[-] 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 - July 2008 - http://astronomy-diary.blogspot.com/feeds/9061102110343147760/comments/default

[-] 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 - June 2008 - http://astronomy-diary.blogspot.com/feeds/3437921753780361146/comments/default

[-] 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

The Sky at Night - May 2008 - http://astronomy-diary.blogspot.com/feeds/3202802453820269270/comments/default

[-] 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

Choosing a telescope or binoculars - http://astronomy-diary.blogspot.com/feeds/6781285491587515243/comments/default

[-] 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.

Messenger from Mercury - http://astronomy-diary.blogspot.com/feeds/9042022437119095811/comments/default

[-] 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.

Mars rovers still working - http://astronomy-diary.blogspot.com/feeds/5465696374705345855/comments/default

[-] [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.

Cassiopeia, C14 and Perseus - http://astronomy-diary.blogspot.com/feeds/1924455354687868321/comments/default

[-] 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.

Paint Shop Pro - http://astronomy-diary.blogspot.com/feeds/9199998703391132571/comments/default

[-]
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.

SLR imaging camera - http://astronomy-diary.blogspot.com/feeds/4133008083625219117/comments/default

[-] [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.

Comet Machholz - C/2004 Q2 - http://astronomy-diary.blogspot.com/feeds/4139588553887281784/comments/default