaxy 26th August

These images are not particularly memorable but it was a fun time and I will remember the enjoyable experience for a long while.  Of course, the cloud has now returned and since passing the autumn equinox night temperatures have plunged into single figures.  On the plus side, Orion is on its way together with all the other photogenic objects that characterize the winter night sky – can’t wait!

The future is not what it used to be

 

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If I’m honest my astrophotography has so far often been – never mind the quality feel the width!  That is to say, I have tended to chase objects – nebulae, galaxies, planets, solar – in order to learn about my equipment and the night sky as well as just have fun recording images of these distant worlds.  Nothing wrong with that is there?  It’s not that I don’t aspire to obtaining the best image possible and I have made good progress since starting out but I’ve often felt constrained by circumstances.

Although I’ve generally been happy with my images, it’s a fact that there are a number of factors that altogether make astrophotography difficult, especially here at Fairvale Observatory:

  • Poor weather & persistent cloud cover
  • The Moon
  • Buildings & trees obscure sightlines
  • Light pollution from Gatwick airport
  • Numerous aircraft passing overhead
  • Equipment problems
  • Software problems
  • Equipment and software failures
  • Equipment limitations
  • Need to assemble equipment each time
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Bad weather, frequent cloud cover, limited sightlines, aircraft trails and the inevitable monthly occurrence of the Moon limit imaging opportunities here.

Under these circumstances I usually need to grab what I can, frankly it’s a miracle I’m able to achieve anything sometimes; Met office statistics for the six-months period from September 2105 showed cloud cover was a record 68% compared with an historical average of 32% for that time of year, as a result it was unusual to be able to undertake astrophotography more than once month, if that!  Wherever possible I therefore have to target those items that I can improve easily, quickly and cheaply dealt with, which is mostly equipment.  Buoyed by renewed enthusiasm from my recent autoguiding success, I now intend to concentrate on changing some key items that I hope will eventually bring about more noticeable improvements.

sign2For a while I have been thinking about getting a larger telescope, in order to get to those faint fuzzies that are beyond the capabilities of the otherwise excellent William Optics GT81.  As usual the choice is a minefield of possibilities, each with inevitable imaging pros and cons!  I started thinking about a Ritchey Chrétien or Schmidt Cassegrain but I have really appreciated the qualities of the aforementioned WO GT81 and am now erring towards a larger refractor.  However, after further consideration I am now considering a change of priorities.

In September I was fortunate to attend a presentation on image processing by Nik Szymanek who, it has to be said, really knows his onions when it comes to astrophotography; I was intrigued and impressed to find out he also hails from my neck of the woods when I was a teenager in Essex and is an accomplished rock drummer – something I also used to meddle with in the past – what a geezer, as he would say.  The talk was very instructive and I am now ploughing my way through Nik’s fabulous book on the subject called Shooting Stars (published in magazine form by Astronomy Now).  Such personal, first-hand and relevant guidance is difficult to find in astroimaging and the book has a wealth of really practical information and useful advice that I wished I’d known sooner.  Good equipment is important but in the world of digital imaging the significance of processing cannot be overstated.  It’s a dark art alright (no pun intended) but Nik’s work has strengthened my resolve to improve my processing knowledge and I’m even more determined to raise the bar during the forthcoming winter.

20160708-shooting-stars-for-storeFollowing Nik’s talk and listening to others, the penny that has now dropped is that for the moment it’s not the telescope but the camera that needs changing.  After careful thought it’s apparent that I already have very good set-up, yes a bigger aperture would be good for those smaller fuzzies but the 81mm apochromatic refractor I already own is an outstanding telescope that still has much potential when combined with the AZ-EQ6 mount and now autoguiding.

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The addition of a modded DSLR at the beginning of last year had a significant impact on my images, especially with Ha dominant DSOs which I literally saw in a new light using this camera.  I have continued with the DSLR for a number of reasons but mainly because I am familiar with such cameras which are relatively easy to use and produce reasonable results when starting out with astrophotography.  However, listening to Nik and reading the forums and elsewhere, I have come to accept that the best way forwards should now be a CCD-type camera.  As a result I am deep in my research of CCD issues and possible cameras – this could take some time and won’t be cheap!

The operation of CCDs is quite different to a DSLR and I’m sure will involve a whole new period of pain but it’s clear that this is the best route for now if I am to significantly improve my astrophotography.  Other than the technical challenges CCD imaging presents, I am however concerned about the greater number of frames needed for LRGB + calibration and how that’s going to work with the weather restrictions and other problems I have but it’s got to be worth a try.

However, before setting out on this daunting task I first slewed the camera towards a few familiar objects just to experiment with guiding and assess the benefits it might bring to my imaging in the interim.  A spell of unusually good weather in late August – early September was too good to miss and with guiding I was able to achieve exposures of up to 8 minutes.  However, for the moment I continued to limit the number of Subs and calibration frames just to ensure I could shoot more objects in the available time, plus you never know when the next bank of cloud will roll in – old habits die hard!

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Looking at the results below demonstrates my progress when compared with earlier images but the limited number of frames and calibration has probably restricted the full benefit of what might be gained from guiding and some shots remains quite noisy. Nonetheless, I now have high hopes that the potential is within my grasp to make real progress in achieving better image quality.  I am not convinced I have yet reached a turning point but I am well positioned to navigate the tasks required to get there, which are now more clearly understood and in my sights or should that be RDF – watch this space!

M31 Andromeda Galaxy

M31 DSS2 30 sec ISO800 170814crop

WO GT81 + unmodded Canon 700D & FF| 10 x 30 secs & ISO 800 | August 2014

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WO GT 81 + modded Canon 550D + FF | 9 x 120 secs @ ISO 1,600 | 19th September 2015

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WO GT81 + modded Canon 550D & FF & PHD guiding | 10 x 300 secs @ ISO 1,600 calibration | 8th September 2016

NGC 6905 Western Veil Nebula – The Witch’s Broom

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Canon 700D | 20×90 sec + darks.bias/ flats @ ISO 800

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WO GT81 + modded Canon 550D + FF & PHD guiding | 5 x 300 secs @ ISO 1,600 & calibration | 8th September 2016

NGC 6888 Crescent Nebula

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WO GT81 + modded Canon 550D + FF | 19th October 2015

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WO GT81 modded Canon 550D + FF & guiding | 10 x 300 secs @ ISO 1,600 & calibration | 11th September 2016

NGC 6992 Eastern Veil & Bat Nebula

NGC 6995 Stacked1-22 (Large)

Eastern Veil Nebula – NGC 6992 (right) & NGC 6995 (left). WO GT81 + Canon 700D & FF | 29 x 120 secs + darks/bias?flats @ ISO 1,600

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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