Astronomy Diary

The Sky at Night - July 2008

2008-07-07T12:31:00.000-07:00

This month's programme was hosted by Chris Lintott from the Mars Phoenix mission control headed by Professor Peter Smith.

The Phoenix lander was sent to the northern polar region of Mars and landed in Green Valley of Vastitas Borealis on May 25th. The main mission was to find water ice beneath the Martian soil. On landing, the retrorockets of the lander displaced the top soil to reveal ice beneath.

The landing site is similar to the areas of permafrost at Earth's northern latitudes as the land looks like a patchwork of thermally contracted polygons. After initial tests, the soil was found to be slightly alkaline and much like Earth's soil. In fact, Mars could support Earth vegetation.

The main tool on Phoenix is a digging tool for taking soil samples. These samples can then be viewed through an on-board microscope. There is also an oven for baking samples and boiling off gases and water vapour. After some teething problems the oven is now working.

There is also a camera with mono and stereo full-colour imaging. In addition there is a simple device for measuring Martian winds. The Martian atmosphere is only 1% of Earth's atmospheric pressure so a very sensitive pendulum was installed in place of an electronic anemometer. By photographing the movement of the pendulum, scientists can determine wind direction and relative strength.

The Sky at Night - June 2008

2008-06-07T05:50:00.000-07:00

This month's programme had a brief update on the Mars Phoenix landing. The programme then went on to discuss returns to Saturn and Jupiter to look for signs of life amongst their satellites. Professor John Zarnecki of The Open University championed a return to Titan to follow up the findings of Huygens probe and look for the building blocks of life.

Professor Michele Dougherty of Imperial College argued a return to Jupiter to look for life on the Galilean satellites. In particular, a visit to Europa that is believe to have liquid oceans under its ice surface.

The Sky at Night - The Battle of the Giants

The Sky at Night - May 2008

2008-05-05T02:13:00.000-07:00

The May edition of The Sky at Night was titled "You Just Don't Know" and was a round table discussion about the limits of human knowledge. Around the table sat Sir Patrick Moore as "Devil's Advocate" due to it being the 666th edition of the programme, Dr Chris Lintott, Dr Kate Land, and Professor Gerry Gilmore.

The assembled brain's trust of astronomers discussed the known universe and attempted to guess what was left to be understood. The viewer was reminded of the current theory of the Big Bang Model for the universe. Dark matter and dark energy were postulated as fitting current known models for the expansion of the universe.

It was said that the visible universe accounted for but a fraction of the mass of the universe and that exotic materials probably accounted for the rest. The guests then talked about how privileged astronomers were to view the universe at this time, as the past and future will not be conducive of observations.

In conclusion the guests said that the expansion of the universe was accelerating and the future will be a dark and lonely place as space, time and matter expand beyond the capabilities of visible observation.

The Sky at Night - We Just Don't Know

Choosing a telescope or binoculars

2008-04-29T02:11:00.000-07:00

Amateur astronomy has made great technological advances in the last few years that amateur astronomy can claim to be the only science that can assist the professionals. Just try getting a synchrotron into your bedroom for some particle physics experiments!

Don't go rushing out to buy a telescope, especially not those little plastic 2-inch refractors and 4-inch reflectors promising you 500X magnification. They are usually of very poor build quality and though cheap will disappoint you and turn you off astronomy for life.

Better still, buy yourself a good pair of binoculars. I recommend a pair of 10X50. The 10 refers to the magnification and the 50 to the diameter of the object lens in millimetres. And, if you decide that you don't like astronomy you can use them to keep your eye on the neighbours!

If you do want to buy a telescope then take a look at the scopes from companies such as Meade, Orion or Celestron. They are well-made and will give a lifetime of enjoyment. There is a thriving second-hand market on eBay if cost is at a premium and you don't mind not having the latest of everything, unlike me.

Read these articles on choosing a telescope:

BBC - Patrick Moore's Guide to Buying a Telescope

Astronomy Magazine - Buying a telescope

Messenger from Mercury

2008-01-16T09:43:00.000-08:00

NASA's MESSENGER probe has sent back its first image of Mercury. It shows a planet pocked with craters, much like the Moon.

Another similarity with the Moon is the lack of atmosphere. There is a tenuous atmosphere replenished from places like the solar wind but nothing like Venus, the next planet closest to the Sun after Mercury.

The planet gives us a foretaste as to the fate of the Earth when the Sun swells to become a red giant. Mercury's surface temperature ranges between 90 and 700K.

The MESSENGER probe will settle into an orbit around Mercury by 2011, after two more fly-bys. The probe will then examine the chemical composition of the planet and its magnetosphere.

Mars rovers still working

2008-01-03T05:34:00.001-08:00

Four years after starting their 90 day missions on Mars, rovers Spirit and Opportunity are still going strong. Together they have ranged over 10 miles and have taken over 200,000 images of the Martian surface.

They have done a lot of good science, including supporting theories about water having once been on the surface Mars. With the onset of the Martian winter the rovers are now parked and awaiting spring before continuing their record breaking activities. Let's wish them a long life so they may welcome ESA's ExoMars rover in 2014.

Cassiopeia, C14 and Perseus

2008-01-02T08:25:00.001-08:00

[click to enlarge]
20:24:10 UTC 1st December 2004
Canon EOS 300D with 18mm lens at F3.5
120 sec exposure at ISO 1600

It is very enjoyable taking wide-field images of whole constellations. This image is of two constellations, Cassiopeia and Perseus. It is not hard to take this kind of image and doesn't require much equipment. A Canon EOS 300D SLR camera with the supplied 18-55mm zoom lens was used.

The camera had the benefit of sitting on a motorized equatorial mount, which allowed the camera to follow the stars as the Earth rotated on its axis. This permitted a longer exposure to bring out more of the Milky Way that runs through these constellations.

A good image can still be taken without a motorized mount but shorter exposures are needed so that stars don't trail. The image will have fewer stars on it but it will still be possible to make out all the main stars in any particular constellation.

Between the two constellations is the double cluster C14, which is part of Patrick Moore's Caldwell Catalogue.

Not much processing is needed with wide-field images like this. All that was done to this image was the adding of lines to connect up the stars in each constellation.

Paint Shop Pro

2007-12-29T02:04:00.000-08:00

For processing images Paint Shop Pro graphics editing software is used. It is a much cheaper alternative to Photoshop and for astrophotography it does everything you need of it.

There are many useful functions in Paint Shop Pro. One such function is "image arithmetic" whereby one image can be subtracted from another. This is particularly useful when cleaning up an original image by removing the errors in a dark image from the original.

Other useful functions in Paint Shop Pro are the cropping, resizing, sharpness, brightness and colour balance functions. The colour balance function is useful for altering the red, green, blue (RGB) balance in a photograph so as to accentuate a particular colour.

The matt function is very useful for layering photographs on top of each other. For example, you might take various exposures of different time length of the Orion nebula (M42) so as to bring out different features in each photograph. Matts can then be created to only allow that part of an image that is correctly exposed. Finally, all the images are merged to create a single image whereby all elements are correctly exposed.

In the case of M42 the central star cluster in the dust cloud needs a shorter exposure than the surrounding dust cloud. Two separate images with the correct exposure times can then be merged using matts to create a composite image.

SLR imaging camera

2007-12-27T07:44:00.001-08:00

Many of the images on this website were taken with a Canon EOS 300D. As is usual for an early adopter a lot more was paid for the camera than it can be had for now.

The camera comes with a Canon EF 18-55mm zoom lens, which is good for wide angle shots of star fields, constellations and comets. In addition a Canon EF 200mm f/2.8L II USM lens was purchased as an intermediate between the zoom lens and imaging through the telescope.

The camera is used for imaging in two ways. For wide field imaging the camera piggy-backs on the telescope (to make use of the motor driven mount) and uses the camera's own EF lenses. For imaging the sun, moon, planets, star clusters and galaxies the camera is connected without a lens directly to the eye piece tube of the telescope by way of a T ring. In this way the telescope becomes the lens for the camera.

To take photos there is a shutter release cable to keep the camera shutter open for as many minutes as required for long exposures. The cable has the added advantage of negating the need for the user to touch the camera and shake it whilst images are being taken.

Images are stored as raw bit maps on compact flash cards, which are then loaded into the computer for post processing.

Some users have modified their cameras. A major modification is the removal of an infra red (IR) filter from the camera so that it is more sensitive to objects radiating in the IR part of the spectrum.

Another modification is the addition of a peltier cooling device to the camera body. The cooler the camera the less effect heat will have an effect on image quality. Often an image will have red, green or blue dots on it due to anomalies from the image taking process. A similar effect to cooling can be had by taking dark images (images taken with the lens cap on) and subtracting these "darks" from pre-processed images.

Comet Machholz - C/2004 Q2

2007-12-26T10:11:00.000-08:00

[Click to enlarge]
18:51:04 UTC 12th January 2005
Canon EOS 300D with 200mm lens at F2.8
60 sec exposure at ISO 1600

Comet Machholz was discovered by Donald Machholz on August 27, 2004. It has an orbital period of 113,465 years, which is why it was only recently discovered.

This comet was my first attempt at performing observations. The first comet I saw was Comet Halley in 1986 through a cheap pair of binoculars. I then photographed Hale-Bopp in 1997 with a film SLR camera on a fixed tripod.

The image is over-exposed as can be seen with the white-out visible where the nucleus of the comet is to be expected. You can all see some egging of the stars where they have drifted in the image. The photo was taken with a Canon EOS 300D digital camera riding on top of my telescope so that the motor drive could counteract the rotation of the earth. Obviously the scope was not aligned correctly hence the egging of the stars.

The photograph was annotated, showing the direction of the north celestial pole, the coordinates of the comet as determined with a star map and the time the image was taken. You can just make out the galaxy NGC 1333.

Accelerating expansion of the universe an illusion

2007-12-26T03:59:00.000-08:00

Due to my incomplete grasp of mathematics I dropped out of my astrophysics degree in favour of artificial intelligence. However, I still like to keep abreast of the latest in cosmology.

I have always had a problem with some aspects of the expansion of the universe. I don't deny the Big Bang theory. It's just that I like things to be simple. The further objects are away the faster they appear to be travelling. To account for this a glue called dark energy was theorised into existence.

It all seems so messy, as glue usually is. An anti-gravitational force that allows things to travel faster than they should. It sounds like something out of Star Trek.

Cosmologists in Spain have put forward a far better theory. One that postulates that time slows down and creates the illusion of acceleration. Objects at the far reaches of the universe have existed the longest and time has slowed down the most for them.

Imagine myself running against the world's best sprinters. They can run 100 meters in less than 9.9 seconds. I would be lucky to do it in under 12 seconds. However, if I were to run 100 metres with a clock that ran slower than normal then when I finished the race it might read 9.7 seconds. Therefore I had accelerated up to a speed that was apparently faster than the sprint champions who used a "normal" clock.

It is the possibility of clocks running at different speeds that gives rise to this new theory. We already accept clocks running at different speeds when discussing relativity and black holes. There is no problem with time slowing down.

I don't believe that time is constant and that I have been on this planet for 41 years. An off-earth viewer, far away with a faster running clock, might see me living a lot longer than I have. It's just that on this planet tick follows tock at a certain rate and we imagine it do so everywhere in the universe.

Telegraph - Time is running out - literally, says scientist

M45 - The Pleiades

2007-12-25T01:43:00.000-08:00

[click to enlarge]
The Pleiades cluster is the easiest to spot in the sky. It is an open cluster 440 light years away in the constellation Taurus. The stars in the cluster are very young compared to our Sun, aged at only 100 million years. They are very hot as evidenced by their blue colour. The nebulosity around the stars consists of a dust cloud, unconnected to the stars but which they are passing through, reflecting the blue light from the stars.

This image is a mosaic in that it is formed from separate images. Two images were taken as the cluster size was greater than the field of view of the telescope. The images were cleaned of digital anomalies produced by the camera, stitched together using Paint Shop Pro and the blue component slightly emphasized.

My equipment

2007-12-25T01:35:00.000-08:00

For many years I used only a pair of binoculars. They are more than adequate for beginners. Some comet hunters use nothing but binoculars. Today I have a computer controlled Meade Schmidt Newtonian reflector with a 10-inch main mirror. I either observe or image through the eyepiece or piggy-back my digital camera to the main body of the telescope.

My laptop computer has star maps. I can click on any object on the map an the telescope will slew to the object in the sky. Images can be taken with my camera and processed using stacking software and Paint Shop Pro for final processing. I also have software for controlling my camera and a webcam imager.

I will write individual articles on each piece of equipment.

Contacting me

2007-12-24T10:46:00.000-08:00

I would very much like to receive e-mail from fellow astronomers.

Please leave a comment at the end of this post with your e-mail address on it. Comments are moderated so I will delete the comment and e-mail you back.

Thank you.

Introduction

2007-12-24T05:30:00.000-08:00

I am an amateur astronomer and have been so since I was a small child watching the Apollo moon landings. Whenever I could sneak downstairs at 1:30am on a Monday morning, I watched Patrick Moore's The Sky at Night television programme on the BBC. Thankfully the BBC now repeats the programme at more reasonable hours as this old man is rarely able to stay awake beyond midnight.

It was always an ambition to study astronomy at university. However, the realities of modern professional astronomy, and the complex mathematics, led me to feel the subject was not for me. I decided to move into artificial intelligence and the easier finite mathematics courses. It was a good decision as my love for astronomy was unharmed and I continue to enjoy the science as an amateur.

Astronomy is one of the few sciences where amateurs can still perform useful science. With professional astronomers concentrating on big projects there is plenty of scope for the amateur to gain recognition. Be it discovering asteroids, comets or novae, observing meteor showers and the sun optically or with radio, there is much for the amateur to do.

The technology available to amateur astronomers is better than what was available to professionals a decade ago. Imaging has never been easier. Computer controlled telescopes are the norm.

I hope you enjoy this diary of my observations, tips, tricks and comments on astronomy news.