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| Kessingland Beach, Suffolk. George Roberts 2014 (digital media) |
Friday 21 March 2014
Friday 14 March 2014
The Spectra of Stars
The light from a star can tell professional astronomers much about a star's temperature and chemical composition. The colour alone can provide information as to temperature, the bluer the hotter and the redder the cooler, but it requires spectroscopy to provide information as to the chemical composition.
To obtain a spectrum from light you require a prism or a diffraction grating. A diffraction grating is comprised from a number of fine parallel lines etched on glass or metal. A CD disc can perform as a diffraction grating and if you look at one obliquely you will see the typical colours of the spectrum of white light.
You can purchase diffraction gratings for use with amateur sized telescopes but they cost about £100. I wondered whether I could make one and whilst surfing the internet found a useful programme on the COAA website.
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| Sirius through my eyepiece with spectrum visible in offset spikes |
Well it took me about an hour and I had what looked like a diffraction grating. Would it work?
One of the main problems of obtaining a spectrum from starlight is that the amount of light you can collect is very small.
On the 9th of March, whilst I was awaiting the shadow transit of Jupiter by its moon Ganymede, I decided to try and capture the spectrum of Sirius and that of Betelgeuse. I chose these stars as they are both bright stars and at opposing ends of stellar classification. The following images were taken with a handheld compact camera, held to the telescope eyepiece and using the video setting . I converted the mov. clips to avi format and then stacked the frames to create stills using AutoStakkert.
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| Betelgeuse through my eyepiece with spectrum visible in offset spikes |
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| Spectra of the two stars side by side for comparative purposes using my homemade diffraction grating |
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| The above Spectra cleaned up, enlarged and saturation increased in APS |
These two spectrums can be seen to be quite different, indicating the very disparate temperatures and compositions of the two stars.
All in all I was quite surprised by how well my homemade diffraction grating works. Calibrating my spectra however, remains another issue to which I need to give more thought. Not bad though for an old fine arts graduate!
Dare to be a Daniel
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| Tony Benn 1925-2014 |
The death of Tony Benn was announced today. In his time and amongst many achievements, he had been; MP for Chesterfield, a lifelong committed socialist and a man of intellectual principle. Unknown to him, he was also my mother-in-law's and Toot's political hero!
Tony Benn's political career spans from our childhood to our fast approaching old age and in all that time Toot and I cannot recall a time in which he chose the easy road, he was a man of principle who would not succumb to political expediency or vested interest.
In his memoirs he recalled that his mother challenged him to 'Dare to be a Daniel'. The record of his life bears testament to his complete success in achieving such an exacting objective.
On many issues, the current generation of British Politicians would do well to follow his lead :
"I did not enter the Labour Party 47 years ago to have our manifesto written by Dr Mori, Dr Gallup and Mr Harris" - Tony Benn Newspaper article, 1988.
Lets all try to 'Dare to be a Daniel' and make the world a better place!
http://www.bbc.co.uk/news/uk-politics-18686794
Wednesday 12 March 2014
Double Shadow Transit
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| Jupiter with Io passing in front and above it's clouds and the shadows of both Io and Ganymede creating black discs on the cloud tops |
The images were taken on the 9th March 2014 from our backyard using a QHY 5v planetary camera attached to my 127mm Meade Apo at F 18.75 mounted on a NEQ6. Video clips were stacked using AutoStakkert and finished with APS. Images a bit washed out by moonlight and possibly thin high level cloud. Not totally convinced that image of Io is real or an artifact of using APS but the moon is about in the right place so fingers crossed!
Post Script 20th July 2014: Well the above image of Io turned out to be an artifact of using APS (Photoshop) 'sharpening tool' too aggressively. So where was Io? Well the apparent answer is quite interesting. I spent a bit of time enlarging Ganymede' shadow and realised that there was a possibility that I had taken my photograph at the precise moment Ganymede's shadow was falling upon the planet Io. Io orbits Jupiter much closer than Ganymede and therefore a solar eclipse upon Io caused by an outer moon although unlikely was a real possibility. I believe an eclipse is the answer to my missing moon Io mystery!
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| Enlarged view of Ganymede's shadow. Clearly the shadow is far from circular. I believe the less dense area of shadow (at 2 o clock) is the planet Io emerging from or entering into solar eclipse |
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| Best image processed iteratively in PIPP, AutoStakkert, Registax 6 and APS |
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| This black and white image was taken just before the above colour images |
Tuesday 11 March 2014
One hell of a bang!
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| Taken from our backyard at 11.20pm on the 9th March 2014. 9 x 30 sec lights, 3 darks and 3 flats at ISO 1600, stacked using DeepSkyStacker and finished using APS. 127mm Meade Apo and Canon 600d DSLR . NEQ6 mount unguided |
Messier 82 or NGC 3034 and sometimes referred to as the Cigar Galaxy is some 11.5 million light years distant. A very very long way away but in the context of the distribution of galaxies in the Universe a close neighbour of our own galaxy the Milky Way.
M82 is presented to us almost edge on, hence the cigar shape but has been determined to have two spiral arms which are largely obscured by a complex of dusty filaments. New stars in this galaxy are being created at a prodigious rate, almost ten times faster than in our own galaxy and because of this it is labeled as a 'starburst galaxy'. This star birth activity and the deformation of M82 is caused by the gravitational tidal forces acting as the result of its proximity to the much larger galaxy M81.
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| Messier 82 as imaged by the Hubble Space Telescope taken in 2006 |
In January of this year, Dr Steve Fossey and undergraduate students at the Mill Hill Observatory of University College London discovered a Supernova in M82
See:
http://www.ucl.ac.uk/maps-faculty/maps-news-publication/maps1405
This supernova is considered to be a Type 1A supernova.
A type 1A supernova occurs when a white dwarf star, part of a binary star system, is completely destroyed in a massive nuclear detonation.
See:
http://en.wikipedia.org/wiki/Type_Ia
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| Montage of my own images showing the location of the Supernova |
The size of this detonation and explosion is almost unimaginable. The remoteness of this star is also difficult to grasp. 11.5 million light years is a very long way.
67,604,193,724,356,720,000 miles!
or
108798403545131160000 Kilometres
So when we look through a telescope and it appears as bright as some relatively nearby stars in our galaxy, we know that it represents an enormous release of energy. The intensity of the burst has peaked and is now in decline. Interestingly, the explosion occurred some 11.5 million years ago and the light from it has spent all this time traversing the vast distance between M82 and the Milky Way. The photons I collected in my camera started off 7 million years before we emerged as a species. The Universe really rocks!
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| Enlargement of my image showing the foreground stars in the Milky Way and M82 with the Supernova far away in the distance |
The brightest star in our sky is Sirius, in winter in the UK you can see it shining brightly, below and to the left of the constellation Orion. Sirius is 9 light years distant. If the Supernova had occurred at that distance from Earth it would have had a visual magnitude of -18.7 , a point source of light with an apparent luminosity somewhere between the brightness of the Moon and the Sun.
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| Star map showing position in the night sky of M81 and M82 near the Plough asterism |
Credits: UCL/University of London, Hubble Space Telescope and SkyMap Pro
Friday 7 March 2014
Curiosity update No 1 2014
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| Latest photographs from the Curiosity rover in Gale crater on the surface of Mars |
If you go out after midnight on a clear night in March or April of this year and look between south and southeast a little above the horizon, you will see a new bright pink star in the constellation of Virgo. It is however a planet, not a star, the red planet Mars. In April, Mars will be at opposition, that is at its closest to the Earth.
I hope to take some photographs of Mars through my telescope and if successful I will post them on this blog.
In the meantime I created this collage of images taken from the NASA website.
The top panorama shows the Mastcam view taken by the Mars rover Curiosity as it approached a sand dune which spans 'Dingo Gap' in Gale Crater. The image was recorded on the 28th January 2014.
The bottom panorama shows an outcrop of rocks named 'Junda' which Curiosity passed on February 19. Mount Sharp in the centre of Gale Crater can be seen behind the outcrop.
Centre left is an image taken by Curiosity looking up and over the crater rim. The bright star like point of light shown in this image is in fact our planet Earth. Just below it is a fainter point of light our Moon.
Centre left is an image of rock with crystals clearly visible. The rover is equipped with a range of visualisation and analysis equipment. The crystals are of feldspar in a pyroxene matrix typical of basaltic igneous rocks on Earth. "This texture provides compelling evidence for igneous rocks at Gale Crater".
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| Starmap South March 2014 Midnight |
Credits: NASA /JPL CALTECH MSSS and Starmap Pro.
It's Friday and time to enter the Pizzaroid Belt
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| Toot's Pizzas are out of this world |
"Pizza, the most Italianate of all the cheese on toasts"
William Roberts
Tomato paste, extra virgin olive oil, ripped fresh basil leaves, garlic, pecan nuts, gorgonzola cheese, smoked oysters and optional broccoli on a thin and crispy homemade sourdough base - Mmmm stuffed crust!
Credits: JPL NASA and Toot's Kitchen
Tuesday 4 March 2014
Over the Boardwalk down by the Sea.
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| Reeds and dragonflies (mixed media George Roberts March 2014) |
Short lives
On Hatshepsut’s land
In the past
Not so long ago
We watched a boy fly upon a thread
An African bee
A fearsome kite complete with sting.
In Suffolk reeds
Two summers past
Not so long ago
We watched a dragonfly upon a breeze
A sapphire insect
A complete life but fearsome brief
George Roberts
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