I cropped this from the image above. A couple of things to notice: the pink/orange object is called NGC 604 and is a glowing cloud of hydrogen heated by a great cluster of hot stars at its centre. It is the same kind of object as the Orion Nebula but 40 times the size!
Note the graininess of the image; the telescope has resolved the brightest of the giant stars in the galaxy from a distance of 3 million light-years.
A long time since my last blog post! Busy at work, at home and studying. To calm my nerves I've been processing pictures of little bits of the heavens. Not my own images - the summer night sky is getting too bright - but data collected by various sky surveys and available online through the ESO Online Digitized Sky Survey.
A number of surveys are available and offer various degrees of sky coverage; from 45% of the sky (in blue filtered light) to 99% (in red and infrared). The web interface allows selection of a target or specific coordinates. The images can be displayed as a GIF or downloaded as GIF or FITS. The FITS file format contains a wider range of pixel intensities than GIF. I use FITS Liberator to select the best "window" to view the FITS data.
The images are scans of photographic plates taken by some very big telescopes. Many of them were obtained with the 1.2 metre UK Schmidt Telescope in Australia during the early 90s. Being scanned from the original plates means there are some interesting blemishes in some of the plates. Hairs, fingerprints and other defects can be found if you look carefully enough :-) They can, of course be photoshopped out these days!
Here is what typical GIF images look like:
There are subtle differences to the images; the blue filtered image shows the structure in the spiral arms more easily because of the hot (bluish), young stars there. The red filtered image shows the background glow of the disk - containing many more low mass, cooler (redder) stars.
These are grayscale images. To make a natural colour image we'd need an image taken with a green filter! However, no images in green were taken.
Just for fun...I wanted to see some colour images so I synthesised my own green image. This was done by averaging the pixel intensities in the red and blue images. For example, if a pixel is very bright in blue (say a value of 3000) and dimmer in red (say, 1000) then the I'd interpolate the green value to be (3000+1000)/2 = 2000. Doing this for every pixel generates a synthetic green image.
Armed with the red-green-blue (RGB) images it's a simple matter to blend the images to get a colour image:
The full res version can be viewed here. And you really should look at it! The amount of detail in the images is breathtaking.
So this has become my most recent astronomical diversion. You can see some of my other results on Flickr.
Algol, also known as Beta Persei, is an eclipsing binary star in the constellation Perseus. The name derives from an Arabic word meaning "ghoul" and into English as Demon Star!
Every 2.87 days Algol drops in brightness from magnitude +2.1 to +3.4. This variability was discovered in 1782 by the English astronomer John Goodricke. The large, bright primary star is partially eclipsed by a smaller, fainter companion and the eclipses last around 10 hours. Eclipse times are widely available online.
I've wanted to capture a pair of images Algol eclipsed and uneclipsed for a long time. I happened to wander outside a couple of days ago and noticed that Algol was at, or near, minimum brightness. There's a star next to Algol in the sky (rho Per) which makes comparison easy: Algol is usually much the brighter of the two, but during eclipse they shine at roughly equal brightness.
I took a 30 second exposure (ISO3200, 18mm) on the camera at around 10.30pm on September 29th; this was a couple of hours after the middle of the eclipse. The following night I was able to take another picture with the same camera settings. Here are the two images.
The pictures were taken late evening but the camera position was slightly different and the position in the sky was slightly different. I cropped out similar sized areas around Algol and used the software Iris to align the images:
Zooming in on Algol (the bright star on the left in each picture) you can see how it varies in brightness compared to the bright star on the right (rho Persei, which is itself and variable star but over much longer periods than Algol). The stars are slightly sausage shaped because they trailed during the 30s exposure. The images haven't been enhanced or retouched in any way!
Finally....a GIF to compare the variation in brightness:
Possibly in the future I'll do some guided exposures with the CCD and attempt some photometry on images captured during the 10 hour eclipses.
Comet Catalina is currently well placed for UK observers wishing to see it. The comet is tracking north in the sky and over the next week it will bypass the familiar seven stars of The Plough.
An interesting photographic opportunity occurs on the night of January 16th (going into the early hours of the 17th) when the comet will be close to the celebrated double star Mizar (and Alcor) and a bright-ish galaxy called M101 (the Pinwheel).
The picture above is a Stellarium rendition of Mizar, Comet Catalina and the Pinwheel Galaxy. This is the late evening of January 16th. But given that the moon is above the horizon until just after midnight, best views (and pictures) will be obtained during the early hours of the 17th. This is a wide field of view, so I'll try to capture this with the Nikon D80 mounted directly onto my HEQ5 Pro mount; I think shooting at 200mm will frame the region nicely!
I'm about 7 weeks into a distance learning MSc in astrophysics with LJMU. Over the past two weeks the topic being covered was the interstellar medium (ISM) - the vast regions filled with gas and dust between the stars throughout the Milky Way.
During this time the weather has been mostly awful! But there have been a couple of clear nights and during those I've finally been able to try a modified DSLR on loan from a friend to get some images nebulae that are beyond the reach of my normal DSLR.
Here are two pictures taken by stacking dozens of images together. Both were captured through an 80mm refractor.
These nebulae are created when radiation from a hot, young star ionises neutral hydrogen nearby. When the electrons recombine with the hydrogen a very particular photon (corresponding to red light) is emitted. If the star was surrounded by a uniformly dense hydrogen cloud then the resulting nebula would be spherical, with the boundary of the nebula being the place where ionisations and recombinations balance. That's nearly the case for NGC280 above! But hydrogen clouds aren't necessarily distributed so perfectly around stars. In the picture of NGC1499 the nebula is created by the bright star near the bottom of the picture. The hydrogen cloud is clearly some distance from the star.
Hydrogen exists in several forms throughout the Milky Way. Clouds of hydrogen atoms are called HI (H-one!) regions. These ionised nebulae are called HII regions (not to be confused with H2 regions of molecular hydrogen).
I always enjoy getting pictures of these fantastic objects but the astrophysics course is adding a new layer of appreciation to what I'm doing.
Astronomers can get a lot of information about stars and galaxies not just by looking at the light coming from them but by "listening" to them as well. In the 20th century astronomers began building radio telescopes in order to tune into the signals coming from distant objects like pulsars (extremely compact stars spinning very quickly and beaming out radio signals) and galaxies. Giant dishes were built all over the world; in the UK the radio telescope at Joddrell Bank is probably the most famous example.
The signals collected by radio astronomers can be assembled into an image: a radio-map showing where powerful and energetic processes are taking place in the object being studied.
The images collected by radio telescopes suffer from blurring and distortion just as images taken with ordinary optical telescopes do. During the 1960s and 1970s astronomers and mathematicians came up with impressive techniques to improve the quality of the images so that more detail could be extracted and perhaps saving the cost of getting better pictures by building a bigger and better telescope. When digital imaging evolved in the 1980s and 1990s ordinary backyard astronomers with smaller telescopes were looking to get more out of their pictures too. For example, one of the tricks employed is to take lots of images of an object and then use a computer to combine them to get a better picture.
Medical radiography is the process by which the internal structures of the human body can be imaged using a source of x-ray radiation. The problems faced by radiographers taking x-ray images are similar to those encountered by astronomers looking deep into the universe. However, where an astronomer might take lots of images of a galaxy and then combine them together to give a better final image, a radiographer can’t do the same. Repeatedly exposing a patient to x-rays to get a better picture is not an option; a good picture has to be taken first time and using the lowest radiation dose possible. Radiographers have to walk a fine line to do this. Too much radiation is bad for the patient (but the x-ray image will be good) and although less radiation is preferable, the image quality will be poorer. The radiographers are also constrained by the x-ray machines themselves. Producing x-rays puts an enormous heat load on the machine components and so the exposure time must not be too long. This could be avoided by illuminating the patient using a larger x-ray source - but that would blur the image to an unacceptable level.
In applications such as mammography, radiographers are typically trying to see tiny microcalcifications less than one tenth of a millimetre in size. Microcalcifications can be often be benign or they can sometimes be the first sign of a process leading to breast cancer; x-ray images need to be as clear and sharp as possible to see microcalcifications. The images produced by radiographers come after a careful balance of factors relating to patient safety and image quality, but even so, some blurring remains.
It's almost ten years since my PhD at Northumbria University ended. For the best part of four years I'd been involved in studying the problems of image quality that I’ve described. The Regional Medical Physics Group at Newcastle General Hospital allowed me to take x-ray images of test objects using a decommissioned machine. I was able to adapt and apply some of the image processing techniques used by radio astronomers to improve x-ray images and make microcalcifications easier to spot. I also showed that the radiation dose to the patient could be reduced without sacrificing image quality.
Having studied image processing techniques I still use sometimes use them on my own pictures of the Moon and planets taken through my telescope with a digital camera. It's s also gratifying to see that the same mathematics can be used to solve problems connected with seeing distant astronomical phenomena as well ash the very small components of our own bodies.
Not too many clear nights this month but enough to get some pictures of Comet 2014 E2 Jacques. The comet is well placed for UK observers but doesn't look that impressive through small telescopes. It's great that such an unimpressive comet is attracting media attention ;-)
Comet Jacques is moving rapidly across the sky. The problem with taking pictures is that I've been limited to exposures of just 2 minutes through the DSLR on the telescopes. More than that and the comet smears across the image. The middle picture above was an attempt to autoguide on the comet - forcing the telescope to track the motion of the comet rather than the stars. Unfortunately the weather wasn't good that evening but the method worked.
The movie above was compiled from 29 two minute exposures collected on the evening of August 28th. The rapid motion of the comet makes a nice (if short) movie. Comet Jacques was moving at about 37 km/s and was about 84 million km from Earth. It was shining at around 7th magnitude.
I'm hoping for a clear sky tomorrow as Comet Jacques sails past the Garnet Star in Cepheus. Should make a nice photo with contrasting colours.
Just in from a short imaging session in the back garden. This a picture of the star cluster M41 in Canis Major --- just to the south of Sirius, the brightest star in the night sky.
M41 is one of the brighter star clusters in the night sky, shining at magnitude +5.0 and its 100 or so stars are scattered over an area larger than the full moon.
Viewed from the UK the cluster is at best about 15 degrees above the southern horizon. From my home in Northumberland I'm always viewing this part of the sky through severe light pollution created by Newcastle, Cramlington, Blyth, Ashington and nearby village lights.
The pictures below show what I have to contend with and how I deal with it.
The picture on the left is one of the raw images and it's almost washed out with the pinkish contribution from streetlight pollution. The picture on the left is a "map" of the background created with free software called IRIS. Basically the second picture gets subtracted from the first to leave something looking a lot healthier that eventually ends up as the picture at the top of the page. I described the exact process in an earlier article and it's absolutely crucial to obtaining deep sky images from light polluted skies.
I really wanted to wake up at 5am and get a solid 90 minutes of images of Comet Lovejoy. In the event I eventually fell out of bed at 6am and only managed about 22 minutes.
This is how C/2013 R1 Lovejoy looked this morning.
The comet is past perihelion and getting further from the Sun. This morning it was about 79 million miles from the Sun (between the orbits of Venus and Earth) and about 107 million miles away from Earth.
Comet Lovejoy is becoming harder to observe with every passing morning. The orbit is taking the comet further to the south in the sky which means it is heading towards my southeast horizon. Lovejoy is also fading as it heads away from the Sun. There can't be many more chances to get images like this. The forecast for tomorrow is good so I'll have another attempt at getting 90 minutes of pictures - perhaps enough to get a bit more of the comet's tail.
I've been taking astronomy images with a DSLR and various telescopes for about 2 years. The slideshow below are what I hold to be my best pictures of the year.
Caught this strange object on one of my pictures of NGC 663 in Cassiopeia taken on Christmas Eve.
Not sure what to make of it. Luckily it only ruined one frame out of about 30.
Dr Adrian Jannetta
Guitar strummin' explorer of the universe. Mild mannered maths teacher by day and astronomer by night.