Shooting Comet Leonard in Ireland in Dec 2021

February 17, 2022  •  Leave a Comment

I was thrilled to see my four-shot composite of Comet Leonard in the January 2022 issue of Astronomy Ireland magazine – and even happier when I was asked to write an article about how I got it for the following month’s issue. In the article, I promised a longer version here on my blog and this is it – albeit a bit later than intended!

My article in the February 2022 issue of Astronomy Ireland.

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It was my second comet shoot, following Neowise over Lough Ree on the River Shannon in 2020 Comet Neowise by John Coveney. I’ll do a follow up blog about that in a few weeks time – and I’ll also include previously unpublished shots of Neowise over Dublin landmarks.

Comet Leonard was much dimmer than Neowise, at least when it was visible from Ireland, so I wasn’t sure if I could get it at all, much less get a good picture. I’ve been an active photographer for over 20 years now, starting with birds and then expanding to people, places and wildlife. One of my regular “places” over the last decade, or so, is my long-term lunatic project  around Dublin Bay the City Centre Irish Moonscapes. For this, I usually shoot the Moon in a land or sea context. So, I’m really chancing my arm at this astrophotography lark - ahem 😊. Other than my long lenses, I don’t have any specialist gear such as a star tracker or a lens warmer  lens warmer.   .  .   yet! So, this blog post is definitely not a guide to astrophotography. It’s more a journal of my intermittent meandering into this nocturnal imaging niche.

Since I started actual astrophotography a few years ago, mainly of planets and comets so far, I’ve used Stellarium’s free planetarium software. I use the computer version on a large screen at home for planning. But the Stellarium programme doesn’t automatically show comets – they have to be added manually via a deep dive into obscure settings. Fortunately, this blog How to Add a Comet to Stellarium by an American nature photographer, Martin Belan, clearly lists the sequence of simple steps required to add a comet  – it’s one of several similar links on Google.

Stellarium screenshot showing the complicated comet addition menus  .   .   . unless you follow Martin Belan’s guide .

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On location, I use Stellarium’s phone app to confirm object positions in the sky and to slowly build my familiarity with the heavens. When using the Stellarium app at night, the first thing is to press the Six Squares menu icon at the bottom left to show the Eye button. Use this to turn on and off Stellarium’s red filter to protect your night vision. It takes at least thirty minutes for your eyes to become fully dark adapted  – and longer for older people. However, a glance at a bright phone screen will quickly degrade your night vision. Unfortunately Stellarium’s red filter only works when you are using the app, so I also use a free android app, Twilight,  from the Google Play Store. This applies a reddish filter to the whole phone screen in every app so I can use other apps such as Google Maps or Photopills – but  not, of course, do any mindless social media scrolling during the darkest hours 😊.  And of course, for safety reasons, I never publicly post my shoot locations in advance!

This reddish filter is not great but it’s better than nothing and I also turn down the screen brightness. This also helps save the phone’s battery, especially if it’s cold. Of course I also have a head torch with a separate red light for protecting my night vision, as well as a battery pack to keep the torch and phone charged. It’s often said you should be able to use you camera in the dark, but that won’t help you find your way home across dark unfamiliar terrain after a shoot – been there, done that – and once was quite enough!

Stellarium app screenshot showing the Six Squares menu icon (left) and the Sensor Mode and red filter Eye icons (right) 

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The Sensor Mode tool in the phone app – accessed via the shaking phone symbol - is also very handy. Just point your phone up in the general direction of the object you are looking for and Stellarium automatically shows a zoomable image of the sky in that direction. Sometimes though, you might want to turn off Sensor Mode to stop the image of the sky jumping around as you move your phone, especially if you’ve zoomed in. You’ll also want to turn off the Sensor Mode if you just want to familiarise yourself with the stars in a patch of sky, perhaps while you are looking at the phone in your lap. I believe the phone app can also show comets, but I don’t yet know how to make this work – nor can I find a link on Google. If you know, please tell me in the comments.

You’ll also need to  ensure your phone’s compass is calibrated – and it’s best to do this in advance of a shoot. If you don’t, the Stellarium phone app may appear to be “looking” in the wrong direction in Sensor Mode. Firstly, you’ll need to be outside to get a good GPS signal. On an android phone, press the My Location circle near the bottom right of the Google Maps screen, and then zoom in on the blue circle that shows where you are – and expand it. Then lightly top on this blue circle to bring up the Your Location menu – don’t press too hard or you’ll drop a pin instead. Finally press the Calibrate button – depending on your location it will give you options such as moving your phone in a figure eight or taking pictures of a shop front. I think the figure eight option is more likely if you are in a rural dark location doing astrophotography. This is as much as I’m going to do on compass calibration and location accuracy in this post so, if you want more for android phones or any information on this topic for iPhones, you’ll need to Google it, sorry. If you have suggestions for either operating system, please add them in  the comments.

Anyway, as I scrolled through time on Stellarium on my computer last November, watching Leonard move in front of the stars, I thought of trying a composite to show this in reality.

Screen capture video of Stellarium showing Comet Leonard moving across the sky at the time of my Shanganagh Park shoot. Note d Boo near the bottom and the HIP 68785 “double” star at the top right (the dimmer nearby third orange star shown by Stellarium didn’t show in my shots). Note that using the Equatorial Mount option in the Stellarium programme to keep the stars relatively fixed as Leonard moved, tilted the orientation rightwards compared to my own images below. Once this is taken into account though, this simulation matches my images.

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Given Irish December weather, a multi-night series wasn’t on. However, the forecast for December 5th 2021 was cold and clear, but breezy. So about 1am and dressed in all my layers, I packed up my ebike for a short cycle to a nearby fairly dark area in my local park. This is Shanganagh Park – between Bray & my adopted home village of Shankill. It’s near the southern boundary of Co. Dublin. The Park is in a narrow greenbelt between Shankill and Co. Wicklow. In the strong westerly breeze, I sheltered on the eastern side of a patch of planted woodland just above the cliffs overlooking the Irish Sea

Maps showing the location of Dublin on the east coast of Ireland (top right), Shankill (left), my darkish shoot location sheltered by trees in Shanganagh Park (centre), and lastly the location of the Cooley Peninsular for my second Leonard shoot.

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My comet shoot station in Shanganagh Park – with Killiney Hill in the background. The streetlights there, over 4km distant, were the only ones I could see during the shoot. Note the foam garden kneeler for keeping my bum warm and, on the right,  the 400 2.8  lens lit by the red bulb of my headtorch.

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Stellarium said to look for Comet Leonard above Arcturus – rising about 2am in the northeast. Arcturus is in the constellation Boötes – the ploughman of the Plough according to the ancient Greeks. Arcturus is the brightest star in the northern sky and located in the groin area of Bootes, heavenly humour from an ancient - and presumably male - astronomer, perhaps?

Screenshots from Stellarium showing constellations around Comet Leonard during the shoot.

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I thought I could see Leonard with my binoculars but I wasn’t sure, so I did “search shots” with my Canon 85mm f1.8 lens – set at ISO 3200 for 5 seconds to get as much light as possible. About 2.50am, I was delighted to see Leonard as a small greyish blur on the camera’s LCD – as in the next illustration

Uncropped unprocessed 85mm image of Comet Leonard between the HIP 68785 “double” star and d Boo, as well as two satellite trails with square ends (Canon 80D and 85mm f1.8 at f1.8 for 3.2 seconds at ISO 3200). Two bright stars in Bootes, Arcturus and Muphrid, are also marked. The curved line shows a roughly U shaped group of stars, one of the star patterns I used to “crab” my 400 f1.8 lens from Arcturus to Leonard. The inset shows a processed crop of this shot around the comet.

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Once I knew I had Leonard, I reduced the exposure time to 3.2 seconds to reduce star trails using the Spot Stars feature on the PhotoPills app on my phone. This was a compromise between the 4 seconds given for the traditional 500 Rule and PhotoPills recommended 2 seconds. I kept shooting every half-hour or so, until the start of astronomical twilight at 6.30am – in retrospect I could probably have kept going until the start of nautical twilight about 7am. During my shoot, Leonard travelled about 925,000km at 70km/sec - about 2.5 times the distance to the Moon!

In between, I tried to set up my recently purchased second-hand super-telephoto – a 400mm f2.8 Mk1 IS – it weighs 5.4kg or almost 12lbs! I picked it up second-hand in Conn’s cameras in Dublin a little over a year ago. It was on their used equipment page - for many many thousands of euro less than their asking price for the current Mk3/RF versions at about  €14,000. These current versions are only a little more than half as heavy as my Mk1. I was sure the Mk1 would be a very well used or even battered pro sports photographer’s specimen, but when I next ventured into Conns – always a dangerous experience as they always end up richer! – I couldn’t resist asking for a look. To my astonishment it was almost pristine. Apparently it had been almost unused for up to 20 years or so since this model  first appeared in in 1999 . The reason it was so (relatively) cheap was because Canon no longer supplies parts for it. Anyway after getting it checked out by Eoghan Murray of f1 camera repair in Greystones in Co. Wicklow, I took a chance on it. With quite a lot of padding, it even fits in one of my ebike panniers.

So what was it like for astrophotography? Until or if I get a high spec star tracker capable of taking its weight and I can try it on a few deep space objects such as star clusters or galaxies, it’s too soon to say definitively. I would have loved to have tried it on Leonard as it passed the M3 star cluster  two days earlier but it was cloudy in Ireland that night – what a surprise! Without a star tracker and/or GoTo mount, I had to painfully “crab” from Arcturus to Leonard, taking a test shot each time and checking star patterns on the LCD against the Stellarium app. And now after all the long scéal (story in Irish), here’s my best image – the settings were 1.6 seconds, f2.8 (of course!) and ISO 12,800. It’s notably better than the 85mm images, especially in capturing the comet’s green tone, but not so much that I wouldn’t be too upset if I had to travel light with just the 85mm lens and its one and one third of a stop wider aperture. The higher ISO due to the narrower aperture didn’t make sensor noise much worse. Again there are short star trails because I exposed for 1.6 seconds, instead of PhotoPills recommended 0.7 seconds.

Comet Leonard above d Boo – the brightest star at the bottom – taken with a Canon 80D and a Canon 400mm f2.8 for 1.6 seconds and ISO 12,800. Moderately cropped and processed in Lightroom.

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In the few days after the shoot, I used Lightroom to reduce digital noise, to eliminate reds and oranges from light pollution, and to enhance Leonard’s natural green colour. The final step was a “lighten blend” composite of the four best 85mm shots in Photoshop. As I didn’t get the stars to line up exactly, I masked the stars out in all but the top layer and I just let the different exposures of Leonard shine through from the lower layers.

Because of these small miss-alignments, my image is not quite an astronomically accurate representation of Leonard’s movement against the background stars. Despite this, it’s plenty good enough for me to tell the story of Leonard’s appearance in Irish skies. It’s a memory that will stay with me for the rest of my days  .   .   . and nights! This is just as well because it’s now leaving us forever! Like many comets, it is believed to have come from the hypothetical Oort Cloud of icy objects surrounding the Sun between 2,000 and 200,000 times the Sun-Earth distance. The Oort Cloud is hypothetical because objects in it are too small, dark and distant for even the largest telescopes to see from the Earth but it’s believed to be the source of many comets. Leonard had an orbital period of about 80,000 years, spanning about 3,500 times the distance between the Earth and the Sun. On this spin around the Sun however, it got a solar gravitational boost that will kick it out of the Solar System - to roam the depths of interstellar space.

Final four exposure composite of Comet Leonard over Shanganagh Park Co. Dublin on 5 December between 2.50 and 6.30am. HIP 68785 is the “double” star above and to the right while d Boo is the brightest star toward the bottom.

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Before I finish though, my Shanganagh Park shoot was not my only sighting of Leonard. Five days later, myself and herself had shnaked off for a couple days on our own to a nice B&B in Carlingford on the Cooley peninsula. Perhaps missing the central point of those few days 😊, I was out at Ballaghan Point just after 7am on the 10th of December. Although nautical twilight had begun, hence the blue background, I still got a shot of Leonard – and a meteor passing close by. Unlike the satellites in my shot above, this streak of light has a tapered end typical of a meteor as it burns up in the atmosphere.  Perhaps, it was a late Leonid wishing Leonard farewell as it began its eternal interstellar journey!

Comet Leonard and a meteor from Ballaghan Point on the Cooley Peninsula in Co. Louth taken at 7.05am – the start of nautical twilight – on 10 December 2021 with a Canon 80D and 85mm f1.8 for 3.2 seconds at ISO 3200.

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