Orwell Astronomical Society (Ipswich)
Starlink Satellites, 04 January 2020 - 10 March 2022
Starlink is a collection of thousands of satellites being deployed by SpaceX into low Earth orbit to deliver broadband Internet services. A test launch on 22 February 2018 placed two satellites into orbit. The first full-scale launch, used to test aspects of the system, took place on 24 May 2019 and placed 60 satellites into orbit. Launches of operational satellites, in groups of up to 60 (a group is referred to as a constellation), began on 11 November 2019. Below, observations are grouped initially by launch number (e.g. L1, L2,...) and, from late 2021, by group number (e.g. Group 4-3, Group 4-4,...): this reflects the numbering of launches by Starlink.
Starlink Group 4-10 was launched from Cape Canaveral on 09 March 2022, on a southbound trajectory. The launch contained 48 satellites. Fourteen hours after launch, the satellites passed over the UK.
The following video shows a fisheye view of the pass, somewhat speeded up, as the satellites emerge from the Earth's shadow in Ursa Major. The brightness of the satellites when they emerged from shadow was similar to that of the stars in Ursa Major; however, by the time they had reached Cygnus, they had faded considerably. This is in marked contrast to the pass of Group 4-11 on 26 February (see below) when the satellites were brighter than the brightest stars.
The following video shows satellites passing through Ursa Major then Draco.
The following video of the pass was recorded with a less sensitive camera, a Canon 60Da and 200 mm lens. The effective aperture is 50 mm, so more light enters the sensor than with the A7S, offsetting the reduction in sensitivity. At the end of the video is a still from the sequence that just fits the entire train within the field-of view. I count 47 separate objects, but one is suspiciously fat, perhaps being two satellites orbiting in close proximity.
Starlink Group 4-11 was launched from Vandenberg Air Force Base on 25 February 2022. Twelve hours later, its 50 satellites appeared over the horizon seen from eastern England, emerging from the Earth's shadow in Ursa Major in reasonably dark, clear skies.
I took the following video with a Sony A7s camera and 100 mm lens. it comprises three short clips showing the train of satellites progressing though different areas of the sky in Ursa Minor then Cygnus.
I recorded the following video with an A7S camera and 200 mm lens, showing the satellites at a higher scale. It proved difficult to align the camera successfully, due to operating in the dark and the camera showing more than was visible by eye, within a 10° x6° field of view. I could count only 45 of the 50 satellites, along with a some tumbling objects both before and after the train.
The train was exceptionally bright. It passed close to Deneb, at magnitude 1.25, and was brighter than the star. It looked like a luminous stick some 6° long flying through the sky, becoming foreshortened towards the horizon.
The following image is a stack of 13 consecutive 60 s frames, spanning the period 05:10:24 - 05:23:56 UT. Camera details: ZWO ASI294 camera with 4.5 mm Sigma fisheye lens, f2.8, gain 250, colour, rotating shutter, 16 BPS 50/50 open/close. It shows the Starlink satellites above centre and a passage of the ISS, some 10 minutes later, below centre.
The following image is a stack of four consecutive 30 s frames, spanning the period 05:11:24 - 05:13:25 UT. Camera details: ZWO ASI 178MC with Fujinon 2.7 mm CF2.7HA-L1 fisheye lens, f1.8, gain 200, colour. It shows the Starlink satellites and an aircraft trail (middle to left of centre).
At 14:44 UT on 21 February 2022, the 100th launch of a Falcon rocket took place at Cape Canaveral. (The launch was the the 11th of the particular first stage.) The payload was 46 Starlink broadband satellites comprising Group 4-8.
Cloudy weather on the morning of 22 February prevented the satellites being seen from the UK, and the next opportunities to observe them were on the morning of 23 February. In fact, the satellites turned out to be very much brighter than the expected magnitude 4.4, and were responsible for reports of a "fireball" over London.
The following image is a stack of three consecutive 60 s frames, spanning the period 04:33:28 - 04:36:59 UT, from Alan all-sky camera at Grundisburgh. Camera details as above.
Alan took the following video of the event with a simple eyeball camera.
The following image is a stack of three consecutive 30 s frames, spanning the period 04:33:28 - 04:34:59 UT, from James Appleton's all-sky camera in east Ipswich. Camera details as above.
Nigel rose early on 23 February to observe the satellites on their second pass over the UK that morning. Venturing outside at 6.00am the sky was hazy and everything felt very damp. With the Sun being only 8° below the horizon, dawn was rapidly approaching and Arcturus was the only star visible, so it was uncertain whether the satellites would be visible.
The following video, taken with a Sony A7S camera and 50 mm lens, shows the entire group of 46 satellites passing through the stars of Boötes. There are 43 distinct bright dots, but a couple appear larger than the rest and likely represent multiple satellites.
The following video, taken with a Sony A7S camera and 100 mm lens, shows the group in more detail. The video is in three segments. The first is a long range view taken when the satellites were low in the west in Leo, invisible to the naked eye. The second shows the satellites passing overhead in Boötes, and shows the objects much more clearly, and the third was taken as they descended towards the eastern horizon. All 46 satellites are visible.
The videos show more than could be seen with the naked eye. The "string-of-pearls" effect was visible only when the satellites were overhead and, even then, was not prominent; this was because of the brightness of the sky.
Starlink constellation 4-7 was launched at 18:13 UT on 03 February 2022 and became visible from the UK early the following morning.
With a Starlink launch, normally the launch rocket, a Falcon 9, flies north-east up the eastern seaboard of the US and releases 60 satellites into orbit which then become visible over the UK some 20 minutes later. However, the current series of Group 4 launches is towards the southeast, necessitating a dog-leg path to avoid passing over land. This route has not been used since the 1960s, and provides better winter weather conditions for recovery ships to operate. However, the route impacts the load capacity, and launch 4-7 carried only 49 satellites.
In contrast to many previous launches, the satellites were not all of the same brightness: many were around magnitude 2, sometimes becoming brighter whereas, towards the back of the train, others were not visible. The satellites also spread out more quickly than previously, so I have speeded up the video by combining frames in groups of five. At least two satellites provided a specular reflection, presumably from solar panels: one is visible in the video below. I counted 52 objects in the video, of which at least four flash in a way characteristic of free-flying rods used to retain the satellites before release.
Postscript. What I did not realise at the time was that I had witnessed the aftermath of a massacre - the reason for the wide separation and uneven illumination of the satellites was that the bodies were dropping out of orbit! A geomagnetic storm hit the Earth's atmosphere shortly after launch, causing the upper atmosphere to heat and swell. As a result, the drag on the satellites increased, causing them to de-orbit. Three weeks after my observations, 38 of the 49 had been destroyed.
On 14 March 2021, launch L21 placed another 60 satellites into orbit. They were not initially visible from the UK. By 24 March they had come into view and I decided to try and record them. They were binocular objects (magnitude circa 5) and well spread out. I recorded them, but have not made a time-lapse video.
On 24 March 2021, launch L22 carried another 60 satellites into orbit. The following day they made an early morning pass but were at low altitude to the east and far away and I saw nothing. On 27 March, they made a pass at higher altitude, approximately 30° maximum. The 60 satellites were scheduled to pass within 70 seconds. Conditions were not ideal as the Moon, nearly full, was still above the horizon, causing brightening of the sky, and there were wispy clouds.
The following video, taken with a 35 mm lens, is a relatively wide-angle view towards Ophiuchus in the SW. The clouds in the video appear much more prominent than they were in reality! The satellites emerge from the Earth's shadow at the right: although more and more emerge from the Earth's shadow, it is not possible to see all 60 at once, as the first disappears from the frame before the last emerges. However, the still shows about 55 satellites.
The following live-speed video, taken with a 100 mm lens shows the satellite stream in greater detail. The view is of the Aquila-Ophiuchus border. It shows 60 satellites. Three of the bodies are tumbling: one about one third the way along, one trailing the offset satellite, and the third trailing after the last one of the main train.
The forecast was for clear skies in the early hours of 30 March, so I got up to see if, six days after launch, the satellites had become invisible. In the SW, the Moon, just past full, was making the sky bright. I was able to position my camera so as to obscure the Moon behind the washing line so that it did not appear in the fish-eye view!
The satellites, now orbiting at an altitude of approximately 300 km, were still visible, all with magnitudes comparable to those of the naked-eye stars of Ursa Major. The following videos, taken with a 15 mm fisheye lens and a 35 mm lens show the passage. It took nearly three minutes for 59 satellites to pass virtually overhead; the videos start shortly before the main train, and omit a solitary initial satellite that appeared approximately 80 seconds earlier (indeed the predictions for the satellites of L22 include only 59 members). The videos are running at 3x live rate.
Launch L20 was at 08:13 UT on 11 March 2021. The 60 satellites were ejected from the carrier one hour later. It was daylight and completely cloudy over the UK, so there was no immediate observing opportunity.
The following morning was forecast to provide an interesting viewing opportunity as, at around 05:30 UT, all the satellites of L20 would emerge from the Earth's shadow, strung out in a line. It would be twilight, but the satellites are bright and it might be possible to observe them. They would pass Arcturus, then appear overhead at about 70° altitude, then pass Vega. Circumstances would be similar to those for L17 one week earlier (report above).
Unfortunately the weather forecast for the event was not good, and it turned out to be accurate. I got up to observe the passage: although cloud coverage initially was not total, by the predicted time of the passage, it was. I saw no satellites. I could see some clear sky to the west, and observers there may have had better luck.
Initial predictions for 13 March were for reappearance of the satellites from the shadow of the Earth at 05:35 UT. Later predictions, on the evening of 12 March, indicated reappearances some 10 minutes earlier, with the satellites passing directly overhead. In the event, the sky was relatively clear but it was extremely windy. Unfortunately, I did not spot the satellites until they were nearly overhead, passing through an unremarkable area of the sky across the constellations Draco and Hercules. I captured 56 of the satellites on two Sony A7S cameras.
The following video was taken with a Sony A7S camera and 50 mm lens. The FoV is approximately 22x39°.
The following video was taken with a Sony A7S camera and 100 mm lens. The FoV is approximately 11x19°.
The videos above show the satellites against a generally uninteresting area of sky which makes it difficult to judge the image scale. On the morning of 14 March, there was an opportunity to capture the satellites passing through one of the most recognisable parts of the sky, the tail of Ursa Major. The results are below; both videos are presented at the original resolution (1080) but are speeded up x2 to reduce the file size. It was twilight, with the Sun only 8° below the horizon, and only the brightest stars are visible.
The following video, made with an A7S camera with 50 mm lens, shows the entire constellation of 60 satellites taking approximately 70 seconds to pass through the tail of Ursa Major.
The following video, made with an A7S camera with 15 mm fisheye lens, is intended to illustrate what it is like to look up into a clear sky to see all the satellites in the constellation at once. All 60 satellites are present in the video, although the resolution of the lens and video mean that close examination is necessary to see some of them.
The UK has not benefitted from early visibility of recent Starlink launches, and gloomy winter weather also restricted observing opportunities. By the time recent launches have come into view for the UK, the satellites have spread out and climbed in altitude so are harder to see.
However, the morning of 05 March provided a good opportunity to image the satellites from L17, launched at 08:24 UT on 04 March 2021, before they spread out.
A couple of really bright satellites appeared first. Looking toward the horizon where the rest would emerge from the Earth's shadow, I was amazed to see what looked like an approaching line of light: it was the remainder of the satellites, not resolved into individual bodies!
The video below shows the main group passing two distinctive stars, first Arcturus in the west then Vega in the east, both clips at live rate. The field of view is approximately 39°x22°.
A second camera recorded the passage at twice the scale. In the video below, well over 50 satellites can be counted. The second half of the video, with a brightening sky, is shot towards dawn, with the Sun only 9° below the horizon. The field of view is approximately 11°x20°.
The morning of 04 November brought the first frost of the winter. It also provided an opportunity to capture the satellites from L13 (launched on 18 October 2020). An 18 day old Moon in Taurus resulted in a bright sky bright.
The passage of the satellites was underwhelming. The leading satellites were binocular objects but, after a while, a few were visible to the naked eye at magnitude 2, rivalling the stars in Ursa Major.
The video below shows 58 satellites from L13, several from Space X constellations launched previously, and other satellites, not all of which could be identified. In the video, first there is a section showing the passage at x20, then a frenzied version at x100, then finally a clip in real time. The video shows more detail than was visible to the naked eye.
Launch L12 was on 06 October 2020. Unfortunately, dismal weather prevented imaging the satellites until the morning of 25 October. The date was almost the last opportunity to capture the objects making a morning passage, after which they became visible in the evening sky, with individual satellites spread out much further.
On the morning of 25 October, clouds had cleared but the sky was not transparent: it looked miserable and felt very damp. Fainter naked-eye objects such as Praesepe were not visible. Fifty-six of the 60 satellites emerged from the shadow of the Earth in Gemini and Taurus during a period of some 12 minutes. Most were bright, some rivalling Castor (magnitude 1.6) in brightness, and I could see perhaps six at any one time.
The first part of the video below shows all 56 satellites, speeded up by a factor of 20. It includes several other satellites, including other Starlink satellites from previous launches, but I was not able to identify all of them. Then there is a clip speeded up even faster: x100. Lastly is a short clip showing the motion of the satellites in real time. The overall view shows much more detail than could be seen with the naked eye.
In the early hours of 20 September 2020, I recorded the latest (as I write) set of Starlink satellites, L11, launched on 03 September. The constellation had spread out and, while there was some clumping, it was predicted to take 18 minutes for 58 out of the 60 satellites launched to pass overhead.
I expected to see faint dots visible only in binoculars with a handful that might be visible to the naked eye. I waited for the first one to emerge from the Earth's shadow and was pleasantly surprised that it was visible to the naked-eye. Then several more appeared, visible by eye. It started to look as if all the satellites would be bright, but a quick check in binoculars revealed in addition fainter satellites, invisible to the naked eye. The brighter satellites matched nearby Mirfak (magnitude 1.8) in brightness, possibly brightening as they moved towards sunrise.
A driven camera recorded many satellites but the field of view was too narrow to capture their lateral spread. A stationary camera with a wider field of view recorded all 58 satellites, 37 bright and 21 faint and, in addition, four satellites from previous launches, appearing coplanar with those of L11, various other Starlink satellites and other satellites and two meteors. The four satellites coplanar with L11 orbit at an operational height of 550 km, with an orbital period of 95.64 minutes, and move more slowly than the L11 bodies.
There are two sub-divisions of satellites within those of L11, those currently at a height of about 380 km with a period of 92.15 minutes, and a second, smaller group at an altitude of 360 km with a period of 91.80 minutes. The two groups have started to separate due to the differing orbital velocities and now follow two slightly different tracks. In the video below, the former group appears first, then members of the second group appear, at slightly higher altitude. The first part of the video is speeded up x20 relative to live. This is repeated in the second segment at x100. The final segment is at live rate (x1), true to what I observed, showing five bright and one faint satellite.
The morning of 06 September 2020 was the first opportunity to observe the satellites from L10 launched on 18 August. When I got up there was a long bank of cirrus cloud drifting by, well-illuminated by the 18-day old Moon. The satellites had started to spread out but the main group of some 35 was predicted to pass by in less than eight minutes. The bank of cloud moved away, only to be replaced by another one just at the critical time - how frustrating!
In the short clip below shown at x1 speed, I show only three satellites from the earlier part of the pass, one at approximately magnitude 4 and a pair at approximately magnitude 6. The stars at the top are the Hyades, including Aldebaran. Overall the spectacle was unimpressive, made worse by the back-lit clouds obscuring the sky.
It will be another week before satellites from the latest launch (L11, launched 03 September 2020) become visible in the morning.
On 09 September, I finally managed to record the satellites of L10 without clouds, passing virtually overhead by the Perseus Double Cluster. The spectacle was singularly unimpressive: of the 32 satellites that passed in some seven minutes, only three were visible to the naked eye, the remaining 29 being binocular objects, perhaps magnitude 5.
An incidental highlight was the capture in the video of a small meteor - it flashes by about eight seconds into the clip. I replay that section at the end of the clip at much slower speed.
The morning of 12 August provided the first chance of imaging the Starlink satellites from launch L9 on 07 August. Previous nights during the heatwave of early August all suffered from high level, obscuring cloud.
L9 contained 57 Starlink satellites and a pair of Earth observation satellites from BlackSky. All Starlink satellites launched now are fitted with sun visors to reduce their visibility to astronomers.
By the morning of 12 August, many of the satellites had separated from the main train, but 39 were scheduled to pass through Cassiopeia within 40 seconds. Unfortunately, I set too long an exposure time, ¼ s instead of 1/30 s and, with the satellites appearing so close together, in some cases, streaks caused by different satellites overlapped. In the below video I counted 36 satellites, including the straggler at the end. Some of the longer streaks are obviously caused by a pair of satellites, so I counted them as such. The remainder of the group are some 8 minutes behind and spread out.
The typical summer haze meant that the satellites were not visible to the naked eye. The first I saw of them was on the back of the camera viewfinder, then in binoculars.
On the morning of 13 August, there were two more opportunities to see satellites from L9: the first at 02:36 UT had better weather prospects than the second at 04:13 UT. I awoke at 02:15 UT and a quick check out of the window revealed stars. I went outside to find that much of the sky was covered in cloud - lots of little high, dark, almost stationary clouds. Even the Moon was obscured, but some bright stars were visible. I could discern Cassiopeia and, knowing that my cameras can record more than I can see, I decided to proceed.
The clouds were shifting and I was rather surprised to see a moving object in the electronic viewfinder; I looked up and could see that it was a satellite and that there were several more moving in the same direction. They were Starlink satellites! I was surprised to be able to follow a handful of them in the direction of the Moon.
The following video, taken using a Sony A7S with 50 mm lens, shows the unmistakable pattern of Cassiopeia and indicates how cloudy it was. Eleven Starlink satellites are easily visible, most continuing to be visible through advancing clouds. They were of comparable brightness to the stars in Cassiopeia, magnitude 2. The remaining satellites of Constellation 9 don't really show in the video.
I used a second A7s with a longer, 100 mm, lens to produce the video below. It shows the bright satellites and the advancing cloud-front. After the last bright satellite passes, faint satellites are visible in the gap above the top of the advancing cloud bank, until the gap closes.
The forecast for the earlier observation had been fair, but it turned out cloudy. The forecast for the later observation was grim. But I decided to stay up and have another go. I went outside periodically to check the weather, to find at times that the only things visible were the Moon, Mars, Venus and Capella. As it approached 04:00 UT, Cygnus was quite clear, but it was hard to discern other constellations, as the limiting magnitude seemed to be about 2.
When photographing Starlink satellites (other than with a fisheye lens) it is necessary to aim the camera in advance at where the satellites will appear. I chose an area in Andromeda, approximately due south. Just before the arrival of the satellites, I started scanning Cygnus, in binoculars, for moving objects. Sure enough, the satellites appeared and were in fact visible to the naked eye. I watched as they came into the field-of-view of the first camera, but not the second: it was not aimed correctly. A quick adjustment rectified the situation, but the second camera missed the first part of the passage. My mistaken aiming came about as follows. With the camera set to high sensitivity (ISO) and with a narrow field of view, I had found a set of stars that looked similar in the viewfinder to what I could see with the naked eye. In fact, the camera was pointing several degrees too low. In future I may use a green laser pointer to highlight the desired area of the sky.
The following video, taken with the camera with 50 mm lens, shows 14 bright satellites and a few fainter ones. The 14 bright satellites look comparable in brightness, if not brighter, than the labelled stars, which are all around magnitude 2.0-2.1. The limiting magnitude was around 5.
The initial six bright satellites are missing from the following video because of the pointing error. The clip starts with a faint satellite in the extreme bottom left (before the bright pair); thereafter I counted a total 23 faint satellites, making 37 in all. This includes 2 pairs that are very close together, one at 10 seconds, the other at 17 seconds. Stars are recorded to magnitude 7. www.heavens-above.com predicted a passage of 39 satellites.
On 05 July, I finally recorded the L8 satellite train, launched in daylight on 13 June 2020. However, with all the interest in comet C/2020F3 (NEOWISE), my report on the observation had to wait!
L8 launched 58 Starlink satellites and three Skysats. I recorded 46 satellites from the launch, together with several from the L3 launch. The majority were in one long group, with, in most cases, a satellite being about 20 s from its neighbour. Those not at 20 s intervals were in slightly lower, faster orbits. In the video is a short clip at the live rate, but the major part is speeded up and processed to make the satellites more visible. I did not edit the aircraft out of the video - they are easy to identify as there are few of them about!
I did not see the majority of the L8 satellites with the naked eye from my suburban location, as they must be magnitude 4 or 5, but binoculars easily showed them. So it seems that the "string of pearls" effect seen previously is likely to be a thing of the past, as Starlink is taking steps to reduce the impact of the satellites on astronomy.
Launch L7 was on 04 June and there were four passages of the satellites over the UK during the hours of darkness on the night of 05-06 June. Unfortunately, conditions were not ideal, with a full Moon, at low altitude in Scorpius, causing considerable glare in the south.
The first passage was in the early evening with the Sun only 8° below the horizon. I could see no satellites, either by naked-eye or in binoculars. I captured with a video camera a series of moving faint dots, as well as a couple of satellites that brightened to magnitude 3 or so. The spectacle was unimpressive.
The second passage was at much higher altitude, up to 80°, in a dark sky. There was not a lot to see, until one satellite appeared at magnitude approximately 0.5. Binoculars then revealed a very impressive train of faint moving dots; however, they were not visible to the naked eye. Light pollution from Ipswich and sky conditions combined to produce a limiting magnitude of approximately four. The resulting video is below: it shows 54 distinct bodies, as a well as a couple that look like unresolved multiples. By way of comparison, Alcor is magnitude 3.96.
The third passage was early in the morning of 06 June, again at high altitude, up to 75°. The sky did not look as clear as before. Again there was a prominent bright satellite, but the rest were binocular objects.
The fourth and final passage was in the morning twilight, with the added complication that the view was towards the full Moon. Several satellites were visible to the naked eye at magnitude one or thereabouts, but most could be seen only with binoculars.
In response to concerns from the astronomical community, SpaceX has introduced a policy of orienting the satellites en route to their operational orbits so as to minimise their impact on the night sky. See https://www.spacex.com/updates/starlink-update-04-28-2020/.
By 15 June, the satellites had spread out and appeared low down in the south-west after sunset. They were invisible to the naked eye, and could be seen with binoculars. I recorded 52 in less than 10 minutes, sometimes two or three appearing in the field of view at a time. Later that evening, there was was a passage of satellites from L6 - details above.
I generally use orbital elements, loaded into a planetarium program, to identify individual satellites. However as the satellites are climbing to working altitude, the elements rapidly become out of date. I found that two sets of data gave a different order to the satellites. Indeed, if the predictions show satellites to be, say, only one second apart, confidence is low that the order is correct. So in labelling the satellites in the videos I follow Eric Morecambe's stance on his interpretation of Grieg's piano concerto for André Previn "These are all the right satellites - but not necessarily in the right order!" (Morecambe and Wise Christmas Show, 1971).
On 05 June, starting at approximately 22:45 UT, I captured the second passage of satellites from L7. I used a 135 mm telephoto lens at f4 on a Canon 550D in video mode under clear skies. I recorded the video as 1920x1080 px then rotated and cropped it to 1080x720 px. heavens-above.com predicted that all satellites would appear in the range of magnitudes 1.8-2.2. However, in practice they appeared fainter than this so I increased the brightness and contrast of the video to make them more apparent; in consequence, it appears rather grainy.
The video is below. The two stars on the left are Mizar and Alcor in Ursa Major (magnitudes 2.23 and 3.99 respectively) and the video gives a good impression of the naked eye brightnesses that I observed - all but one satellite were rather dimmer than Alcor and the bright one was considerably brighter than Mizar. I could barely see the satellites by naked eye but they looked very impressive (a space armada!) in binoculars. I tried matching the timings on heavens-above.com with my video but couldn't obtain a good correspondence, so can only identify the bright satellite as around number 40 in the passage. (Satellite 20 in the sequence is tagged on heavens-above as a Visorsat model, i.e. it has a special sun-shield to help avoid reflections from the antenna.)
I expect that the majority of satellites were dimmer than predicted due to efforts by SpaceX to reduce visibility of the craft by angling them to reduce reflection of sunlight during the ascent phase. Perhaps something went wrong with the bright one?
The launch of L6 was unexpectedly bropught forward to 20:30:30 BST on 22 April 2020. This provided an excellent opportunity to witness the first pass of the carrier rocket in the evening twilight, some 20 minutes after lift-off. As the satellites are released some 15 minutes after launch, they were expected not to have separated sufficiently from the rocket to be individually visible.
I imaged the passage with a 600 mm telephoto lens on a tripod with a video head. Predictions for Ipswich showed that the rocket would pass close to Venus, providing a bright marker in the evening sky. Having found the rocket next to Venus, it came closer and rose to higher altitude making it harder to keep in the field-of-view. As it passed nearly overhead at an altitude of 74°, I could no longer follow it.
It's difficult to obtain good results tracking a moving object with a long telephoto lens and, indeed, the rocket appears to dance all over the frame. So I have picked through the video, keeping all the frames where the image is reasonably still, then centred them manually, and turned them into a video. Unfortunately, the time difference between frames is not fixed!
The video shows initially two Starlink objects, a long one and a point below and to the right and, much further to the right, Venus. The point is the carrier rocket. The long streak is a stack of 60 satellites, not individually resolved, after being released by the launch rocket. As they come closer the odd stars fly by from the top of the frame. Near the satellites some stray objects start to flash into view - they are retention rods that held the satellites in place on the carrier. The stack of satellites appears to rotate, but this is an effect of perspective as they pass overhead. Then I lose them before finding them again. By now the stack of satellites and the carrier are back-lit and have become one object again due to foreshortening, but four retention rods are clearly seen as separate items.
Below the video is a composite of selected frames, showing the evolution of the Starlink train as it passed overhead.
Opportunities were initially limited to see satellites from L6 once they were placed into orbit. However, an opportunity arose in the evening twilight of 24 April. Visually, I could not see anything, but a video showed a train of satellites low down in the south-west. The video below is a 7 s clip of the original recording, cropped 50% both horizontally and vertically. The lower pane is a contrast-stretched version of the original (cropped): the satellites are still hard to see. The upper pane is a sequence of differences between individual frames and a running median of nine frames.
I then applied further processing to individual frames of the video, all 1500 of them, to produce the still images below the video. The upper still is a sum of individual frames, showing a trail effect, with the satellites following one another through the sky. The lower still is a stack of 25 frames (one second's worth) aligned on the satellites. (The fact that they are moving at slightly different rates makes it not possible to achieve good results stacking a larger number of frames.) It shows 36 distinct satellites, with one or two looking like unresolved multiples. This aligns with the fact that the 60 satellites of the constellation have separated into a group of approximately 40 followed about a minute later by another of approximately 20.
There was another opportunity to observe satellites from L6 on 15 June. Some 40 satellites appeared in a regular procession with an interval of almost exactly 20 seconds. They were visible to the naked eye; this contrasted with satellites from L7 which were visible earlier in the evening, but required use of binoculars (see below). In part, this was because the satellites of L6 were at an orbital altitude of ~500 km compared to ~700 km for L7. While most of the satellites become visible within the frame, there are a few times (26, 28 and 30 seconds into the video) where the satellites flare at the right-hand edge of the frame. (Unfortunately, the right-hand edge is marred by an ugly green colouration, an artefact of compressing the video from 1080 to 720.)
My video of the passage of satellites from L5 on 21 April is below. The two brightest stars in the lower left are Castor and Pollux. The video starts at 20:00 UT. It is cropped and resampled from a sequence of full frame images taken with a Canon 550D and Samyang 14 mm lens at f/4, 2 s exposures.
The following time-lapse sequence shows the passage of satellites from L5 above the stars of Leo on 21 April. It spans the period 19:58-20:14 UT. It was recorded at 6240x4160 pixels then cropped to 1280x720 pixels. Taken with a Canon 6D camera and 24-105 mm zoom lens at 24 mm, f/5.6. ISO 4000.
On 07 April, I finally saw the Starlink satellites from launch L5 (18 March 2020). Conditions were mixed: the atmosphere was cool, calm, silent and still, but the sky was hazy and moonlit with cirrus clouds. I set a camera running, taking images to make a time-lapse movie. I had initially intended to set up a second camera in video mode, but concluded that conditions did not warrant it.
Usually, with the camera running, I watch the satellites pass overhead, but this time I could not see them. Nevertheless, the camera recorded them together with some additional "features" including a large brightness gradient across the field of view and moving cirrus clouds. (I have removed the gradient in the second part of the video, to give a much more pleasing appearance.)
I don't know why the satellites were so faint. Towards the end of the video, Starlink 80 (from L1) can be seen passing above the path of the satellites from L5, and appearing much brighter. Curiously, heavens-above.com does not include magnitude estimates for constellation 5, whereas it does for all the others.
By 19 April, heavens-above.com was providing magnitude estimates for L5, indicating that the satellites would be exceptionally bright. I recorded the passage that night, half expecting another disappointment. Unfortunately, I was late in starting, so missed the first few satellites. I was stunned by how bright the satellites appeared, some appearing roughly as bright as Regulus.
The video below has not been polished - I have not removed the aircraft, nor labelled the satellites.
The passage of satellites from L5 on 20 April was much different; in fact it was a disappointment! I recorded the passage, using exposures of two seconds, rather than four seconds used on 19 April, other details being the same. In the 20 minute interval from 22:00 - 22:20 BST, some 42 satellites passed through Ursa Major but a video shows only seven and a multiple exposure only 10.
The passage on 21 April occurred during evening twilight. This made it tricky to record because of the variation in background light level as night fell, necessitating more sophisticated processing of the images than had previously proved necessary! In the video below, the left hand pane is a view of the sky as night falls: it is difficult to see the satellites as the Sun is only 9° below the horizon. (However, dust on the sensor is very clear!) The image was captured using a fish-eye lens with a very wide field of view, showing a wide variation in brightness across the sky. The right hand pane shows the sequence of differences between each frame and a running nine-frame median, highlighting moving objects against a much flatter background.
By mid-February 2020, satellites from launch L3 (29 January 2020) had come to visibility in the mornings. The morning of 12 February, although very cold, presented an opportunity to image the objects. The satellites came out of the Earth's shadow at an altitude of about 20°, close to the Moon. The main group consisted of 31 satellites, all in a line with a typical spacing of about 12 seconds. It was possible to see at least 10 satellites at the same time - the sight of them moving as one relative to the stellar background was quite surreal! Towards the end of the pass, one of the satellites was moving visibly faster than the others and overtook another. Currently, most of the satellites are in a circular orbit at an altitude of about 340 km, orbiting the Earth 15.75 times a day, climbing towards an operational altitude of 500-550 km. Starlink 1179 is in a lower orbit of 279x291 km, circling the Earth 15.95 times a day, so appearing to travel 1.3% faster.
I videoed the passage of the satellites through the border of Corona Borealis - Serpens. Equipment used: Sony A7S camera, driven, 100 mm telephoto lens at f/2, ISO 16,000. Some acceleration of the event was necessary to reduce the size of the video file. The satellites are nominally in the same orbit, but from the rotating Earth they appear to sweep through a band of the sky. The impact of the satellites on astronomy, flashing through the fields-of-view of telescopes around the word, remains to be seen.
On the morning of 19 February it was again clear and I took the opportunity to record the passage virtually overhead of the constellation. I used a fish-eye lens. Although the satellites are launched in groups of 60 into a low earth orbit, they start to spread out as they propel themselves into their working orbits at an altitude of 550 km. On 19 February, the main group contained 28 satellites that passed in about 8 minutes. The movie below captures most of the satellites from approximately 05:40:30 to 05:49:50 UT. The still frame, taken at 05:47:11 UT shows 14 satellites. Equipment used: Canon 60Da camera, 8 mm fish-eye lens f/4, ISO 3200, 2 s exposures.
On 16 March, there was an opportunity to catch a train of satellites from L3 passing directly overhead. Forty of the 60 satellites passed over in a group, one every 25-27 seconds or so, with eight visible at any one time. At this time the objects were mainly in an intermediate circular orbit at an altitude of 380 km.
The video below was taken using a driven mount. The evening sky was not particularly clear, with cirrus cloud present. Again I used a fish-eye lens, which meant that aircraft were a major problem, and removing them from the video was tedious!
The morning of 12 March was not very clear, the Moon was up and it was very, very windy, but it was the first opportunity to observe satellites from launch L4 (17 February). The main pack (about 44 satellites out of 60) passed by in 18 minutes. They were mostly 25-27 seconds apart, not as close as some earlier launch groups have been, but it was still possible to see six or more at once. All bar one could be identified using predictions from heavens-above.com: the exceptional one moved like all the others but there was no associated prediction. All the satellites passed close to the star Pherkad (γ Ursae Minoris, magnitude 3.05) which most of them matched in brightness.
I normally use a driven mount when recording Starlink satellites, but I forgot to switch it on initially! As a result, the stacked composite near the beginning of the video shows star trails.
Satellites from launch L1 (11 November 2019) were well-placed for observation in early January 2020. The night of 04 January was clear with a first quarter Moon, but not particularly transparent. Most satellites from the launch passed virtually overhead. I was able to record 41 of them, including three slightly out-of-plane with the main group, along with several other satellites that passed through the field-of-view (and two aircraft).
In the animation below, the Starlink satellites pass from 2 o'clock to 8 o'clock. Most were invisible to the naked eye in the moonlit sky, but two were very very prominent, with brightness similar to the stars in Cassiopeia.