Mar 20 2015

…when the sun is eclipsed by the moon

Friday 20th March 2015 saw a solar eclipse visible over the British Isles, subject to the vagaries of the British weather. I have some form in taking pictures of the sun through my telescope. With solar eclipses taking place in the UK only once every 10 or so years (the last one was in 1999), I thought it worth the effort to take some pictures.

The key piece of equipment was the Baader AstroSolar filter mount I made a while back. It’s designed to fit on my telescope but works pretty well for naked-eye viewing and with my Canon 600D camera. I used a Canon 70-300m lens, mainly at the maximum zoom with varying exposure parameters depending on cloud. I used autofocus in the main but manually set exposure time, aperture and ISO. Consumer cameras aren’t designed to give good auto exposure for usual activities such as eclipse observations.

Here’s a closeup of the filter:

solarfilter

The uninitiated may not be impressed by the finish on this piece of equipment but as a scientist of 20 years standing I’m happy to report that I’ve had plenty of stuff in my lab in similar style – it’s good enough to do the job.

Solar eclipses last a surprisingly long time, this one was a little over two hours with first contact of the moon on the suns disk at 8:26am in Chester. This photo was taken at 8:26am, you can just see the moon clipping the edge of the sun top right.

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By 9:01am things were well under way. The birds had started their evening song around this time and it was starting to feel unusually dark for the time of day.

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The maximum of the eclipse was at 09:30am, by this time clouds had appeared and I used them as an ad hoc solar filter.

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By 09:50am we were well past the maximum:

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The last photo I managed was at 10:18 before the sun disappeared behind the clouds:

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Finally, this is a collage of the majority of pictures I took – some of them are pretty rough:

010 - Eclipse - 20mar151

Nov 15 2014

Landing on a comet

There was a striking contrast in the office on Friday between the former practicing scientists and the developers, with an open data background, who were bemoaning the slowness with which results were being reported by the ESA team looking after the Rosetta orbiter and the Philae lander.

As I pointed out, many years ago I sat in an instrument hutch at the Rutherford Appleton Laboratory trying to work out what the hell was going on with my experiment downstairs, behind an interlocked door, being flooded with a beam of invisible neutrons. It was possible that I was discovering new and important science. But on the other hand it was also possible that the goniometer third from the left on my sample changer was up to its usual tricks and had failed to move when instructed. We couldn’t tell from the frankly inadequate early nineties video feed. The only way to find out was to wait for the experiment to finish and go and eyeball the damn thing.

Goniometer number 3 had failed, again.

Peter, who did his PhD at CERN, replied – “what he said!”

Feb 26 2014

Messier and messier

Regular readers with a good memory will recall I bought a telescope about 18 months ago. I bemoaned the fact that I bought it in late Spring, since it meant it got dark rather late. I will note here that astronomy is generally incompatible with a small child who might wake you up in the middle of the night, requiring attention and early nights.

Since then I’ve taken pictures of the sun, the moon, Jupiter, Saturn and as a side project I also took wide angle photos of the Milky Way and star trails (telescope not required). Each of these bought their own challenges, and awe. The sun because it’s surprisingly difficult to find the thing in you view finder with the serious filter required to stop you blinding yourself when you do find it. The moon because it’s just beautiful and fills the field of view, rippling through the “seeing” or thermal turbulence of the atmosphere. Jupiter because of it’s Galilean moons, first observed by Galileo in 1610. Saturn because of it’s tiny ears, I saw Saturn on my first night of proper viewing. As the tiny image of Saturn floated across my field of view I was hopping up and down with excitement like a child.

I’ve had a bit of a hiatus in the astrophotography over the past year but I’m ready to get back into it.

My next targets for astrophotography are the Deep Sky Objects (DSOs), these are largish faint things as opposed to planets which are smallish bright things. My accidental wide-angle photos clued me into the possibilities here. I’d been trying to photograph constellations, which turn out to be a bit dull, at the end of the session I put the sensitivity of my camera right up and increased the exposure time and suddenly the Milky Way appeared! Even in rural Wales it was only just visible to the naked eye.

Now I’m keen to explore more of these faint objects. The place to start is the Messier Catolog of objects. This was compiled by Charles Messier and Pierre Méchain in the latter half of the 18th century. You may recognise the name Méchain, he was one of the two French men who surveyed France on the cusp of the Revolution to define a value for the meter. Ken Alder’s book The Measure of All Things, describes their adventures.

Messier and Mechain weren’t interested in the deep sky objects, they were interested in comets and compiled the list in order not to be distracted from their studies by other non-comety objects. The list is comprised of star clusters, nebula and galaxies. I must admit to being a bit dismissive of star clusters. The Messier list is by no means exhaustive, observations were all made in France with a small telescope so there are no objects from the Southern skies. But they are ideal for amateur astronomers in the Northern hemisphere since the high tech, professional telescope of the 18th century is matched by the consumer telescope of the 21st.

I’ve know of the Messier objects since I was a child but I have no intuition as to where they are, how bright and how big they are. So to get me started I found some numbers and made some plots.

The first plot shows where the objects are in the sky. They are labelled, somewhat fitfully with their Messier number and common name. Their locations are shown by declination, how far away from the celestial equator an object is, towards the North Pole and right ascension, how far around it is along a line of celestial latitude. I’ve added the moon to the plot in a fixed position close to the top left. As you can see the majority of the objects are North of the celestial equator. The size of the symbols indicates the relative size of the objects. The moon is shown to the same scale and we can see that a number of the objects are larger than the moon, these are often star clusters but galaxies such as Andromeda – the big purple blob on the right and the Triangulum Galaxy are also bigger than the moon. As is the Orion nebula.

Position

So why aren’t we as familiar with these objects as we are with the moon. The second plot shows how bright the Messier objects are and their size. The horizontal axis shows their apparent size – it’s a linear scale so that an object twice as far from the vertical axis is twice as big. Note that these are apparent sizes, some things appear larger than others because they are closer. The Messier The vertical axis shows the apparent brightness, in astronomy brightness is measured in units of “magnitude” which is a logarithmic scale. This means that although the sun is roughly magnitude –26 and the moon is roughly magnitude –13, the sun is 10,000 times bright than the moon. The Messier objects are all much dimmer than Venus, Jupiter and Mercury and generally dimmer than Saturn.

Size-Magnitude

  

So the Messier objects are often bigger but dimmer than things I have already photographed. But wait, the moon fills the field of view of my telescope. And not only that my telescope has an aperture of f/10 – a measure of it’s light gathering power. This is actually rather “slow” for a camera lens, my “fastest” lens is f/1.4 which represents a 50 fold larger light gathering power.

For these two reasons I have ordered a new lens for my camera, a Samyang 500mm f/6.3 this is going to give me a bigger field of view than my telescope which has a focal length of 1250mm. And also more light gathering power – my new lens should have more than double the light gathering power!

Watch this space for the results of my new purchase!

Nov 10 2012

By Jupiter!

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Jupiter (From video acquired on Celestron NexStar 5SE, Baader Hyperion zoom eyepiece at 8mm,Canon 600D, 1/30s at ISO800 stacked in Registax6)

This morning I managed some photos of Jupiter through the telescope, a Celestron NexStar 5SE.

This was helped with my latest purchase: a Baader Hyperion 8mm-24mm zoom eyepiece – this gives me more magnification and allows me to attach to my Canon 600D camera via a couple of mounting rings (here and here). Previously I could only get low magnification on my camera, or high magnification via a 3x Barlow lens.

The Baader-Hyperion is a nice bit of kit, instructions are minimal though so working out how to attach the camera was a case of twisting various bits of the eyepiece to find out what unscrewed – I did this in the light a couple of days ago. The only small problem is that once the camera is attached to the eyepiece it rotates when the zoom level is changed.

I left out the Star Diagonal for these images, this is Celestron’s right angle bending device which gives better naked eye viewing because you can look through the eyepiece from the standing position rather than crawling around on the floor. However, it does seem to introduce some chromatic aberration. The Canon 600D has a rotatable LCD which gives a reasonable viewing position even without the Star Diagonal.

I had a rather disappointing try at Jupiter a few days ago, disappointing because the night started clear but had clouded over almost completely by the time I got my telescope out; then the neighbours started letting off fireworks; then I couldn’t remember how to work my camera in the dark and then it started raining! On top of all that my Baader Hyperion eyepiece hadn’t turned up.

The useful thing I got out of the evening was a fair idea of appropriate ISO number and exposure times to use – Jupiter is surprisingly bright and needs something like ISO800 at 1/50s on my ‘scope, even at high magnification.

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Jupiter, single image Celestron NexStar 5SE, Baader Hyperion zoom eyepiece at 8mm, Canon 600D, 1/50s at ISO800

Jupiter was one of Galileo’s first targets for his telescope in the early 17th century, importantly he observed the four brightest Jovian moons (Callisto, Io, Europe and Ganymede). Significant because they orbited Jupiter, not the sun or the earth and they changed from night to night – at the time the stars were supposed to be immutable and rotate around the earth, or at least the Sun.

You can see these in two photos I took, on 5th and 10th November – the moons have moved quite obviously.

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Jupiter and moons on 5th November at 8pm (Celestron NexStar 5SE, 1/4s at ISO6400)

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Jupiter and moons on 10th November at 5am (Celestron NexStar 5SE, Baader Hyperion zoom eyepiece at 16mm?, 1/50s at ISO6400)

Actually, it’s not quite that simple: the photo from the 5th was taken in the early evening with Jupiter in the east whilst that on the 10th was taken in the early morning with Jupiter in the west. Jupiter appears to move between these two locations because of the earth’s rotation and this also means the orientation changes. Not only this, my telescope was configured differently on the two occasions: the Star Diagonal + camera combo flips the image vertically whilst the direct eyepiece view flips both horizontally and vertically. I’ve rectified the images appropriately, and labelled them following Stellarium.

I also took some video on the 600D. You can see it here, the juddering at the beginning and end is the result of me poking buttons on the camera. The rippling of the image is the “seeing”, it’s caused by the atmosphere. The point of taking video is that it can be used to mitigate the effect “seeing” by averaging frames, I did this using Registax 6 but first I had to convert the video from Quicktime to avi format using ffmpeg:

ffmpeg –i filename.mov –sameq filename.avi

ffmpeg can do anything with video, if you give it the right incantation, in this case it recognises that I want to convert an input video from mov (Quicktime) format to avi format, the –sameq flag tells it not to drop the quality of the video as it does so.

I have to admit to not really knowing how to use Registax, I simply let it do its default thing and the result looked okay:

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Jupiter (From video acquired on Celestron NexStar 5SE, Baader Hyperion zoom eyepiece at 8mm,Canon 600D, 1/30s at ISO800 stacked in Registax6)

A fun half hour of imaging, I’d have moved on to another target if I’d planned ahead. The earlier, unsuccessful imaging session was helpful in getting me close to the right camera settings and spurring me to learn how to learn how to use the camera in the dark. The Baader Hyperion eyepiece is rather nice!

Aug 05 2012

My letter to Sir David Attenborough…

It seems Sir David Attenborough doesn’t think he has influenced people to take up science, some people have organised a letter writing to show how wrong he is, see here on how to contribute: http://dearsirdavid.wordpress.com/submission/

This is my contribution:

Dear Sir David,

I’m a scientist. I did a degree in Chemical Physics at Bristol University, a PhD in Polymer Physical Chemistry at Durham University and I became a lecturer in Biological Physics at UMIST, I still work as a scientist.

 

I understand you may not realise how many people you have inspired to become scientists, so I’m writing to say: you inspired me! As a child I was interested in the natural world; “Life on Earth” came along when I was nine years old. It was a grand story, it did not just cover the cute and fluffy animals, it went to Australia to look at the stromatolites. I went on to study the physical sciences formally but  to me science is all one big story and you helped make that clear to me.

 

I eagerly awaited each new series you made, I still do, because they don’t insult my intelligence and I come away learning something new. Your recent First Life series is a fine example, I read about the Burgess Shale long ago but you visited those bleak places where the evidence of the first life on earth were found; were passionate about the un-imposing smears they left on the rock and told the story. I never knew trilobites had calcite eyes.

 

You can claim some matchmaking credit too: were it not for “Life on Earth”, my wife would not have attended Bristol University to do a degree and we would never have met!

 

You still inspire me because at an age where I might reasonably expect to be retired, you are being hoisted up trees, dropped on atolls by helicopter, and standing on mountains of bat dung.

 

Thank you, Sir David!

 

best regards

 

Dr Ian Hopkinson

 

I have to say I was welling up when I wrote this…

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