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Category: Astrophotography

Base Camp 2 - A New Beginning

Astrophotography with the Sigma fp L – Having worked for a year with the SIGMA fp (see article (1) and article (2) here). It was always clear that the SIGMA fp L might be an extremely interesting alternative. As such I arranged for a SIGMA fp L to be de-bayered (via monochromeimaging – a considerably more challenging task than with the fp!)  The SIGMA fp L I have reviewed before (see here), and it offers considerably flexibility with respect to the fp for terrestrial photography. From an astrophotography perspective, there are compromises that have to be made for the extra resolution, that a 62MP monochrome camera brings.  The smaller pixels 3.78 µm vs 5.98 µm in the fp, means that the sensor is more prone to noise than the fp, albeit in a camera that, due to the presence of the heatsink, controls noise very well. As a result, the “sweet spot” for the ISO for the SIGMA fp L is ISO 400 whereas it is ISO 1250 for the fp. Having both cameras available means that for strong signals (very often the Ha signal in a nebula) I can call on the resolution of the SIGMA fp L, whereas for fainter signals and/or if time is short, I can fall back on the better signal to noise ratio of the fp.

As of June 2023, an ASCOM driver is now available for the SIGMA fp L. ASCOM drivers are the communication protocols for much astrophotography equipment, and this means that many aspects of our workflow with a SIGMA fp L can now be automated. Whilst the live view via the camera HDMI output in combination with SharpCap remains the ideal method to build the tracking model that the 10 Micron GM1000 HPS needs, connecting the camera to the computer via the USB-C port allows camera to be connected with a program such as N.I.N.A. and the focusing of the telescope can be automated. With a telescope (Celestron RASA 11” V2), where the focus is highly sensitive to temperature changes during the course of the night, this is a significant step forward.

Astrophotography begins at home ...

Out in the field, and this year (2023) for health reasons from home, the SIGMA fp L has not disappointed and I am extremely pleased with the data that I have been able to obtain with the camera. The Lion Nebula (Sh2-132) (extract as title image) and the Veil Nebula Complex “Detail” image (below) being a case in point.

Everything has now fallen into place: I feel that my choice of cameras for astrophotography has been vindicated; Workflows are well established and delivering the results, which match both our photographic and in particular our artistic expectations.  This we took as a decision point to relaunch our astrophotography work under the brand “Astrophotography.Art”. Whilst we remain active nature photographers, with our work being displayed at and, all of our astrophotography work will be found here on this website.  

We are very much looking forward to many long nights under a clear and starry sky. In terrestrial photography, it is customary to wish another photographer “Good Light”, wish us instead “Bad Light” and, of course, “Clear Skies” …

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Climbing The Learning Curve

Astrophotography with the SIGMA fp (2) – 6 Months into my astrophotography journey, I thought it would be good to take stock of lessons learned and the “state-of-play”. It’s been a great journey so far, with results with which I am really pleased. So, as I bring this first chapter to a close – I would like to detail some of the many aspects involved.

Locations: I made a very conscious decision at the beginning that I would always travel, every single full moon to ensure that I would have (as far that it is possible) somewhere in northwest Europe a clear sky when there would be a new moon. Ideally, this would also be in a “dark-sky” or at least considerably darker sky than where I live in Germany. I have used to Apps to guide me here “Windy” and “Light Pollution Map”. Windy is a phenomenal and, in my experience, an extremely accurate weather app, which allows me to track the development of weather systems across the whole of Europe. The light pollution map allows me to pinpoint locations which then have the darker skies. The combination has meant that I have always been able to find a location, though naturally the weather has meant that this is not always under the darkest sky. The final help comes from “Street View” within Google Earth. I am still amazed (as a pre-internet child) that I can accurately scout a location somewhere in the mountains in northwest Italy or northern Spain (so far 1800 km from where I live has been the remotest location) and identify, in advance, the exact spot where I should be able to set up my telescope and then to be able to drive to exactly this spot. Of course, it is not always so easy, and the vagaries of an unstable weather system have meant that plans have needed to change at short notice and sometimes, what seems like a good location can hold hidden challenges – The rice fields in the province of Vercelli, Italy in May seemed like an excellent “fall-back” location, not particularly dark but a good expansive view. However, the dark clouds rising from the waters at sunset and the accompanying audible hum, declared the error in this thinking – I have never seen so many mosquitos – I don’t know whether it is possible overdose on Autan, the anti-bite spray that by pure chance I had buried in the boot of the car. If you can, I did! It worked, I didn’t get bitten once, but I never expected that perhaps I would have problems shouting an object because of the mass of insects that could be in front of the glass.

Rice fields in the province of Vercelli, Italy

Other challenges, in the fields in middle of France in April for example, have included “Steven-King-like” episodes of fog: Here, half-seen “Wraiths” rising from the ground gave warning of the impending end to the photography. A look behind and the approaching wall of fog appears. At such times one thinks of the classic horror movies where some minor character (who you know some 10 minutes later into the film will die horribly) says something like “Don’t worry, it’s just a bit of fog …”, and then, the contrast begins to disappear from each subsequent exposure and you begin wiping the water off the computer screen, and you begin listening very intensively to every noise … Such events are however soon forgotten, as one stands in some remote range of hills and the beauty of the night sky appears, like an old friend, in all its majesty, out of the evening sky above and around you – and I am simply at awe

Parque Natural de la Serranía de Cuenca, Spain

Working with the telescope: The downside of working “on-the road” is that every single night the telescope and camera must be set-up from scratch and in the pre-dawn light dismantled again. Although both are now well-orchestrated events, it does mean that the first 60-90 minutes following the appearance of Polaris (first alignment check) are required to build the model for the sky that the tracker requires. With the long nights of February and March, this was not so noticeable, but when the astronomical night only last 4 hours (or less) in total then this adds a significant pressure to get everything right first time. Another reason to ”head south” in May and June, is that going from 50° to 40° latitude brings a good 60 or so minutes more “night”. The tracker model is (has to be) extremely accurate and even though the tripod is set up on kitchen tiles to spread the weight, on occasion the ground has proved to be less stable than anticipated with the very slight movements due to weight (ca. 50+ kg in total) being enough to ruin a night’s photography …

In the mountains north of La Spezia, Italy – Unfortunately, not as stable as I had hoped …

However, the most difficult task by far has been to focus the scope and I have progressed through many ways to achieve this. I really did not anticipate, although I knew in advance that a F2.2 Scope, such as the Celestron RASA 11”, is difficult to focus, indeed just how much work this would be. With over 40.000 single steps available to the focus motor (way more than could be achieved by hand), I did not anticipate that I would be able to see the difference in the fine structure of a nebula (when viewing conditions are good) between a single step of the focus motor, i.e. that say position 35.678 would be better than position 35.679 for example. Because light at different wavelengths has a different focus point (the basic physical property behind chromatic aberration in a terrestrial photographic lens), each narrowband filter has a different focus setting.

It is an “interesting” experience to be hunting for the final focus position for a new filter, when you are aware that only 45 minutes remains before the first signs of the pre-dawn light will appear … 😉 A good check has been to not focus on the potentially faint target at hand, but rather to pre-focus with the brightest nebulosity available (perhaps Orion in winter / Eagle in Summer) before moving to the desired target. It is a good that I enjoy a challenge. 😊

SIGMA fp (monochrome) with Pluto remote trigger and HDMI cable and telescope dew heater

Post processing: I always intended that I would work somewhat “unconventionally” with the data I would collect. Here, I really wanted to build on very many years of experience with post production of digital images. I am very pleased, that I have really been able to validate the assumptions I made as to why and how this should be possible. Of course, the first fundamental building block is that the camera has to deliver good data. Here, I have not been disappointed. The heatsink built into the camera to enable many hours of video shooting is just as effective with repeated long (5 minute) exposures during my astrophotography. I need to collect 3 types of data: “Flats”, “Dark” frames  and the “Lights” (the nebula data itself). The Flats I take about 1-2 hours before sunset (if there is no cloud) at around 60° inclination and in the opposite direction to the sun. This should be a uniformly exposed image, from which I will be able to correct vignetting in the “Lights” and be able to identify where any sensor spots may be present. The “Dark” frames, taken at the end of the evening by simply blocking the light entering the camera are used to generate a “Bad Pixel Map” and to identify any residual sensor noise not directly related to an image.  All these modifications are made to the individual “Lights”, which are processed (calibrated, registered, and integrated together) in Astro Pixel Processor (Mac only). The image data from each individual filter are then further processsed in Adobe Photoshop, where they are assigned to a colour channel or channels and these various colour channels are then blended to give a final (false colour) image. The choice of colour palette can have a dramatic effect on the final image and considerable creativity can be brought to play. By suitable choice of the colour channel(s) considerable detail can be made visible that would otherwise be lost.

It has been a wonderful journey so far and the idea of spending the next few nights under the clear skies of the next full moon somewhere in the middle of nowhere is as exciting as ever …

Clear Skies, Mark

Eagle Nebula / M16 / NGC 6611
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The Start Of The Journey

Astrophotography with the SIGMA fp I have always been fascinated by the night sky. In particular, the huge variety of Nebula and other Deep-Sky-Objects and the structures they contain. As such I have always had as a dream that one day, perhaps, I would be able to work with images of these objects myself. The launch of the SIGMA fp I took as the starting point for the journey to realise that dream.

Why the SIGMA fp ? This camera was designed as a stills and professional video camera. In order to be able to take video for several hours without overheating the camera has a heatsink built into it. This can be seen on the sides of the camera. This means that the camera is able to control digital noise extremely well. There is one other type of photography where this is absolutely critical and that is astro-photography. Faint Deep-Sky-Objects need very long exposure times at relatively high ISO values (most often around 1600 being a good compromise) and thus the control of digital noise is a fundamental factor towards producing a good image.  The “sweet-spot” for the SIGMA fp is ISO 1250.

SIGMA fp in place with the TC2011 2 x Converter and Baader Filter

My choice of telescope is the Celestron RASA 11” V2 (620mm, F2.2). Primarily driven by the desire to have as small an F-Stop as possible for the best possible light gathering properties. In the configuration of this telescope the camera sits in front of the glass (see image), which means that it is imperative that the camera is as small as possible. The SIGMA fp is the smallest full frame camera in the world – a perfect match.

With Pluto remote trigger and HDMI cable and telescope dew heater

As a tracker I have a 10Micron GM1000 HPS. This needs a model of the sky to be built by going to ca. 20 bright stars in turn and aligning these exactly. I have used the IOS 6 setting on the camera to block the light of all but the brightest stars making the model building significantly easier (plus 8x zoom in the camera live-view plus 9x zoom in the field monitor – HDMI feed).

All set and ready to go …

Its been a steep learning curve 😉 … From the first outings under an 85% moon (Rosetta/Orion/Horsehead Nebulas) and hard, high humidity frosts (Think – “The Day after Tomorrow” 😀 …) to every set-up and focussing error I can think of (and several I didn’t) … Focus is achieved using SharpCap, which takes the camera live-view feed after feeding through a field monitor, which is how I do most of my macro work, via a video capture card and the Celestron USB Focus-motor. This is probably the most difficult task and something that would be almost impossible to achieve without the focus motor and computational interpretation of the diameters of the stars. At 02:00 in the morning, sub zero temperatures, and already 6-8 hours “on the job”, keeping the mental discipline to get the focus right is not easy.

Since there are no “green” Deep-Sky-Objects, the green pixels (50% of all available pixels) in a full colour camera are very under utilised. The SIGMA fp I have, has thus been de-bayered (very many thanks to Daniel @ That means the blue/green/red sensor mask has been removed so that all the pixels can see all the colours (producing a monotone image). It now only has a glass screen that lets everything from UV to IR and have had a lot of fun using this as a terrestrial monochrome camera. Since I live in an area with relatively high levels of light pollution (Milky Way is rarely, if ever, visible to any extent), I need to work with “narrowband” filters. The images from these different filters are recombined to produce the full colour image. These narrowband filters are specifically tuned to only let through a single emission line: Hydrogen (H-alpha = 656nm), Sulfur (S-II = 672nm) and Oxygen (O-III = 501nm) so that much of the light pollution can be subdued. 

It has been a very interesting experience chasing the most boring landscapes and skies that I can imagine: Totally flat and no “red cloud” sunsets – A different kind of “Big Sky” 😀 (Even if I don’t want to shoot an object when it is low in the sky, the bigger the view the more stars that are available to build the tracking model).

No landscape photographers here ...

Everybody remember’s their “First-Time”: Well, I can tell you, after over 2 years of planning and research (and 9 months waiting for the GM1000), the first time I pointed the scope at “IC 434”, triggered the shutter for 30 seconds and saw on the field monitor the unmistakeable silhouette of the Horse’s Head appear (1240mm via the SIGMA TC2011 2x converter) – “YES!” – It was a pretty big smile! The data are not as good as they could be (85% Moon); the focus and/or seeing perhaps not quite as I would like; but I didn’t care – That is the moment and shot, I’ll always remember, and, I will be as proud of this shot as any other that I will ever take …

Horsehead Nebula / Barnard 33

Its been an interesting few weeks and I have have really enjoyed the start of the journey! The SIGMA fp in combination with the Celestron RASA 11″ and the 10Micron GM1000 HPS has shown that it can produce the results I was hoping for … I am very much looking forward to the next New Moon 🙂

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