The evening started clear but clouded over just as me and few other friends from NASTRO were arriving at Hauxley Nature Reserve.  I got polar aligned with the 80mm refractor through occasional gaps in the cloud so that when the sky did begin to clear at around 8.30pm I was able to find the asteroid fairly quickly.

A point of light drifting through the stars in the eyepiece.  It was easily discernible motion at low magnification.  I put the camera in place and took this one minute exposure:

The moving asteroid shows up as a line because of the long exposure.  Then the clouds returned so I felt very happy to have seen anything at all!

2012DA14 ranks as one of the closest astronomical objects I’ve taken pictures of….only spaceweather like the aurora, noctilucent clouds or ISS are closer.  Later that evening I had a go at imaging something much more distant….in fact, it’s the furthest object I’ve ever tried to take a picture of!  Here it is:

It looks like a star but is really a quasar (and that’s why these objects were initially named Quasi-Stellar Objects) but it is actually the active nucleus of a very distant galaxy.  3C-273 is a mind crushing 2.4 billion light-years away in the constellation Virgo.  That’s about 1,000 times further away than the Andromeda Galaxy.  This quasar is the brightest in the entire sky and one of the nearest to us.  Quasars were more prevalent in the early universe and are an indication how violent the processes at work in the centres of galaxies can be!  Material is falling into a supermassive blackhole and getting shredded and heated in the surrounding accretion disk.  The energy released, in the form of light and other radiation is beamed outwards and we happen to be looking down the beam. Rather like seeing a lighthouse beam sweeping past us.

Checking on my astronomy software…I noticed that another asteroid, called Hera, was also in the frame.  Hera is a foreground object – just under 200 million miles away in the asteroid belt between Mars and Jupiter.

Prior to closest approach 2012 DA14 will be best seen from the southern hemisphere.  The orbit brings the asteroid towards us from beneath the south pole of the planet.  2012 DA14 is expected to be at its closest to Earth – just 27,700 km (17,200 miles) above the surface – at 1924UT (7.26pm GMT).

There is no danger of a collision with the Earth or any satellites.  But amateur astronomers around the world will be trying to catch a glimpse of this rocky visitor near the time of its closest approach.  I’m one of those astronomers hoping for a clear sky on Friday evening so I’ve spent a bit of time preparing myself for the event.

I’m going to try to view the asteroid from Northumberland and at the moment of close approach 2012 DA14 will be below the horizon.  But it is moving very rapidly through the sky and will rise above the horizon in Northumberland at about 25 minutes later.

Here is a chart generated with SkyTools 3 showing the path of 2012 DA14 after it rises in Northumberland on the evening of Friday February 15th.  Note that the times given in the following star charts may be in error by several minutes – the orbit of the asteroid is not precisely determined enough to make timings without giving that caveat.

To observe the asteroid I’m going to use a small telescope – an 80mm refractor – and choose a part of the sky that I know the asteroid will pass through.  I’ll start looking about 15 minutes before the asteroid is due to arrive at that spot.

The asteroid, predicted to have a brightness of around 7th magnitude at 8pm (just visible with binoculars) will be in the constellation Virgo, close to the border with Leo.  From Hauxley, it probably won’t be possible to see it until it is good altitude above the horizon.  I think I’ll be able to pick it up visually with the 80mm telescope at about 8.20pm as it cruises past the large scattering of stars in Coma Berenices called Collinder 256.  At that time, the asteroid will be tracking across the sky at 37 arcseconds per second.  In other words, it will cover a distance in the sky just smaller than the size of Jupiter every second.  Definitely detectable against the background stars.

By 8.40pm the asteroid will be passing the constellation Canes Venatici – just beneath the familiar seven stars of The Plough.  Larger telescopes will see it tumble past the Silver Needle galaxy (NGC4244) – an edgeways on spiral galaxy glowing at 10th magnitude.  At 9.04pm the asteroid passes close to another galaxy in Canes Venatici;  M106 is a spiral galaxy whose elongated glow will be visible with medium sized telescopes fairly easily.  By this time the asteroid will be shining at 9th magnitude and fading as it recedes from Earth.

After 9.15pm the asteroid is seen against the familiar backdrop of The Plough – probably the most recognisable pattern of stars in our northern sky.  The chart below shows the trajectory of asteroid during a 45 minute period when it should be easier for novice astronomers to locate.

At 9.34pm the asteroid passes between two bright stars of The Plough – Alioth and Phad.  This might be the easiest opportunity for inexperienced astronomers to find the asteroid with a telescope.  Although dimmer by a factor of 2 compared to closest approach, it will be much easier to detect with UK based telescopes because it is much higher in the eastern sky.

By 10pm the asteroid is shining at 10th magnitude and travelling across the sky just one-third as fast as it was a couple of hours earlier.    While it remains an easy target for larger telescopes it will continue to slow (relative to the background sky) and fade.  The final chart shows 2012 DA14 as it heads towards Polaris and the north celestial pole of the sky during the early hours of the 16th.

Here’s hoping for clear skies, no technical problems with the ‘scope and a hot pizza on a cold night!

The orbit of the comet around the Sun is tilted to more than 90 degrees to the plane of the Earth’s orbit.  This basically means that K5 LINEAR is moving from celestial north to south in the sky.  The following chart shows the rapid motion of the comet during the next week or so.

K5 LINEAR is tracking south through a busy region between the constellations Orion and Taurus.  I set up the 80mm Skywatcher refractor on the HEQ5 Pro mount without much hope of getting a great picture.  It was overcast and raining at one point so me and Malcolm had to throw a cover over the whole setup.  But the cloud was quick moving and eventually I got a clear spell lasting more than half an hour.

This image is a composite of 10 one-minute subexposures taken with the Nikon D80 at prime focus of the Skywatcher telescope.  The processing was carried out in DeepSky Stacker and GIMP.

The green colour of the comet is from jets spewing cyanogen (CN) and diatomic carbon (C₂) into space.  Both have a distinctive green glow under the action of sunlight in space.

The sub-exposures actually show the rapid motion of the comet across the field of view.  Here is an animation showing the comet as it tracks across the sky at a rate of 10 arcseconds per minute.

K5 was about 0.3 astronomical units away (about 28 million miles) when the pictures were taken.  That rapid motion corresponds to an orbital speed of about 80,000 miles per hour!  (Since the comet is passing through the plane of our orbit, the radial component is almost zero).

Comet K5 LINEAR is already fading as it heads south and away from the Sun.  But 2013 looks like it will be a spectacular year for other comets!  In late February we’ll have a naked eye comet called PANSTARRS in our sky and towards the end of the year – a more dramatic visitor called ISON might give the moon a good run for it’s money.

]]> https://cosmicriver.wordpress.com/2013/01/07/capturing-a-comet/feed/ 0 jannetta3008 LINEAR_Finder C2012K5Linear_050113 https://cosmicriver.wordpress.com/2012/08/01/blue-moon/ https://cosmicriver.wordpress.com/2012/08/01/blue-moon/#comments Wed, 01 Aug 2012 23:43:56 +0000 http://cosmicriver.wordpress.com/?p=662 ]]>

It’s August 2nd and there’s a full moon in the sky!

That’s an old picture; unfortunately it’s raining so I can’t see the moon right now.  Fortunately, this month we get two full moons, instead of the usual one!

The time between two successive full moons is about 29.5 days – give or take a little.  This means that in most calendar months there can only be one full moon.  However, if a full moon falls within the first day or two of the month then it’s possible for another full moon to fall before the end of the same month.

That’s exactly what’s happening in August; there will be full moons on August 2nd and 31st.  The second full moon on the 31st is called a blue moon…

In the 19^th century the Maine Farmer’s Almanac divided the year into quarters and listed the dates of the full moons.  Obviously, the full moon provided much needed illumination for farmers after sunset so they were important.  Normally there’d be three full moons in each quarter of the year, but occasionally there is an extra full moon would fall in a quarter.  Farmers always called the final moon of the quarter the “late moon” and so the third full moon was deemed to be the extra one; they called it a blue moon.  In many cultures the usual pattern of monthly full moons had names like “Grain moon” (August) or “Harvest moon” (September).  The extra full moon which infrequently appeared in the calendar was known as a “betrayer” moon or a blue moon.  The phrase “once in a blue moon”…well, perhaps it’s from this phenomenon.  They aren’t actually that rare; blue moons will occur once every two and half years on average.

One final note; the term blue moon doesn’t refer to the actual colour of the moon.  The moon usually looks white, yellow or orange-red depending on how high it is in the sky (because of how much air the moonlight has to pass through).  However, volcanic eruptions or forest fires can inject just the right size of dust particle into the atmosphere to give the moon (and Sun) a bluish cast.  These kinds of events are also comparatively rare, happening perhaps less often than a blue moon!

The Moon

The principal phases of the moon this month are:

The Planets

Mercury is an evening sky object and it reaches greatest elongation east of the Sun on July 1st at 26°E.  However, it sets shortly after sunset so is not likely to be seen by UK astronomers.

Venus is a brilliant object, at magnitude -4.5, in the morning sky among the stars of Taurus.  During the first week of July it lies not far from Jupiter and the Hyades star cluster.  Telescopes show Venus to be a waxing crescent and the angular diameter is decreasing as the planet recedes from Earth.

Looking northeast on July 7th at 3.10am. Aldebaran, Venus, Jupiter and the Pleiades make an almost perfect line in the sky.

Earth is at aphelion – the furthest distance from the Sun of the year – on July 5^th.  The distance between our planet and the Sun will be just over 94½ million miles that day.

Mars is an evening sky object in the constellation Virgo.  The Red Planet is a fading first magnitude star and it is visible low in the western sky for a few hours after twilight has fallen.  Mars is now so distant that high magnifications on well collimated telescopes will be required to see the gibbous disk of the planet.

Jupiter is shining at magnitude -2.1 in the morning sky before dawn.  It will rise a little earlier each successive morning.  Look for Jupiter near the northeast horizon near the more brilliant Venus.  On the morning of July 15th the Moon will pass very close to Jupiter.  From the south of England the moon will graze [PDF] or completely cover the distant planet.  From Northumberland we’ll get the kind of view shown below.

Crescent moon and Jupiter at 3.10am on July 15th as seen from Northumberland.

Saturn is visible in the evening sky, in the west, for a few hours after dark.  Saturn is marginally brighter than Mars, also in the constellation Virgo.  Saturn is to be found 5 degrees north of Spica, the brightest star in Virgo and about the same magnitude as Saturn.

Uranus and Neptune are best seen in the morning sky.  Uranus shines like a star of magnitude +5.8 in the constellation Pisces.  From exceptionally dark skies Uranus is a naked eye object for keen sighted observers.  Binoculars will show it easily enough.  Neptune resides in the constellation Aquarius and telescopes are required to see this 8th magnitude planet.  The positions of both worlds are shown in the chart below:

Positions of Uranus and Neptune at 2am on July 15th 2012.

As an experiment I took a series of images – 30 in all – covering about 6 minutes in realtime and stitched them into a short animation.  Here is the result:

I wanted to get more pictures but (a) it was a work night and (b) a strange animal kept running at me from the darkness and it seemed to be getting braver with each attempt…

The last thing you’d expect on a day like this is to be setting up the telescope to grab some images.  By 8pm the Sun was beginning to peek through the clouds.  I abandoned the Italy-Germany match and got set up in the bedroom because the Sun was too low to see from the garden.

Here is the view in Hydrogen Alpha:

The Sun has been almost blank in white-light in recent days – barely a sunspot to shake a stick at.  That’s all changed now as the next image shows:

Now it’s getting dark and the sky is completely clear.  Now what….bed or noctilucent cloud hunting?  The night is still young and the camera battery is charged.

My best yet!  This was made possible by an interesting discovery about my Nikon camera.  The pictures I’ve been taking prior to this have been careful not to saturate the chip – typically using exposures of about 1/100s at ISO200.

Yesterday I tried to do some longer exposures to try and extract more signal from those prominences around the limb at the cost of overexposing the disk.  The PST only allows a specific colour of red light through to the camera so I was expecting to see a washed out red disk with more obvious prominences.  I began taking pictures with exposure times ranging from 1/20 to 1/5 of a second.

What I actually recorded was a glowing orange ball similar to the final image above!  How can you get orange when the only colour available is red?

The camera chip is an array of red, green and blue sensors.  At fast exposures those photons of red light were activating the red sensors on the chip.  At slower shutter speeds the red sensors become saturated and the signal leaked into the green sensors.  A lot of red plus a dash of green equals orange in this situation.

Splitting the raw image into its RGB components gives this:

 The “B” component was a black image – nothing had leaked into that channel.  The green channel contained a nicely exposed image of the disk, with all the detail around the edge contained in the red channel.  Presumably with an even longer exposure the signal may have leaked into the blue channel as well!  From what I can tell, the green channel contains a higher quality image than the equivalent red channel – it certainly seemed to stand up to the contrast enhancement and sharpening process that followed.

]]> https://cosmicriver.wordpress.com/2012/06/20/red-and-green-makes-orange-solar-imaging-again/feed/ 1 jannetta3008 Sol_Ha_19062012 Sol_RG https://cosmicriver.wordpress.com/2012/06/18/happy-days/ https://cosmicriver.wordpress.com/2012/06/18/happy-days/#respond Mon, 18 Jun 2012 10:16:40 +0000 http://cosmicriver.wordpress.com/?p=604 ]]> The summer solstice (for us northerners) approaches and I’m happy for two reasons.  Firstly, the solstice marks the start of a period when days begin to shorten and I can get back to doing some astronomy at a reasonable hour of the night.  My second reason to be cheerful is that I’ve got a solar telescope to play with until that happens.  Never again will you spoil my fun Earth’s axial tilt!

I found a great page on the Sky & Telescope website with tips for processing these images and I think it paid off with this one.  In particular I corrected the non-uniform illumination which seems to afflict these early images.  Also, I think I’ll try and blend the disk image and ‘edge’ image a bit more smoothly next time.

]]> https://cosmicriver.wordpress.com/2012/06/17/ten-minutes-of-sun/feed/ 1 jannetta3008 Sun_Ha_17062012