The Big Picture

I’ve been very happy with my main imaging set-up for nearly 4-years: Skywatcher AZ-EQ6 GT Mount + William Optics GT81 + ZWO1600MM-Cool mono camera.  Nevertheless, thoughts inevitably stray towards the big and usually expensive question – what next?  Given the said equipment, a natural move is likely to be the addition of a larger telescope to get at those faint fuzzies and I have been toying with such an idea for some time – probably another refractor in the 100mm to 130mm range.  However, I’ve always been held back by a number of nagging issues:

• Without a sightline of Polaris for polar alignment from the main location at Fairvale Observatory,  guiding is always going to be sub-optimal – I can get away with it with the smaller William Optics but a larger aperture / focal length would be more challenging;
• Being a set-up / take-down observatory each night, the increased technical demands of a larger OTA would certainly take longer and in general be more difficult to undertake – as I get older moving the mount is already taking its toll on my back;
• Time is short as there’s simply no getting away from the problem we all suffer in the UK – cloud and lots of it!  It’s been normal to go weeks, even months without a clear night sky and as a result last year I managed to image just 18 objects over some 27 nights, of which some were only over a few hours before the clouds rolled in;
• A static observatory would help enormously but my garden is unsuitable: apart from the aforesaid problem that my house obscures a northerly view, there are also houses and substantial trees and very high hedges on all the other sides.

Regretfully I have therefore always come to the same conclusion, that unless I moved house it was best to continue with my current set-up – until now!  Inspired by a fascinating thread on the Stargazers Lounge Forum the solution was blindingly obvious, or at least it was once I understood there was another way, a larger field-of-view rather than larger telescope, achieved with a traditional though far from ordinary camera lens.

As a life-long photographer on land and underwater, astrophotography surprisingly came as something of a shock, as it’s just so contrasting to the aforesaid disciplines and requires quite different technical knowledge and aptitude.  Of course, I’ve often used my camera equipment to image the night sky, particularly the Milky Way and started out astrophotography using a modded DSLR but otherwise did not consider that a camera lens could form the basis for my astrophotography going forwards – then I discovered the Samyang 135 f2 lens.  Moreover, looking at what others achieved matching this lens with a tracking mount and mono camera, the decision to join the Samy club was a no brainer.

Located in South Korea, Samyang Optics has been manufacturing good camera lenses since 1972.  Also sold under the Rokinon brand name, the Samyang 135 f2 stands out for two reasons:

1. The optics of the lens are top drawer, consisting of 11-elements in 7-groups using very high quality glass;
2. The lens is very well suited to gathering photons with a maximum f2 aperture – though most users stop down to 2.8 in order to achieve good star shapes right into the corners.

The optical quality produces sharp image quality from corner to corner but combining this with a 135mm focal length achieves an enormous 9.45^o x 6.30^o field of view @ f2 with a Canon 550D compared with my current set-up of 2.67^o x 1.78^o, opening up whole new imaging possibilities.

Inner rectangle: FOV using William Optics GT81 + focal reducer & ZWO 1600MM-Cool camera
Outer rectangle: FOV using Samyang 135 f/2 & CAnon 550D DSLR camera
It would take approximately a 9 x panel mosaic from the WO to cover the Samyang area!

Furthermore, this much smaller rig is lighter, easier and thus quicker to set-up and break-down.  Put together it’s a powerful combination that I hope to fully exploit in the future.

Camera	Equipment	FOV	Resolution
ZWO ASI1600MM-Cool	WO GT81 + 0.80 FR*	2.65o x 2.00o	2.05”/px
	Samyang 135 f/2	7.50o x 5.67o	5.80”/px
Canon 550D DSLR	WO GT81 + 0/80 FR*	2.67o x 1.78o	1.85”/px
	Samyang 135 f/2	9.45o x 6.30o	6.45”/px

*Current set-up  

By today’s standards this lens might be considered somewhat old fashioned with no autofocus or image stabilisation etc., but the intrinsic high manufacturing standards and manual focus are excellent for those who know how to handle such a lens and perfect for astrophotography.  For such a purpose users generally either create their own rig by adapting various astronomy bits and pieces or use one of a growing number of bespoke brackets that are being made for this increasingly popular lens.

For the moment I chose to use a 3D printed bracket and integrated manual microfocuser, made by the French company AstroKraken and its founder Philippe Leca.  Therein the lens is cradled by two hinged rings, which when screwed down hold the lens firmly to either a Vixen bar or Losmandy plate.  The microfocuser then fits snuggly around and then clamps onto the focus ring, so that two screws on either side can be adjusted so as to push against a bridge located above and between the two rings, thus providing fine control over the focus ring; the said bridge also has a Synta fitting shoe on top to fix a finder / guide scope.  Altogether it’s a neat and very effective design that provides an easy-to-use tailor made platform for the lens, which can then be combined either with a DSLR or mono camera on the back; users of mono cameras tend to recommend changing the lens’ bayonet for a screw fitting and possibly add a third ring for the camera in order to eliminate the possibility of any flexure.

Whilst the AstroKraken bracket works well, the structural layout is inevitably tight making it difficult to view the focus ring settings but once established close to focus, subsequent use of the microfocuser is excellent in finessing the job of focussing before locking down the adjustment screws.  In addition, I’ve acquired a second Starlight Express Lodestar X2 autoguiding camera for use with a Skywatcher Evoguide 50ED guidescope but so far have not needed it with short exposures currently being used.

As a project for the new rig I had intended to spend the late summer imaging the suitably large Cygnus HII region but in the end conditions limited my time on this wonderful area of the sky at this time of the year and will have to wait for another time.  Notwithstanding, first light using my modded Canon 550D DSLR camera of the said Cygnus area was briefly achieved at the end of July, with promising results (see above – uncropped).  More recently, in early September I was able to obtain images of the Veil Nebula (see below – cropped to 70%) and North America Nebula (see top-of-the page, cropped to 80%), in all cases taken at 120sec exposures and ISO 1600.  Unfortunately all integration times have been just under 60 minutes for each target and in the long run the real magic of this lens will be unlocked with the addition of a mono camera and much greater imaging times.

Looking back personally and professionally, it’s apparent to me that the concept of the big picture, metaphorically or otherwise, has played a central role in my life and is an area I like to work with; it’s the big picture that provides context, understanding and opportunity. Perhaps it should therefore not be a surprise that in the end my next step in astrophotography will now follow such a path.  The detail provided with my current equipment is fulfilling and beautiful but the additional context provided by the Samyang’s extensive FOV can be more insightful and even breathtaking in scope.  After something of a slow start, I’m now really looking forwards to spending more time with this new and exciting rig in the future.