Boreal Breakthrough

M81 A (Large)

I have often written about imaging difficulties here at Fairvale Observatory, which apart from overflying aircraft from Gatwick and Heathrow airports, 24/7 helicopters from Redhill aerodrome and general light pollution, also consists of numerous sightline obstructions in the form of large trees to the east and south, high garden hedges and the complete obstruction of the north sky by my house!  I have toyed with the idea of moving onto the lawn so as to look back northwards over the house but was concerned by all the faffing about to get the equipment down and back up a flight of steps, as well as added complications with equipment control and dew problems; I concede that many do operate successfully in this way but with plenty of other problems to cope with, I like my hobby to be as easy and convenient as possible.

Last year I enjoyed working outside during the summer months – notwithstanding the lack of darkness during much of this period – and therefore over the past winter finally considered how such a garden-based set-up could be achieved, primarily for use between May and September.  The resulting Plan-A was to place three paving stones within the lawn to support the tripod and run a USB-cable back to the house for control.  However, after recently expanding a small paved area outside the shed at the end of the garden and looking at the potential sightlines from this location, it was obvious that a Plan-B set-up here could also work.  Whilst not quite as good viewing angles as the original location, there are a number of other worthwhile benefits:

  • Being off the lawn on paving it seemed likely that dew could be less of a problem;
  • Working on the paving around the mount would be more convenient and dry;
  • By clearing out the adjacent shed it could be used as a dry location from which to control the equipment.

And so early in May I set about establishing Plan-B and soon afterwards putting it to work.

Pan1 Comp (Medium)

The view from the shed looking northwards is surprisingly quite good (see above) and I don’t know why I hadn’t considered this before. There are a few large trees to the north east, a high hedge along the western boundary and of course my house is still somewhat in the way but altogether it’s not too bad and for the first time I have a clear view of Polaris, as well as a whole new plethora of imaging targets!  Whilst this direction looks directly towards south London, being on the southern slope of the Greensand Ridge the worst of the city’s glow is fortunately obscured by the hill.  Furthermore, it is ironic that my house and the hedges also provide considerable protection from the local street lights, which I’m pleased to say are now turned off after midnight anyway.


Local equipment layout the same as previously

I cut-back some of the adjacent vegetation to improve sightlines and ran a power cable from the house to the shed otherwise it’s exactly the same set-up which was being used at the main, south looking location on the patio by the house.  I looked into WiFi-control of the equipment but from the experience of others concluded it could be unreliable and instead considered using Teamviewer software via a USB Cat-5 repeater cable from the mount / shed computer to a second computer in the house.  However, given the distance of some 30 metres I finally decided to adopt a more robust LAN Cat-6 ethernet cable for this purpose. Unfortunately whilst this had worked successfully during testing in the house, I have so far been unable to get it to work outside and for now have had to operate the equipment from inside the shed, which has nonetheless proved to be a comfortable and effective alternative.

Being lazy and cautious about changing too much about the set-up, I levelled, aligned and reset the new location data of the tripod but kept all other settings the same for now.  I realise this is not ideal but initially just wanted to experience the new location and north sky to understand what was possible within the given field-of-view and identify any obvious problems.  Fortunately a settled period of good weather allowed me to try out the new location soon thereafter.

North Sky ViewX

White area shows optimum imaging area from Fairvale Observatory South – AKA ‘The Shed’

What I hadn’t expected on first use was that slewing and tracking would become more difficult and takes noticeably longer at higher latitudes, especially approaching Polaris.  Following subsequent enquiries and with some further thought it now makes sense.  At higher latitudes near and above about 70 degrees as the lines of Longitude are closer together, it makes the RA slew rate bigger and bigger the closer you get to the North Celestial Pole.  Of course the celestial pole is not coincident with the terrestrial pole, which means that those objects within the latitude of 90o minus the observer’s latitude – in my case this equals 39o – means that all those objects above 39o will be circumpolar from my point-of-view i.e. will rotate over the year around North Celestial Pole.  This is basic astronomy but hitherto I had not considered the implications for tracking and guiding before and will need to bear it in mind when selecting targets in the future.

M81 B (Large)

I had one particular target in mind but as it was only viable much later in the night, on this occasion I chose to start imaging the north sky for the first time with Bode’s Galaxy AKA M81 and the nearby Cigar Galaxy AKA M82; for comparison using low gain, long exposure on the first night (top of the page) and high gain, short exposure (below) on the following night.  Given the target’s DEC position of 70o I soon discovered the aforesaid tracking difficulties, which resulted in the RMS guiding error varying from 3’ to 20’ and deleterious consequences for the images!


Whilst I’m pleased with my very first north sky images, it is obvious I’ll need to return again with better guiding and much longer integration time.  On a positive note the general set-up worked very well and the shed provided an excellent place from which to operate the control and image capture equipment.  Furthermore, despite a few restrictions the overall view of the northern night sky is good and holds much promise for future, hitherto inaccessible imaging objects.  As a result of establishing this new site I intend to name the new north looking location Fairvale Observatory South or ‘The Shed Observatory’ (see mosaic above) and the principal, south looking location by the house Fairvale Observatory North or ‘The Patio Observatory’.  Altogether this marks a major breakthrough for my astronomy and I eagerly await the return of astronomical darkness on 20th July onward.

AstroNet ResultX

Objects Bode’s Galaxy M81  &  Cigar Galaxy M82     
Constellation Ursa Major
Distance M81  11.8  &  M82  11.4 -12.4 million light-years
Size M81 26.9’ x 14.1’   &    M82 11.2’ x  4.3’
Apparent Magnitude M81 +8.0  &  M82 +8.4
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 + PS2,  Deep Sky Stacker & Photoshop CS2
Image Location Centre Image-B    RA 09:55:13.46    DEC 69:21:08.36  (19/0518) 



A 18/05/18   10 x 180 sec L  + 5×180 sec RGB  (Total time: 75 minutes)    @ 139 Gain   21  Offset @ -20oC

B 19/05/18   45 x 60 sec L    + 15 x 60 sec RGB  (Total time: 90 minutes)    @ 300 Gain   50  Ofsett @ -20oC    



A 15 x 180sec Darks  20 x 1/4000 sec Bias  10 x Flats LRGB  @ ADU 25,000  

B 15 x 60sec Darks     20 x 1/4000 sec Bias  10 x Flats LRGB  @ ADU 25,000  

Location & Darkness Fairvale Observatory South – Redhill – Surrey – UK       Typically Bortle 5
Date & Time (A)    18th  &   (B) 19th May 2018 @ +23.45h approx.




Star Struck


M13 LRGB F2 CROP (Large)

Of all the things I’ve discovered since taking up astronomy, perhaps it is the presence and nature of globular clusters that has most surprised me. Bound closely together by gravity, these massive spherical collections of stars orbit the galactic core perpendicular to its plane.  In the case of the Milky Way there are 150 globular clusters but they can be much larger in other galaxies, such as M87 which has some 13,000; clusters of clusters have also now been discovered in the Universe!  Typically each cluster might contain a few thousand or tens of thousands of stars, although in some cases they can be much larger.  Omega Centauri is the largest globular cluster in the Milky Way, being 150 light-years in diameter it contains 10 million stars; though clearly visible from Earth it can only be viewed from the Southern Hemisphere, which we unfortunately did not see when in New Zealand earlier this year.

MW & globs

Despite all the advances being made in cosmology, the origin of globular clusters still seems to remain quite uncertain.  Characteristically the stars are all very old, typically in the region of 8 to 12-billion years and are of low metallicity i.e. they contain a low proportion of elements other than hydrogen and helium.  At least some, such as Alpha Centauri, are thought to have condensed from dwarf galaxies and such a process may currently be taking place within the large Magellanic Cloud – which we did see in New Zealand!  In other cases it is thought that the clusters have probably originated independently and were subsequently captured by the relevant galaxies.  However, their very old age – sometimes nearly as old as the universe itself – origin and relationship to galaxies remains intriguing.  For these and many other reasons I personally find globular clusters fascinating, probably more than any other astronomical feature, amazing as they too may be.


Globular Clusters May 2018: M3, M13 & M92 (red circles) + Others (yellow circles)

From time-to-time I’ve tried imaging various globular clusters but have not been satisfied with the outcome.  Now using guiding, plate solving and the high-resolution ZWO1600MM-Cool camera, it was time to give it another try this spring, when some of the best clusters are present in the northern night sky.

M3 LRGB Final (Large)

First up was M3 (Final image above), the very first Messier Object to be discovered by Charles Messier himself in 1764.  Consisting of 500,000 stars, between 8 and 11-billion years old and spanning some 220 light-years, M3 is one of the largest and brightest (absolute) globular clusters associated with the Milky Way – about 300,000 times brighter than our Sun.  It is noteworthy that the cluster contains some 274 variable stars, the highest number of any clusters, as well as a relatively high number of ‘blue stragglers’ – young main-sequence stars that appear to bluer and more luminous than the other stars in the cluster and are thought to be formed through stellar interaction of the older stars.

M3 LRGB Crop (Large)

With these attributes it is not surprising that M3 is considered a popular target in astrophotography (cropped image above), likely surpassed however by M13 AKA the Great Globular Cluster in Hercules (cropped image top-of-the-page), which conveniently follows M3 in the same area of the sky about 3-hours later (together with nearby the globular cluster M92).  And so having bagged M3 it was time to turn the telescope and camera towards M13 (Main image below).  Discovered by the eponymous Edmond Hailey in 1716 (he of Hailey’s Comet), seen from Earth M13 is slightly brighter than M3 with a wide range of star colours that certainly makes for an exciting image.  At 11.65 billion years old, M13 has been around almost three times as long as the planet Earth.

M13 LRGB Final (Large)

Since starting astrophotography I like to try my hand at imaging a globular cluster at least once each year but hitherto with disappointing results.  This time I’m pleased with the outcome, especially M13 which is surely one of the most magnificent objects in our night sky; as a bonus there are also a few galaxies in the background of both the M3 and M13 images too.  It is therefore fortunate that for those of us in the higher latitudes of the northern hemisphere the Great Globular Cluster in Hercules can be seen all-year round, though is at its highest and therefore best position between May and September – thereby inaccessible for the Kiwis who are instead compensated by Alpha Centauri!  I expect to be back again next year to marvel at these amazing and enigmatic objects, if not before.

M3 Location Crop

Object M3    (NGC 5272)     
Constellation Canes Venatici
Distance 33.9 million light-years
Size 18.0’ or 220 light-years     
Apparent Magnitude +6.2
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 ZWO x 8 + ZWO LRGB & Ha- OIII-SII 7nm filters 
Capture & Processing Astro Photography Tool + PS2,  Deep Sky Stacker & Photoshop CS2
Image Location Centre  RA 13:42:23     DEC 28:22:50  
Exposures 24 x 180 sec L + 10×180 sec RGB  (Total time: 162 minutes)   
  Unity @ 139 Gain   21  Offset @ -20oC    
Calibration 10 x 180sec Darks  20 x 1/4000 sec Bias  10 x Flats LRGB  @ ADU 25,000  
Location & Darkness Fairvale Observatory – Redhill – Surrey – UK        Typically Bortle 5
Date & Time 5th + 6th  May 2018 @ +23.00h

M13 Location Crop

Object M13     (NGC 6205)
Constellation Hercules
Distance >=20,000 light-years
Size 20’  or 150 light-years
Apparent Magnitude +5.8
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 + PS2,  Deep Sky Stacker & Photoshop CS2
Image Location Centre  RA 12:39:59    DEC -11:37:20  
Exposures 20 x 180 sec L + 15×180 sec RGB  (Total time: 195 minutes)   
  @ Unity 139 Gain   21  Offset @ -20oC  USB 40 
Calibration 10 x 180sec Darks  20 x 1/4000 sec Bias  10 x Flats LRGB  @ ADU 25,000  
Location & Darkness Fairvale Observatory – Redhill – Surrey – UK        Typically Bortle 5
Date & Time 6th + 7th + 9th May 2018 @ +00.30h  



LRGB GxC Crop-2 (Large)


I always had a general interest in astronomy but was eventually sparked into action after viewing Saturn through the Thompson 26 inch refractor at Herstmonceaux observatory in 2014.  The beauty of the planet and its unique rings is captivating and like many others it remains my favourite planet to this day.  One year on and looking further afield at Joan Genebriera’s Tacande Observatory on the island of La Palma, I discovered what is now  one of my very favourite Deep Sky Objects – M104 or the Sombrero Galaxy; until recently I used the resulting picture obtained whilst at La Palma as the main banner image for this website.  Though perhaps not as spectacular as the Orion Nebula or certain spiral galaxies, the sombrero-like galaxy (with a passing resemblance of a flying saucer too), is beguiling in its own unique way and ever since then I’ve been eager to return to The Hat and image it myself from home.


However, imaging the Sombrero from the UK and especially at my location just south of London is quite another matter to La Palma.  Aside from light pollution, being at 51o north compared to 28o in La Palma, M104 is considerably lower in the sky when viewed from Fairvale Observatory in Redhill; at the time of imaging in early May it was about 26o above the southern horizon.  Furthermore, my sight lines are obscured on three sides by 15-foot hedges and directly south by two 45-foot conifers – see below SE to SW view of M104 imaging track at Fairvale Observatory.

M104 Track crop

As a result, only after it emerges from behind the western edge of the aforesaid conifers can M104 (just) be imaged, as it moves along the top of the hedge for just over an hour before disappearing from view once again.  Of course this is far from ideal but with my enthusiasm for the Sombrero, a high-resolution ZWO1600M-Cool camera and newly acquired ability to plate solve, I gave it a try over three consecutive nights.


RGB GxC crop (Large)


An unbarred spiral galaxy, the hallmark of M104 is its bright bulbous centre encircled by dark dust lanes, which when viewed from Earth tilted at just 6-degrees above the equatorial plane creates the appearance of a sombrero hat (see cropped image above).  With the much higher resolution of the Hubble telescope some 2,000 globular clusters have been identified with M104, ten-times that of the Milky Way.  In 1912 the galaxy was found to be moving away from Earth at 700 miles per second, providing an early indication that the Universe was in fact expanding in all directions.

All-in-all the Sombrero galaxy is a fascinating and unusual object, though small and all-in-all a challenging imaging target, especially seen from Fairvale Observatory.  Notwithstanding, at last I am very pleased to obtain my own exciting image of the Sombrero – chapeau!

M104 Location

Object Sombrero Galaxy  M104     
Constellation Virgo
Distance 29 million light-years
Size 9’ x 4’  or  50,000 light-years
Apparent Magnitude +8.0
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 + PS2,  Deep Sky Stacker & Photoshop CS2
Image Position Centre  RA 12:39:59    DEC -11:37:20  
Exposures 25 x 180 sec L + 3x5x180 sec RGB  (Total time: 120 minutes)   
  @ 139 Gain   21  Offset @ -20oC    
Calibration 10 x 180sec Darks  20 x 1/4000 sec Bias  10 x Flats LRGB  @ ADU 25,000  
Location & Darkness Fairvale Observatory – Redhill – Surrey – UK        Typically Bortle 5
Date & Time 5h + 6th + 7th  May 2018 @ 23.30h  approx.



AstroBites-2: Home Sweet Home

IMG_8748 FINAL (Large)

From time-to-time I’ve been fortunate to see the Milky Way but due to the lack of dark skies, rarely in the UK.  With a move towards urbanisation taking place throughout the world, light pollution is a major obstacle to such views and astronomy in general and it is only in more remote, unpopulated locations that such sights are now possible.  On such occasions a view of our galaxy from within is always striking and usually memorable. I’ve been fortunate to visit many such remote places but either didn’t look upwards (why not?) or was hindered by the inevitable cloud.  Recently on a trip in 2016 to Arizona and Utah in the South West USA, such views were hampered by the full moon – timing is everything!  However, there have been two occasions when the darkness was so complete that I found the view of the Milky Way to be not only incredible but quiet profound – first in the Kalahari desert in Botswana and subsequently on a scuba diving trip whilst motoring southwards along the middle of the Red Sea at night with the boat’s lights turned off.

Notwithstanding, since my interest in astronomy started a few years ago I have yet to successfully image the Milky Way, which has remained resolutely elusive to my camera sensor.  I have tried a few times at Fairvale Observatory but the night sky here at best rates 5 on the Bortle scale and makes such imaging almost impossible.  Then whilst in the Arizona desert last year (see above) and on other occasions I have been thwarted by a full moon.  Apart from the obvious problem of light pollution I was beginning to wonder if I was doing something wrong but no, it was the sky conditions.

Finally during September this year, whilst camping in Dorset on the Isle of Purbeck just west of Corfe Castle, I at last managed to image the all elusive galaxy – our galaxy (see top of page).  Looking south across the Purbeck hills towards the English Channel, the Milky Way was revealed in all its glory traversing the clear, very dark sky which itself was pierced by the vivid light of the myriad of stars; it is on such occasions I realise just what I’m missing at home.  Once accustomed to the darkness the form and some detail of the Milky Way could be clearly discerned with the naked eye but of course the camera saw a lot more.

Picture saved with settings embedded.

Some processing shows good detail of the Milky Way but at ISO 6400 is too noisy

Using my unmodded Canon 700D DSLR and an ultra wide-angle 10mm lens, for the first time I was able to capture some reasonable images of the Milky Way.  All were shot on a static tripod between 15 and 20 second exposures at ISO 6,400; I had set-up the camera on the Vixen Polarie for tracking but could not obtain a favourable view of the galaxy in this way.  From this experience next time I would reduce the ISO to at least 3,200 or less and increase the exposure time based on the ‘Rule of 500’ to about 30 seconds.  However, for now I’m happy with the result and hope the next opportunity doesn’t take another  lifetime coming.

A New Palette


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 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.

IMG_20170328_085919971_HDR (Medium)

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.


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.

rgb2gx (Large)

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


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