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Comet C/2020 F3 (NEOWISE), 06-30 July 2020

After initially showing a lot of promise, the recent comets C/2019 Y4 (ATLAS) and C/2020 F8 (SWAN) both fizzled out, the former disintegrating and the latter failing to become impressive.

So, on to the next promising candidate: C/2020 F3 (NEOWISE). The comet was discovered on 27 March 2020 by the Near Earth Object instrument of NASA’s Wide-field Infrared Survey Explorer telescope (NEOWISE), passed through the field of view of the coronagraph of NASA's Solar and Heliospheric Observatory (SOHO) during 23-27 June and reached perihelion on 03 July 2020. It emerged from perihelion in early July, moving on a path through Auriga, Lynx and Ursa Major, well placed for observation from the northern hemisphere.

Nigel Evans, 30 July 2020

On 30 July, although a clear night was forecast, with the comet now a binocular object, I observed from my front garden and did not drive out to the countryside. I used a laser pointer to indicate its position to my neighbour. The photo below shows both tails of the comet.

I don't intend to record the comet any more.



Nigel Evans, 28 July 2020

On 28 July, from my usual observing site the comet would appear above a road. So I chose a convenient new site with a low northern horizon. This turned out to be a big mistake! The new site was OK until the outdoor security lights of a nearby building came on - I was never in the dark!

Fortunately, I brought a finder chart with me. Indeed, I would not have found the comet without it. The comet was a binocular object, appearing as a faint blob with a hint of a tail. I used long lenses, aiming to show the motion of the comet against the stars, rather than the extent of the tail as I have done in recent days. The following video, taken with a 300 mm lens, shows the comet drifting through the stars, then the stars drifting behind the comet. A single still frame shows little detail in the tail, so each video frame is a composite of five stills, in order to show detail in the dust tail. The ion tail is not visible.


Below, the still image taken with the same lens shows that the tails are now faint. Any background subtraction routine starts to remove the tail as well as the true background!


The following video and still are taken with a 100 mm lens rather than 300 mm. The video is similar to the above, but presents a wider field of view. Again, each frame is a composite of five stills. There is a hint of the blue ion tail, but only if you know where to look! The still below the video has a wider field of view than the above still, but shows the two distinct tails more clearly.



The following image is from a Canon 60Da camera on a static tripod. I have de-rotated the sky. The dust tail is visible for some 3°.


I recall a rule, from the old days of film, concerning the length of exposure of the night sky before trailing of the stars becomes noticeable. I knew it as the "500 rule", whereby the focal length in mm multiplied by the exposure time in seconds needed to be at most 500: thus a 50 mm lens with a 10 s exposure would be on the limit of acceptability. The rule was for equatorial regions of the sky and exposure times could be extended for polar regions. Some folk used a variant, the "700 rule". I found that 10 s exposures with a 35 mm lens exhibited significant trailing, so perhaps for digital photography, the "200 rule" or similar is required.


Martin Cook, 25 July 2020

Late at night, I was awoken from my slumbers by my wife with a faint call of my name, a prod in my side and a comment: "It’s clear outside."

I looked at the clock: it was 22:30 UT (11:30pm) and, looking out of the window, oh my! yes it was clear.

I went downstairs, grabbed a pair of 10x50 binoculars, carefully opened the patio door and proceeded down the garden only to be blinded by the security light! On recovering dark adaptation, I found that the comet wasn’t visible to the naked eye but could be seen in the binoculars low down in the north-west. I quickly set up my Skywatcher 200P, attached a Canon 1100D camera and then pointed the telescope towards the comet. I eventually found the comet in the finder scope but it appeared far fainter than during my previous observation (19 July, below) with only the head visible against the glow of the street lights.

As the night wore on and the comet drifted lower in the sky, the tail became increasingly indistinct due to atmospheric haze and light pollution. The following image was the best of a bad bunch.

Image details: 23:17 UT, Skywatcher 200P, Canon 1100d camera, 15 s exposure at ISO 800.



Nigel Evans, 22 July 2020

The night of 22 July offered the prospect of a clear sky, so out of town I went. It was the same as the previous evening: clouds all around the horizon and one sitting over Ursa Major and Ursa Minor. But tonight there was a bit of a breeze, so condensation would not be a issue. Cameras and tripods came out. While I was doing this a car came and stopped next to mine.

"Are you looking for the comet? Do you know where it is?" the driver asked.

Of course I said, "Yes, it's over there," pointing in the dark!

At the time the sky was not quite dark enough and NEOWISE was hiding behind a small thin cloud. But within five minutes I was able to describe where it was.

"Take the lower right star in the Plough. Come down to the horizon about halfway and you should see two stars at an angle. Look more closely [in binoculars] and you should see a third thing just above them. That's the comet!"

"OOOHH YES!" he replied.

He had been following pictures of the comet on NASA's Astronomy Picture Of the Day and wanted to see it himself. He realised that the photos showed far more than he would ever see, but he went away very happy.

Not 10 minutes after he left another car pulled up. Out popped a man and his daughter who had damaged her ankle and was walking with crutches.

"Are you photographing the comet?" he asked.

I was able to show them the comet. He revealed that he had seen Comet Bennett (in 1970) when he was a young boy at school.

So do I look like an astronomer, even in the dark? On my next outing, I think I will pack a laser pointer!

After an hour or so, clouds started to approach from the west, so it was time to stop my observations.

As for my site out-of-town, its chief redeeming feature is its low northern horizon. It is not a dark site. An idea of what can be achieved from a dark site in the UK is shown here. Damian Peach drove to Devon, with a view across water, specifically to capture this image!

So what of my images? I used one static and two driven cameras. Below, a video from the static camera gives a good overview of conditions: clouds around the horizon. The clouds did not seem to come from anywhere and go anywhere, but to appear and disappear in the sky before me. But they held back for a sufficient time for me to record the comet.


I also de-rotated and then stacked a set of stills to produce a pleasing image of the comet against Ursa Major. The image below is cropped, as the de-rotation of a view from a fish-eye lens is rather ugly around the edges.


The following video was taken by a driven Sony A7S with 100 mm lens. It comprises frames directly from the camera, without the usual processing. Apart from revealing that the polar alignment was not perfect, it provides a "true colour" picture, showing that the head of the comet is green.


To provide more detail in the tail, images need to be stacked. In the following video, each frame comprises five stacked (still) images. It first shows the comet moving among the stars, then the stars sliding behind the comet.


In the following video, each frame comprises 15 stacked images. This makes for a very short video, so it is looped a few times. I think structure, changing with time, is visible in the ion tail. The effect would be clearer with a longer lens, but I wanted to capture the whole tail.


In the following still, the tail of the comet extends as far as Phecda, more than 16° distant.


The second driven camera, another Sony A7S, carried a 50 mm lens specifically to catch the extent of the ion tail. I could create a video from the images it took, but it would resemble the above videos taken with a 100 mm lens but at half the scale. Alternatively, creating a stack of images would encounter the problem that the background is changing with time. The following image is a compromise; it is a stack of only 50 frames. Stacking more frames doesn't reveal a greater extent of the tail, not beyond the length shown above by the 100 mm lens, and makes the stars appear more streaky.


However if only the blue layer is selected from a larger stack of 219 images, the ion tail appears to extend beyond Phecda (perhaps with a little imagination!) The ion tail would have been more obvious from a dark site.



Nigel Evans, 21 July 2020

The biggest challenge in photographing the comet is that the sky over Suffolk is not dark. The field of view required to capture the entire comet is so large that the sky background varies in strength and in colour across a frame. It also varies with time, although I restricted exposures to only 10 or 15 seconds to minimise this. The forecast for the night of 21 July was uncertain, so I set off north of Ipswich to my customary observing site which offers a low northern horizon. As I left, there was some cloud in the direction of the comet; this, plus the uncertainty of the forecast, meant that I was not tempted to travel further afield for a site with a darker sky. On arriving at site, the entire horizon was full of cloud but, fortunately, the cloud covering Ursa Major and Polaris dispersed, and I set up two driven cameras to record the comet, and a fixed camera to record the general scene.

As time passed, the comet became ever lower in the sky, and I intended to end my observations when the traverse of the Astrotrak completed, after about two hours. However I checked the car windscreen and it felt damp: condensation was forming. It might not be long before condensation formed on the camera lenses too, even though all had lens hoods which would delay their cooling. I also had a look at Jupiter in binoculars - it was surrounded by a misty halo - time to call it a day. Indeed, there was a cloud bank advancing from the west that would anyway soon prevent further observations. My images from the night are below.

The following image shows the comet through the lower reaches of Ursa Major, the blue ion tail stretching at least as far as Merak (β UMa), some 13° distant from the coma.


The following video is a 1620x1080 px view (cropped from the much larger field of view of the camera), aligned first on the stars, then on the comet. Each frame is actually a sum of five subframes, in an attempt to bring out more detail in the tail.


Below is another video with a lens of even shorter focal length, namely 50 mm. Each frame is a sum of nine subframes. The video shows a short clip following the comet, then an inverted and slightly stretched version. In the latter, one can imagine that the tail might extend as far as Phecda (γ UMa) or Megrez (δ UMa), some 19° and 22° distant from the coma respectively.


In the following still from the Sony A7S, a similar degree of imagination is required when considering the extent of the tail.


The following image is the blue layer of the above, inverted and stretched, showing that the tail does indeed extend to Megrez.


The following video is a fish-eye view, taken with a static camera, of the general scene on site. On the horizon is the threat of cloud which, together with the imminent threat of condensation, eventually did force an end to the session. The video also captures the occasional headlights of passing cars.


Normally a static camera generates either a movie like the above, or star-trails. I tried something slightly different. I de-rotated 50 frames, then aligned them on the comet and summed them. The result is below. I haven't remove the gradients from the image. It shows magnitude 8 stars in Ursa Mayor and the blue ion tail of the comet, albeit only 2° or so in extent.



Nigel Evans, 20 July 2020

The weather for the evening of 20 July was forecast to be partly cloudy, and partly cloudy indeed it was. I was able to record a few images from a site north of Ipswich before a bank of cloud hid the comet. Bands of cloud moved slowly overhead and at times there seemed to be two sets of clouds moving in different directions! I promised myself that if the comet did not reappear before midnight, I would pack up and go home. Between gaps in the cloud overhead, the sky was actually quite clear. Finally a gap appeared in the clouds revealing the comet and the sky above it; alas it was merely the gap between two bands of clouds.

The image below has an uneven background: I think some high cirrus cloud was responsible for this. The camera is in portrait orientation (the zenith is to the right of the image) and the yellow colouration on the left is approaching cloud. The distance between the comet and Merak in Ursa Major is some 15°, and the ion tail just about reaches the star. I was surprised to record it to such an extent, given the conditions.



Roy Gooding, 20 July 2020

Image taken at 00:08 UT with a Nikon D5000 on a Sky-Watcher Star Adventurer driven mount. 18-55 mm lens, f4.5, ISO 2000.



James Appleton, 20 July 2020

I finally got around to trying to photograph the comet on 20 July. To avoid the light pollution from Ipswich, I travelled to a little-used lane north of the town, near Great Bealings, having reconnoitred possible observing locations earlier in the day. The site was perfect, and had the advantage of providing visibility of the red aircraft warning lights on the TV transmitter mast at Brockford, some 20 km distant, which provided a very effective and accurate means to set my camera lens to infinity focus!

20:55 UT. Arrived on site. The weather forecast for the evening had been perfect, predicting clear skies and good visibility all night. Alas, on arrival at site, it was immediately apparent that the forecast would be a triumph of optimism over reality as there was considerable scattered cloud, some of it dense, together with lots of haze making the sky appear "milky" in places. Jupiter, Saturn and Antares were prominent to the south, but no stars were visible to the north.

21:10 UT. First star becomes visible to the north: Capella, magnitude 0.1.

21:30 UT. The cloud to the north has largely dispersed and I spotted C2020F3 in binoculars, just as the ISS was passing overhead. I photographed the comet through thin cloud. Largely due to the cloud, the comet was invisible to the naked eye.

21:50 UT. I could discern the comet with the naked eye. Once found, I could see it with the naked eye thereafter, except when the cloud cover was particularly dense.

22:00 UT. Dense cloud has arrived in the north and obscured the comet. While waiting for the clouds to clear, I became aware of how noisy it was, with the odd train thundering by on the route to Lowestoft and the constant roar of the nearby A12, punctuated by the occasional high-revving din of a motorcycle engine being pushed to the limit by a motorcyclist attempting to break the land-speed record. Noise reached its peak as a pair of helicopters, presumed to be military, flew together slowly from south-west to north at low altitude.

22:40 UT. Clouds beginning to disperse to the north and the comet was visible again. I took some more photos.

22:50 UT. I noticed, out of the corner of my eye, a meteor in Cassiopeia. Unfortunately, there is no verification of this as my own meteor camera was not running and Alan Smith's was clouded out at the time!

23:00 UT. There remained much cloud to the north, so I packed up and headed home. The following morning, consulting the images from my meteor camera, it appeared that the cloud did not clear until circa 01:20 UT.

Unfortunately, all my photos were spoiled by cloud. Below is the best from a bad bunch! Taken at 22:44 UT, Canon 6D MkII with 24-105 mm lens at 105 mm, f5.6, ISO 10000.



Olaf Kirchner, 19 July 2020

Images of the comet taken from Genolier in Switzerland using a Canon 60D camera.




Martin Cook, 19 July 2020

On 19 July, the comet was visible low down from my back garden so I took the opportunity to photograph it with my Skywatcher 200P and Canon 1100D. The image below, taken at 22:07:40 UT, is a 10 s exposure at ISO 800. It shows a satellite streaking in front of the comet's tail, revealling its presence by a faint trail with a bright central flare (and another flare to the top left of the image). The satellite trail is caused by sunlight reflected from the object, and the flares are caused when a particularly reflective piece of the structure, such as a solar panel, comes into alignment with the observer.



Nigel Evans, 17 July 2020

The best viewing opportunity for the comet is now in the evening sky. The evening of 17 July offered moderate weather prospects, although with much wispy, hazy cloud. I was able to unpack everything quickly at 21:00 UT as there was still sufficient light. Clouds were present but did not look like a threat. However as the sky darkened new clouds formed and, just after 23:00 UT, the whole sky was blanketed with low fast-moving clouds from the east. It looked as if there was a ready supply of more so I packed up. By the time I had returned home the sky had cleared but I called it a night.

The following video was taken with my Brinno TLC 200 Pro. (At home, it would have been dazzled by the street lights that would still be on.) It made a change to see this camera show the comet appear out of the evening dusk.


I used a Canon 60Da camera with 15 mm fisheye lens to record a wide view of the sky. Cloud occasionally obscured the comet, before covering the whole sky.


I used a Sony A7s on a driven mount with 100 mm lens focused on the comet. Here the view is unusual in that the camera was in portrait mode but the video shows it in landscape, meaning that the clouds appear to fall downwards. This framing was to capture the tail most effectively. The image below the video is formed from a section of the latter. The light stripes on the left are clouds drifting overhead. Although the image is not a clean as I would like and processing has added some colouration to the corners, it does nonetheless show two tails each over 10° long!




Neil Short, 17 July 2020

Image taken near Mundon, Essex with a fine clear sky to the N-NW. The comet appears above the lights of Maldon. The bright star to the far right is Capella. Canon 100D, 5.3 s exposure, ISO 1600, 18 mm lens at f/4.5.



OASI Observing Trip To Sutton Heath, 17 July 2020. Report by Andy Gibbs.

On Friday 17 July, four members of OASI arranged to meet at Sutton Heath picnic site at 21:00 UT to observe and image Comet NEOWISE. The site was situated near a road but offered a good view to the northern horizon and was relatively free of light pollution. I was joined on site by OASI members Paul Whiting FRAS, Martin Cook and Joe Startin, and by two non-members who were also aiming to observe and image the comet. We could see Jupiter and Saturn to the south through the trees behind us. The sky was mostly clear, with the main bank of cloud moving away towards the east, leaving a small amount of high cloud.

We first spotted the comet in binoculars at around 21.30 UT and, shortly thereafter, it became obvious to the naked eye. It had dimmed slightly from when I had previously observed it on Sunday 12 July. We observed and imaged the comet until 23:00 UT, when we packed up and left. When I arrived back in Ipswich, it was mostly cloudy.

I captured the following image at 22:44 UT. Canon 1200D, 18-55 mm lens at 24 mm, f/5.6, ISO 1600.


Martin Cook captured the following image at 22:40 UT. Canon 1100D, 30 s exposure, ISO 1600, 150 mm lens at f/5.6.



Olaf Kirchner, 13 July 2020

Images of the comet taken from Genolier in Switzerland using a Canon 60D camera.





Mike Harlow, 13 July 2020

I used a 300 lines/mm transmission grating on the front of a 55 mm camera lens to capture a low resolution spectrum of the comet. Despite the yellow appearance of the comet in images, the characteristic Swan bands (typical of a comet) are present, with strong sodium emission too. Spectrum taken at 00:50 UT on 13 July 2020.


Other spectra are available! For example:


Nigel Evans, 12-13 July 2020

My Brinno TLC 200 Pro time lapse camera did a fine job of catching the comet from my home.


Meanwhile I ventured into the countryside to my "spot" north of Ipswich. When I arrived, at about midnight, there was somebody already parked there. I drove past and parked in the next passing place and started to unpack my equipment. As I was doing so, the parked car moved off and came towards me and the driver slowed and asked "are you after the comet?" We got talking, and it turned out that she lives nearby, is interested in astronomy (but is not a member of OASI) and had made the journey specifically to see the comet. She was thrilled as this was the first comet that she had seen with the naked eye. She left and I continued setting up.

I set up my Sony A7S with 35 mm lens to provide a wide-angle view of the passage of the comet across the northern horizon. The sequence went well but it shows that the observing site is not very dark. The horizon was clearly visible together with lights, likely of Diss, some 20 miles away. Also the air did not seem to be clear: when the last quarter Moon rose at about 23:45 UT, it appeared a rather dull orange-brown. The video also shows noctilucent clouds in the distance.


I recorded the video below with the Sony A7S camera with 100 mm lens, hoping to catch noctilucent clouds growing and enveloping the comet. Sadly, this did not happen.


The following is a stack of images taken with a Canon 60Da with 200 mm lens. In addition to the curved dust tail, it starts to bring out the ion tail - this is not seen in single exposures. The feature pointing downward from the head is a horizontal cloud.


The following is a stack of images taken with the same camera using a 100 mm lens. It shows a dust tail some 10° long, far in excess of the 2°-3° visible in binoculars. The amount of detail visible in the tails is interesting, so much so that a cropped and larger scale version of the same picture is shown below. Both tails exhibit striations (linear features): they are visible along the length of the ion tail and are apparent in the dust tail at the end distant from the coma. The images have been processed to track the comet (causing the stars to appear trailed) to help make the striations visible. Initially, I wondered if the striations were in fact an artefact of image processing, but when people like Michael Jaeger and Gerald Rhemann post pictures exhibiting similar features, I concluded that they are real.




Mike Whybray, 12 July 2020

I photographed the comet on 12 July at 22:37 UT from my back garden in Nacton. Canon EOS550D with zoom lens set to 55 mm f/5.6, ISO 1600, 8 s exposure. Unfortunately I forgot to turn on the automatic dark frame subtraction so there are a few hot pixels! The comet was very easy to see with the naked eye and looked very fine in binoculars.



Mike O'Mahony, 12 July 2020

The following image was taken from Priory Road, Felixstowe at 22:30 UT on 12 July. EOS 6Da camera on tracking mount, 130 mm lens, 11 s exposure, ISO 2000.



Paul Whiting, FRAS, 12 July 2020

I first attempted to observe the comet at 02:00 UT on 11 July. Unfortunately, the sky was far too bright to see the comet, but I did see some noctilucent clouds. I eventually caught the comet at 01:00 UT on 12 July, after a short drive to escape the light from Felixstowe Docks.

The following image was taken with a Nikon D3200 with 14 mm wide-angle lens, f/2.8, ISO 1600, 6 s exposure.



Andy Gibbs, 12 July 2020

I observed the comet 01:00-01:50 UT from an upstairs window of my house. It was easy to spot with the naked eye, even though my view towards the north is compromised by light pollution. It was a magnificent sight in 10x42 binoculars.

The image below was taken at 01:40 UT. Canon 1200D with 18-55 mm standard kit lens, 8 s exposure at ISO 1600.



Nigel Evans, 12 July 2020

The following image was taken with a 90 mm Megrez refractor with a focal length of about 450 mm. The comet is too big to fit the field-of-view. Also included are insets of the head, showing the brighter inner part of the comet.



James Appleton, 12 July 2020

My northern horizon is very restricted. However, on the morning of 12 July at 01:15 UT, I was able to see the comet with the naked eye through a gap between the houses across the road. The comet was unmistakable, the coma and nucleus appearing initially as a "fuzzy star". As I became increasingly dark adapted, I could discern the tail too.


Martin Cook, 11 July 2020

I first saw the comet through the bedroom window at midnight UT low down in the north. It was too low to photograph from the garden so I drove to just north of Ipswich to gain a better northern horizon. The comet was easily visible to the naked eye, even when driving.

The image below was taken at 01:02 UT, from just north of Ipswich. Canon 1100d, 5 s exposure, F5.6, ISO 1600, 160 mm FL.



Alan Smith, 11 July 2020

Alan's all-sky camera captured the comet above the northern horizon in several frames in the early hours of 11 July 2020. The following image, taken circa 00:41 UT, also shows a passage of the ISS (International Space Station through Cygnus.



Nigel Evans, 10-11 July 2020

The following image, captured with a driven Sony A7S camera and 100 mm f/4 lens, is a single frame, taken at 23:13 UT; note that is shows no trace of the comet's blue ion tail.


By way of contrast with the above, the following image, captured with the same equipment, is a stack of 31 frames taken 23:16-23:31 UT; it begins to show the ion trail.


The following video, again captured with the same equipment, taken from just before midnight UT on 10 July to just before 02:00 UT on 11 July, shows the comet rising above the northern horizon. The video stops at nautical twilight (the Sun 12° below the horizon) when the brightening sky made the tail inconspicuous. At the end of the video, noctilucent clouds were visible approaching the comet, but dawn arrived before I could capture an image of the comet through the clouds.


The following video was taken with a fixed Canon 60Da camera and 35 mm lens. I set up the camera in haste - hence the crooked horizon - hoping to capture the comet through noctilucent cloud. I failed in this, but did record the comet close to noctilucent cloud. The image immediately below the video is a single frame near the beginning of the sequence.



The video below is a time-lapse taken with a static Brinno TLC 200 Pro camera from my home (indoors). To my surprise, it records both the head and tail of the comet. Noctilucent clouds are visible at the end of the video. The initial segment of the video is marred by reflections from street lights (the problem stops at approximately 00:15 UT when the lights are switched off). Immediately below the video is a single frame from the sequence: the image of the comet is tiny, but then so is the camera!




Olaf Kirchner, 10 July 2020

Image of the comet taken from Genolier, Switzerland. The star above and to the left of the comet is ψ2 Aurigae. Taken at 02:26 UT. Canon 60D with 300 mm f/5.6 lens, 2 s exposure, ISO 1600.



Nigel Evans, 06 July 2020

Due to the weather, the first opportunity to attempt to observe the comet from Suffolk was the morning of 06 July, coinciding with a full moon in the south next to Jupiter and Saturn. The evening of 05 July was clear with a fine display of noctilucent clouds. It was forecast to be clear all night so, grabbing the opportunity, I set off from home just after 01:00 UT to search for the comet. I wondered what I was doing: not only was it very windy but the predicted clear skies were full of fast moving clouds! At my observing site just north of Ipswich, providing a clear northern horizon, I wondered whether to set up my kit - Polaris was visible only intermittently and the site was next to a tall old tree (I envisioned the headlines "High Winds In Ipswich: Falling Tree Kills..."). In the end, I set up two driven cameras, aligned approximately on the Pole Star. Approximate alignment would be adequate for the short exposures required by the immediate pre-dawn sky.

The comet was invisible to the naked eye, marginally visible in binoculars, and well-captured by my cameras. The video below was taken with a Sony A7S camera with 100 mm f/2 lens. The first section is the full frame view; the second is a 1620x1080 px cropped version. Initially, the comet is at an altitude of only 3° and the Sun at -12°. A still from the early part of the sequence shows the comet to have a tail of some 15 arcminutes or so in length.


After capturing the video, I attached the camera to my 90 mm f/5 Megrez. Again due to cloud, I was forced to accept approximate alignment on Polaris. The instrument was more susceptible to the wind than the combination of camera plus telephoto lens and, indeed, wind ruined several frames. The image below shows that a single exposure clearly captures the nucleus and tail. As dawn approached, the brightness of the background sky increased, causing the tail to disappear. Stacking frames from the video, captured earlier, while the sky was darker, shows more detail in the tail.