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Geminids Meteor Shower 2015

December 11, 2015 1 comment

One of the most active and reliable meteor showers, the Geminids, happens every year in mid-December. This year’s display promises to be a good one for those meteorwatchers with clear skies.

The maximum rate of Geminids is predicted to occur around 1800 on 14 Dec 2015, but peak rates normally persist for around a day, so the nights of 13 and 14 Dec are both good for meteorwatching. In addition. you’ll see plenty of Geminids from now until a few days after the peak.

When Gemini Sends Stars to Paranal  Image Credit & Copyright: Stéphane Guisard (Los Cielos de America), TWAN

When Gemini Sends Stars to Paranal
Image Credit & Copyright: Stéphane Guisard (Los Cielos de America), TWAN

There are a few ways you can maximise your chances of seeing some Geminids (see The What, How, Where, When and Why) but the best way is to get somewhere dark, like one of the UK’s International Dark Sky Places. I’ll be heading down to Galloway Forest in SW Scotland.

The Geminids’ radiant (the point in the sky where all the meteors appear to emerge from) rises at sunset, so you can begin your meteorwatch as soon as it gets dark enough. The Moon is only 3 days old at maximum so you’ll have no interference to your dark skies.

The number of meteors that you will observe every hour depends on a number of factors:

  • the density of the cloud of dust that the Earth is moving through, that is causing the shower in the first place;
  • the height above the horizon of the radiant of the shower, the point from which the meteors appear to radiate;
  • the fraction of your sky that is obscured by cloud;
  • the naked-eye limiting magnitude of the sky, that is a measure of the faintest object you can see.

The Geminids meteor shower has a maximum zenith hourly rate (ZHR) of  around 120 (the highest of any meteor shower). This is the number of meteors that you can expect to see if the radiant is directly overhead (the point in the sky called the zenith), and you are observing under a cloudless sky with no trace of light pollution.

However conditions are rarely perfect. In the UK, for example, the radiant of the shower will not be at the zenith; it will be around 10° above the horizon at 1800h, 25° above the horizon at 2000h, 40° at 2200h, 60° at 0000h, and at its highest of 70° at 0200h.

Assuming a clear night, the other factor is the limiting magnitude of the sky, a measure of the faintest object you can see. Man-made light pollution will be an issue for most people. From suburbia the limiting magnitude of the sky is ~4.5 (around 500 stars visible), so you will only be able to see meteors that are at least this bright; the fainter ones wouldn’t be visible through the orange glow. In a big city centre your limiting magnitude might be ~3 (only around 50 stars visible); in a very dark site like Galloway Forest Dark Sky Park the limiting magnitude is ~6.5 (many thousands of stars visible), limited only by the sensitivity of your eye. So in most cases it’s best to try and get somewhere nice and dark, away from man-made light pollution.

The calculation that you need to make in order to determine your actual hourly rate is:

Actual Hourly Rate = (ZHR x sin(h))/((1/(1-k)) x 2^(6.5-m)) where

h = the height of the radiant above the horizon

k = fraction of the sky covered in cloud

m = limiting magnitude

Let’s plug the numbers in for the Geminids 2015.

ZHR = 120 (maximum)

h = 10° at 1800, 25° at 2000, 40° at 2200, 60° at 0000, 70° at 0200h

k = 0 (let’s hope!)

m = 6.5 (if you get somewhere really dark!)

So your actual hourly rate under clear dark skies is

(120 x sin(10))/((1/(1-0) x 2^(6.5-6.5) = 21 meteors per hour at 1800
(120 x sin(25))/((1/(1-0) x 2^(6.5-6.5) = 50 meteors per hour at 2000
(120 x sin(40))/((1/(1-0) x 2^(6.5-6.5) = 77 meteors per hour at 2200
(120 x sin(60))/((1/(1-0) x 2^(6.5-6.5) = 104 meteors per hour at 0000
(120 x sin(70))/((1/(1-0) x 2^(6.5-6.5) = 112 meteors per hour at 0000

If you’re observing in suburbia you need to divide these numbers by around 4, and in bright cities by 10! Nonetheless, even in a city if you’re out at midnight during peak activity you’ll see around 10 meteors per hour.

Remember though that these numbers are assuming perfectly clear skies under perfectly dark conditions, and are assuming a peak rate of 120 at each of these times. It probably won’t be quite this good, but the bottom line is: there’s never a better night to see meteors!

Solar Eclipse 20 March 2015

January 15, 2015 Leave a comment

UPDATE: Teachers! Educators! Don’t miss out on the learning opportunity of a lifetime! This partial eclipse will be the best seen in Scotland and much of the UK since 1999, and the best until 2090. And you don’t need eclipse glasses to experience it. 

Indeed, looking at the Sun is a very minor part of the experience. The most incredible thing to happen on Friday morning will be the darkening of the day, as the Sun gets covered by the Moon and much of its light gets blocked out. This will create a dusk-like atmosphere; birds will start singing, insects will come out, flowers – if you can find any – may close up! This is such an unusual and rare event that I really hope every school pupil in the country will get the opportunity to experience it. The best time for this is straight after register (0900) until around 0945.

If you have eclipse glasses you could let some of the pupils use those but I understand that you probably don’t have many pairs and fear the younger children might not use them correctly. Don’t use them then! Just get outside, tell the kids not to look at the Sun, and explore the wonderful daytime darkness. I really hope you can turn this into the learning opportunity of a lifetime.

On the morning of Friday 20 March 2015 there will be a total eclipse of the Sun. Between 0830 and 1042 the Moon will pass across the face of the Sun, blocking out part of its light. The maximum extend of the eclipse will happen at 0934 for a few minutes.

A Total Eclipse of the Sun, visible from the Faroe Islands on 20 March 2015

A Total Eclipse of the Sun, visible from the Faroe Islands on 20 March 2015

Unfortunately the “path of totality”, i.e. those parts of the world that will see a total eclipse, is in the far north Atlantic and Arctic oceans. Residents of the Faroe Islands get a ring-side seat at the total eclipse.

Path of Totality, Friday 20 March 2015

Path of Totality, Friday 20 March 2015

That said, it will still be a dramatic event in the UK, south of the path of totality, as we will see a partial solar eclipse where the Moon blocks some but not all of the Sun’s light.

A partial eclipse from Anamosa, Iowa. Credit: Steve Wendl - See more at: http://astrobob.areavoices.com/page/112/#sthash.ElDDdLAg.dpuf

A partial eclipse from Anamosa, Iowa. Credit: Steve Wendl – See more at: http://astrobob.areavoices.com/page/112/#sthash.ElDDdLAg.dpuf

The further north you are in the country the more of the Sun will be obscured, but wherever you are in the UK it’ll look quite dramatic. Here’s a handy table showing what % of the Sun’s disk will be obscured by the Moon from where you are.

Town/City % Eclipse on 20 March 2015
Lerwick, Shetland 96.8%
Kirkwall, Orkney 96.6%
Inverness 95.6%
Aberdeen 93.9%
Glasgow 93.7%
Edinburgh 93.1%
Belfast 93.0%
Newcastle 90.7%
Liverpool 89.4%
Manchester 89.1%
Birmingham 87.3%
Cardiff 86.7%
London 84.4%

Compare this with the August 1999 eclipse, where totality passed across the SW of England. During that eclipse the further south you were in the UK the better. Indeed the SW of England and the Channel Islands saw a total eclipse.  I was in Glasgow and saw an 82% eclipse. For me, this eclipse will be even better. In fact for anyone north of Liverpool, the 2015 eclipse is better than that in 1999!

Town/City % Eclipse on 11 August 1999
Lerwick, Shetland 67.9%
Kirkwall, Orkney 68.7%
Inverness 76.8%
Aberdeen 77.6%
Glasgow 82.2%
Edinburgh 81.8%
Belfast 86.8%
Newcastle 84.8%
Liverpool 90.5%
Manchester 90.1%
Birmingham 93.5%
Cardiff 97.2%
London 96.6%

Wherever you are in the UK though it’s worth watching, but BE CAREFUL. Never look at the Sun directly, even when it’s eclipsed. Here are some safety guidelines for viewing eclipses.

Stargazing Hotel Breaks And Cruises 2015

December 20, 2014 3 comments

In 2015 I’m delighted to be hosting a range of stargazing events, from stargazing weekend breaks under some of the UK’s darkest skies, to a cruise to one of the most remote islands in the world, steeped in astronomy history.

Steve Owens’ contribution was perfect. We liked how he joined in with the guests at meals etc and held the group together. He has a gift of being able to convey his knowledge in terms easy to understand.His lecture with slides was really informative and interesting as was the enthusiasm he put into answering our every question or listening to our accounts of minor brushes with stars!!

Here’s a list of the hotels I run stargazing breaks at:

Glenapp Castle, Ballantrae, Scotland (Galloway Forest Dark Sky Park)
Kirroughtree House Hotel, Newton Stewart, Scotland (Galloway Forest Dark Sky Park)
Selkirk Arms Hotel, Kirkcudbright, Scotland (Galloway Forest Dark Sky Park)
Yarn Market Hotel, Dunster, Exmoor (Exmoor Dark Sky Reserve)

And here’s the cruise I’m hosting:

Stargazing and astronomy cruise, 4-22 May 2015, Cape Town to St Helena. On this stargazing tour you will have the opportunity to stargaze from a truly unique place – St Helena. The island is steeped in astronomical history, and you’ll visit the sites of Halley’s observatory (he of comet fame), as well as those of the other astronomers who have visited St Helena over the centuries. Its location near the equator means that virtually every constellation in the sky is visible at one time or another from St Helena, and visitors from the UK will be amazed to see a whole new collection of stars in the southern hemisphere that simply aren’t visible from Europe: the famous Southern Cross, the Magellanic Clouds, and the galactic centre of the Milky Way.

Here’s a list of the weekends I’m running throughout the year. Click the links for the hotels above to find out more or to book!

Stargazing weekend break, 20-22 February 2015, at the Yarn Market Hotel, Dunster, in Exmoor International Dark Sky Reserve

Stargazing weekend break, 13-15 March 2015, at the Selkirk Arms Hotel, Kirkcudbright, near Galloway Forest Dark Sky Park

Stargazing weekend break and Solar Eclipse Special, 20-22 March 2015, Kirkcudbright, near Galloway Forest Dark Sky Park (this weekend break can be extended to a three night stay to watch the partial eclipse of the sun at sunrise on Friday 20 March!)

Stargazing weekend break, 9-11 October 2015, at the Selkirk Arms Hotel, Kirkcudbright, near Galloway Forest Dark Sky Park

Stargazing weekend break, 4-6 December 2015, at Kirroughtree House Hotel, Newton Stewart, in Galloway Forest Dark Sky Park

Stargazing weekend break, 11-13 December 2015, at Kirroughtree House Hotel, Newton Stewart, in Galloway Forest Dark Sky Park

 

Join me for IndyRef Stargazing on Twitter!

September 16, 2014 3 comments

Join me this Thursday night / Friday morning (18/19 September 2014) for some Twitter-based stargazing!

Coll night sky, some of the darkest skies in Europe

Coll night sky, some of the darkest skies in Europe

Many people will be staying up late or even overnight to watch the results of the Scottish Independence Referendum come in. To while away the wee small hours I thought it’d be fun to do a bit of stargazing too!

If you find yourself staying up late then join in by following me on Twitter @darkskyman, and using the hashtag #indyrefstargazing. I’ll kick things off around 9pm on Thursday as the sky darkens, and throughout the night I’ll be describing what’s up in the sky, and how best to see it, winding up around 6am as the dawn breaks. By then we’ll be eagerly awaiting the result of the referendum, which is estimated to be around 7am.

Join in, it’ll be fun! You can send me questions via Twitter too, or just say hello. You don’t need any equipment to take part: just your eyes and clear skies. If you’ve got binoculars, dig them out, as you’ll be amazed how much more you can see.

Watch a Star Disappear Behind an Asteroid: Wednesday 10 September 2014

September 9, 2014 Leave a comment

Many thanks to the always-excellent Astronomy Now magazine for this story. Their full article is here, and is well worth a read.

In the early hours of the morning of Wednesday 10 September (at around 0306BST) stargazers in the northern part of the British Isles have the chance to witness a star disappearing, if only for a few seconds.

The star in question – HIP 22792 in the constellation of Taurus – is faint, though, and so you won’t see it with your naked eye. The good news is that you can see it through even a modest pair of binoculars mounted on a tripod, and it’s easily seen through a telescope.

So why is it blinking off and on again? In fact it isn’t, but for those few seconds a much smaller but much closer object, an asteroid called (569) Misa will pass in front of it, perfectly obscuring it for observers in a 90km wide band running from Galway in Ireland all the way up to Peterhead near Aberdeen. Observers within this band will see the occultation, and those near the centre line (including me in Glasgow and stargazers in Sligo, Londonderry, and Dundee) will get the best view, with the occultation lasting longest (3.6 seconds!).

The path of occultation. Image from Astronomy Now.

The path of occultation. Image from Astronomy Now.

How to find HIP 22792

The faint star in question is located in the constellation of Taurus, and will be around 38° above the eastern horizon at the time of occultation. Luckily there are plenty of bright stars nearby to signpost you there.

The location of HIP 22792 in Taurus at 0306 Wed 10 September 2014

The location (crosshairs) of HIP 22792 in Taurus at 0306 Wed 10 September 2014

Here’s a close up of the area in question:

The stars around HIP 22792 at 0306 Wednesday 10 September 2014

The stars around HIP 22792 (crosshairs) at 0306 Wednesday 10 September 2014

The stars labelled in red (by me) are the signposts to HIP 22792. Stars a and b (ι Tau and τ Tau) are both naked eye in anything other than bright city light pollution, shining at magnitudes +4.6 and +4.3 respectively. This makes them very easy to spot in binoculars. Draw an imaginary line between a and b and cut it with a perpendicular line moving in the opposite direction from the bright star of Aldebaran, and the next bright-ish star you come to is labelled c, HIP 22743, which shines at +6.5. Continue along this line past a faint star (unlabelled) shining at +7.4, then double that distance again to find the target, HIP 22792, which is the faintest so far, at +7.6. The stars labelled d and e are there for reference, and are at +5.8 and +6.3 respectively.

Practical tips for finding HIP 22792

If you have a telescope with in-built goto and tracking you’re good to go but for the rest of us we need to do a bit of prep.

  • At the very least you’ll need to mount your binoculars on a steady tripod, or have your scope aligned, so that you can track the target for several minutes.
  • Finding it may take some time so don’t just fall out of bed expecting to locate it easily. Give yourself at least 20 minutes of set-up (or more, if you’re new to this!)
  • Make sure you’re observing from a site that has a good eastern view, that isn’t obscured by buildings or trees
  • As always, the further you can get from the glare of street lights the better.

The Great Northern Lights Display of 27 Feb 2014

February 28, 2014 1 comment

Last night, Thursday 27 February 2014, the UK was treated to one of the best displays of Northern Lights in the past twenty years. Twitter erupted with excitement, and then pictures, which my good friend @VirtualAstro and myself @darkskyman RT-ed and commented on throughout the evening.

Aurora over Aberdeenshire, by Mark Tait @marktait78

Aurora over Aberdeenshire, by Mark Tait @marktait78

Below is just a sample of some of the best images that came in last night, but before that let’s look at why this aurora display was so good.

Two days previously a large sunspot on the surface of the Sun erupted with a huge X-class flare, rated at X4.9, the strongest of the year so far. This flare blasted off material from the Sun’s surface in what’s known as a Coronal Mass Ejection (CME). We knew that this material wasn’t aimed straight at us, but last night, two days after the eruption, it sideswiped the Earth, getting caught in our magnetic field and funnelled to the north and south poles.

It just so happened that the angle of the impact, and the timing, was perfect for evening skywatchers across the UK, and with largely clear skies across the country reports started coming in around 7pm that we might be about to see storm level activity. In the end it was rated as G2 (moderate) but the position of the auroral oval meant that even this moderate storm produced some of the best views of aurorae in the UK that I can remember.

Don’t be downhearted if you missed it; there’s a chance (55% according to NOAA) that we might see more tonight as we move through the wake of the CME. It’s unlikely to be as good as last night’s show, but still worth a look.

I tweeted the best way to see the aurora:

Then images started coming in!

This from @garethpaxton in Central Scotland (a pic of the viewfinder of his camera):

Then this beautiful one from Jim Hunter Images in East Lothian:

From @ross1772 in Newmill, Scotland

Dave @makapala uploaded a bunch of images taken from Fife to his Flickr account:

Mark Tait @marktait78 got this amazing image from Aberdeenshire, showing the verticality of the aurora:

England also got some of the action with the aurora stretching as far south as Uttoxeter, in this image by @RichardH082:

And Whitby (from @whitbyglenn)

From Ravenscar (from @andy_exton)

And NE England (via @Astro_Matt27)

Northern Ireland got in on the action too, as this amazing image from Paul Martin shows:

But of course the best of it was in the north of Scotland, such as this stunning image from Innes Mackay in Lewis:

Stargazing Weekend Breaks 2013-14

October 19, 2013 Leave a comment

There’s a great piece in Guardian Travel today about stargazing breaks in and around Galloway Forest Dark Sky Park. The article was written by Kevin Rushby, who visited the park earlier this year, and who I took out stargazing on a beautiful night.

It really is an amazing place, and on a clear winter’s night you can see thousands of stars, the Milky Way, shooting stars, nebula, galaxies, satellites… and much more.

But for most people the night sky is a confusing place, and having a guide to lead you around is an ideal way to begin stargazing. (Ahem! A good guide book is handy too…) I run regular stargazing weekends and evenings at a number of hotels near Galloway Forest Dark Sky Park (and one down in Exmoor!) over the course of the winter. Here are the dates for the weekends I have planned for this coming winter:

1-3 November 2013 Selkirk Arms Hotel, Kirkcudbright
29 November – 1 December 2013 Kirroughtree House Hotel, Newton Stewart (SOLD OUT)
6-8 December 2013 Kirroughtree House Hotel, Newton Stewart
31 January 2013 – 2 February 2014 Yarn Market Hotel, Exmoor
28 February – 1 March 2014 Kirroughtree House Hotel, Newton Stewart
28-30 March 2014 Selkirk Arms Hotel, Kirkcudbright

I also run bespoke stargazing nights at Glenapp Castle, Ballantrae.

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