Comet c2023 A3 Tsuchinshan-ATLAS viewing with frustrating UK cloud

Last week we had the incredible Aurora display with vibrant colours pulsating across the evening sky. This week’s viewing could include a more subtle cosmic visitor, Comet C/2023 A3 (Tsuchinshan–ATLAS). After months of speculation about how this comet would look, it has emerged as a bright comet in the western evening sky.  The tail is illuminated by sunlight but we need partial darkness to view it. Monday evening might be the best chance for some parts of the UK. If you are heading out, 19:30 until 20:15BST have been good times so far . 

 
Oct 8th @MissionSoho (The Solar & Heliospheric Observatory, is a project between ESA and NASA to study the Sun from its deep core to the outer corona and the solar wind) witnessed two Coronal Mass Ejections. The big white streak on the right (above) is Comet A3 entering the scene. An entertaining photobomb in the view of the sun from space. The CMEs lead to the stunning Aurora show of the 10th October.

“Comets are large objects made of dust and ice that orbit the Sun. Best known for their long, streaming tails, these ancient objects are leftovers from the formation of the solar system 4.6 billion years ago.” NASA

There are various factors to balance for a good view, the first being a clear low view of the western sky. Binoculars will help although it should be possible to see it with the naked eye. You will need to search the western sky just after sunset and not have any trees, buildings or hills in the way.  The comet has been rather low down but will be slightly higher each evening, so away from the afterglow and moving into darker skies. However, each evening it is further away and so more faint. Its closest approach to the Earth was at the weekend but Oct 14th and 15th would still present good opportunities, even until the 20th.

Thanks to Southern Storm (Dorset) from the Netweather community forum

Of course, the Great British weather will have to play ball, more on that later. As it is ‘close’ to the Sun in the sky, ‘forward scattering’ may make the comet seem brighter as the comet’s dust particles redirect sunlight towards your eyeliner.

"I headed out on Monday evening but didn't manage to see the comet as I think I was too early. There is a balance to be struck, that it is dark enough to see the comet but not too late that it has set, disappeared below the horizon. Also, I wasn't sure how low down it would appear and if a smear of cloud was masking the comet or not. If I went again, I'd be in place by 7:30pm." Jo

Comet over SE England on Monday 14th evening (Sprites in Netweather forum)

Seeing this comet is special because it is a long-period comet. Though the comet is very old, it was only discovered in 2023, when it approached the inner solar system for the first time in documented human history.  Comet C/2023 A3 (Tsuchinshan-ATLAS) was discovered separately in 2023 at the Tsuchinshan Observatory in China and a telescope in South Africa which is part of the  Asteroid Terrestrial-impact Last Alert System, (or ATLAS). 

NASA “The comet hails from the Oort Cloud, which scientists think is a giant spherical shell surrounding our solar system. It is like a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger."

If you are heading out, you should be in place about an hour after sunset. The Netweather Radar shows where the cloud is, seen above from mid afternoon Monday 14th.

Maybe scope out a good clear line of sight before you need to be set up. Wrap up warm for Monday night, less so in the mild air of midweek. Try to get some shelter if it is blustery so that your camera doesn’t wobble about. Take a tripod, or at least have a hard surface (like a car bonnet) to lean on). 

Stellarium app, looking west

Don’t be tempted to take camera photos or look at the sun before it has set. You need to know where is west, if you are looking at a compass get out of your car first. There is a bright star Arcturus in a Y-shape constellation, and left right near the horizon will soon be Venus. The Comet is between the two, if you drew a line, it would be halfway. If you can spot the PLough, that would be to the right (nearer the North Star) and higher, so follow the ‘handle’ left and down to the horizon, looking for bright Arcturus on the way. Focus centre on Arcturcus and either let your iPhone auto-choose Nightvision or on a Samsung try Pro settings in Camera. If you can adjust the ISO settings to 800, and seconds to 2 initially.

Sunset up and down the country runs from 17:57 to 18:09 depending on your location. The weather is not ideal. Monday evening looks most hopeful but only for some parts of the UK. A small low pressure is running across the south coast of England with plenty of cloud. There is an occluded front in the far NW of Scotland but in between there have been glorious blue skies and sunshine today and the best chance of clear skies for this evening (and for the next few days). It will be cold in the north but with light winds across the UK. 

By Tuesday there will be mild, more moist air from the south with a bit more of a southerly breeze and certainly more cloud. To the lee of high ground, there is a chance of breaks appearing and certainly for northern Scotland. By early evening there could be outbreaks of rain for Northern Ireland and the West Country. 

For Wednesday, there will still be a good deal of cloud in the mild, southerly flow., The blustery winds will ease by the evening and there will be some breaks, perhaps either side of the main thrust of rain and associated cloud. Elsewhere, it will be hit and miss for heavy, even thundery downpours or brighter breaks. 

More discussion and chat about the Comet 

Top image NASA/Matthew Dominick "Comet C/2023 A3 (Tsuchinshan-ATLAS) was about 44 million miles away from Earth in this photograph from the International Space Station as it orbited 272 miles above the South Pacific Ocean southeast of New Zealand just before sunrise on Sept. 28, 2024."