WADHURST ASTRONOMICAL SOCIETY

JUNE NEWSLETTER 2007

INDEX: MEETINGS, OTHER NEWS, CONTACTS

MEETINGS

PROPOSED VISIT TO BELMONT HOUSE

At the Society's May meeting Phil Berry announced that the visit to see the largest private collection of clocks is to take place on Saturday 22 September 2007.

We would meet at Belmont House at 1030 for coffee and biscuits and then be shown round the clock collection beginning at 1100.  The tour will last about two hours but we would need to find our own way there.  Members may wish to arrange to travel together where possible.

Belmont House is about 4 miles south, southeast of the town of Faversham, on Throwley Road.  More details of the location will follow later.

Originally, we had thought we would visit Greenwich Observatory later the same day, but it is felt that this would be too much for a Saturday, so we are hoping to arrange a separate visit to Greenwich later when we may be able to visit the newly opened planetarium as well.

A total of 17 members have so far said that they would wish to come to Belmont House and have ticked their name on the list made available at the meetings. The members listed in alphabetical order as attending on Saturday 22 September are as follows:

If you were absent or unaware of the list and your name does not appear but wish to attend or are now no longer able to attend please let Phil know by the July meeting at the latest, or by email before, as final numbers are required.

MAY MEETING

Pixel Magic

Talk given by Nik Szymanek at the Society's May meeting

Most members know and admire the astro-pictures of Nik Szymanek and at the Society's May meeting he explained some of the ways in which he achieves those remarkable results with the aid of modern computer software.

During his talk Nik displayed the output from his laptop on a digital projector enabling us to watch as he manipulated images with various programmes into images that revealed details that weren't apparent to begin with.

He mainly uses two software programmes, Adobe Photoshop CS and Maxlm DL's DDP (Digital Development process).

As an introduction to what can be done, we were shown a scanned film image of the comet Hale-Bopp taken during its close pass in 1997.  The film image suffered from a lot of low-pressure sodium light pollution as a very obvious greenish background resulting in an image one would have happily discarded.

First, using Photoshop, Nik demonstrated the programmes ability to correct for the light pollution in the dark part of the background sky by separating the image into its three channels, red, green and blue, then correcting the background sky on each to black.

Then he used gamma control to stretch the darker parts of the image, where much of the interesting detail lies but without compressing the brighter parts too much.  The results enabled us to see more detail in the darker parts of the tail without losing too much in the head of the comet.  By further enhancing the image in the three separate colour channels and working particularly on the blue channel it was possible to resolve the comet's separate blue ion tail.

Finally the image was sharpened up using the Photoshop "unsharp" tool.  By comparing this image with the original was very impressive.  A useful advantage is that the unsharp tool can be masked to only operate on certain selected areas of the image.

Using the History List it is possible to go back through performed adjustments to an earlier point, allowing further corrections to be made.

In another example, the star cluster M92 in the Hercules constellation is very contrasty and in preserving the fainter stars there is the danger of losing detail in the brighter central cluster.  Here, we saw how different transfer curves can keep the bright areas from crushing whilst enhancing only the darker areas.  There are three basic curves; linear, gamma and logarithmic, all with their special advantages.

One particular transfer curve that Nik uses is part of the Maxlm D4 software programme.  In this programme there is a facility called "Screen Stretch" where another curve lies somewhere between the gamma and logarithmic curves and is called the Digital Development Process curve.  This was created by an amateur astronomer in Japan.

Using DDP on the Black Eye galaxy, M64, Nik showed how it was possible to really bring out the fainter stars whilst preserving great detail in the heart of the galaxy by carefully using the Screen stretch.

Nik went on to say that in most of his work, he uses many short exposures that can be combined to make one long exposure.  One single long exposure can result in it being ruined, for example by a passing aircraft.  Noise is also added during an exposure at the square root of the whole image.

An original image of M87 in Virgo showed a diffused area, which by using Screen Stretch revealed a jet that is said to be travelling away from the galaxy at the speed of light.  This is normally not seen due to over exposure.

When imaging the Moon, Screen Stretch can also be used to increase the contrast, producing the effect of apparently sharpening the craters.

Nik tells of when professional astronomers on La Palma were given a new imaging camera to assess, were only permitted to use the telescope for ten minutes.  During this time they tried to image M51, the Whirlpool galaxy, but managed 5-minute exposures only in red and green.  Some time later, the King of Spain was being shown around the observatory and was asked if there was anything he might like to see.  It was suggested that he looked at M51 giving the astronomers a chance to finally get their remaining 5-minute blue exposure.

The Whirlpool galaxy has an arm stretching out on one side with a diffused blob at the end of it.  By astute use of DDP it was possible to show the detail of the blob and it could now be clearly seen as a separate galaxy that is believed to have passed close by M51 and had drawn out some of the material in the arm.

Using Photoshop we were shown another trick, this time using layers.  For this example two identical images of NGC 2903, a spiral galaxy in the constellation of Leo, were placed one over the other so that only the top layer was visible.  This image was then enhanced to bring out the detail of the fainter stars but inevitably crushing out detail in the central core at the same time.  Then by using the erasing tool with a feathered edge the centre was gently erased, revealing the layer underneath with all the original detail of the core.  The combined image showed details that could not be appreciated in the original image.

Another example of the use of Photoshop was shown using an image of M82, a starburst galaxy.  One of the images was in Hydrogen Alpha light, producing a red image.  This was enhanced and placed on the clipboard whilst the remaining two channels were adjusted for optimum background black sky and now showing detail in the dark lanes of the galaxy.  The red image was pasted back from the clipboard, resulting was a very much clearer image of M82. 

We were also shown how noise can be reduced by using the De-speckle tool on each of the colour channels before recombining them.

JUNE MEETING

Wednesday 20th June 2007   This will be an open and informal evening when we have the opportunity to talk to other members.

A number of telescopes will be at the meeting for discussion and demonstration of how they get used.

Any member able to give a short talk will be very welcome and should contact Phil Berry who would be delighted to hear from them.

FUTURE MEETINGS

Wednesday 18th July 2007   George Satterthwaite will be giving a talk about "George Airy and His Contribution to Positional Astronomy".

August

There is no meeting of the Society in August, but once again, we have been kindly invited to an Astro Barbecue hosted by Michael Harte and his wife at Greenman Farm on Saturday 25th August 2007.

Greenman Farm, Wadhurst is on the south side of the B2099 immediately to the west of the railway over-bridge.  All Society members are invited and Michael suggests that members aim to arrive at about 7.00 pm.

You will only need to bring your own food and drink, as everything else will be provided.

In previous years this has been a very enjoyable event and gives members a chance to meet others in a relaxed and pleasant atmosphere.

Members are invited to bring telescopes, binoculars and anything else of interest, but mainly themselves.

Wednesday 19th September 2007   George Sallitt will be giving a talk about "Webcams", a subject that will interest a number of members keen to get involved with this cheaper but satisfying method of imaging.

Wednesday 19th September 2007   George Sallitt will be giving a talk about "Webcams", a subject that will interest a number of members keen to get involved with this cheaper but still satisfying method of imaging.

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OTHER NEWS

TELESCOPE FOR SALE

Bob Seaney has an eight-inch LX 10 reflecting telescope for sale.

This is an ideal telescope for the more serious amateur astronomer and would provide the opportunity to get involved in more serious observing.

The telescope is in excellent condition and has its own travelling box.  It has an equatorial battery driven mount with hand controls.  The instrument takes standard one-and-a-quarter-inch eyepieces and comes with a 40 mm eyepiece.

The telescope comes with a heavy metal tripod for good stability.

Bob is asking £450, which is very reasonable.

JUNE NIGHT SKY

Planets

Mercury should be visible at magnitude 0.5 in the north-west at the very beginning of the month. Always wait until the Sun has set before sweeping for it with optical aid.

Venus reaches greatest eastern elongation on June 9th when its magnitude will be -4.3. It is unmistakable in the twilight sky setting some three hours after the Sun.

Mars is still a morning object, rising around 02.00 BST, in the constellation of Pisces (the fishes) but moves into Aries (the ram) later in the month. Observations are hampered by the planet lying relatively low in the sky.

Jupiter is an evening object at magnitude -2.6 in the constellation of Ophiuchus (the serpent bearer). By the middle of the month it rises well before the Sun has set, although it is never more than 17º above the horizon. I observed it at 22.45 BST in the middle of May and was able to see the four largest moons and some surface markings, although the unsteadiness of the atmosphere at that elevation makes very detailed observations difficult. Despite this it is still worth following the progress of the moons from night to night.

Saturn is still an evening object at magnitude 0.6 in Leo (the lion). On June 30th Saturn and Venus pass close to each other (within about one degree), which could present an opportunity for astro-imagers.

Lunar Occultations

For this months occultations I've included five events for stars (two of them double) down to about mag 7 that occur before midnight.  DD indicates that the star disappears at the dark limb of the moon. All times are in BST.

Lunar Occultation of Venus

There is also a daylight occultation of Venus by the crescent Moon, which should be an easy event even in binoculars. Be careful not to sweep around the sky and inadvertently look at the Sun! Times are in BST.  RB indicates a re-appearance on the bright limb.

ISS

Brian Mills

NASA SPACE PLACE

The Ions of Dawn

by Patrick L. Barry

This summer, NASA will launch a probe bound for two unexplored worlds in our solar system's asteroid belt-giant asteroids Ceres and Vesta. The probe, called Dawn, will orbit first one body and then the other in a never-before-attempted manoeuvre.

It has never been attempted, in part, because this mission would be virtually impossible with conventional propulsion. "Even if we were just going to go to Vesta, we would need one of the largest rockets that the U.S. has to carry all that propellant," says Marc Rayman, Project System Engineer for Dawn at JPL. Travelling to both worlds in one mission would require an even bigger rocket.

This is a trip that calls for the unconventional. "We're using ion propulsion," says Rayman.

The ion engines for the Dawn spacecraft proved themselves aboard an earlier, experimental mission known as Deep Space 1 (DS1). Because ion propulsion is a relatively new technology that's very different from conventional rockets, it was a perfect candidate for DS1, a part of NASA's New Millennium Program, which flight-tests new technologies so that missions such as Dawn can use those technologies reliably.

"The fact that those same engines are now making the Dawn mission possible shows that New Millennium accomplished what it set out to," Rayman says.

Ion engines work on a principle different from conventional rockets. A normal rocket engine burns a chemical fuel to produce thrust. An ion engine doesn't burn anything; a strong electric field in the engine propels charged atoms such as xenon to very high speed. The thrust produced is tiny-roughly equivalent to the weight of a piece of paper-but over time, it can generate as much speed as a conventional rocket while using only about 1/10 as much propellant.

And Dawn will need lots of propulsion. It must first climb into Vesta's orbit, which is tilted about 7 degrees from the plane of the solar system. After studying Vesta, it will have to escape its gravity and manoeuvre to insert itself in an orbit around Ceres-the first spacecraft to orbit two distant bodies. Dawn's up-close views of these worlds will help scientists understand the early solar system.

"They're remnants from the time the planets were being formed," Rayman says. "They have preserved a record of the conditions at the dawn of the solar system."

Find out about other New Millennium Program validated technologies and how they are being used in science missions at:

http://nmp/TECHNOLOGY/infusion.html

(At the time of writing the Newsletter, I could not make this site work.  Editor)

While you're there, you can also download "Professor Starr's Dream Trip," a storybook for grown-ups about how ion propulsion enabled a scientist's dream of visiting the asteroids come true.  A simpler children's version is available at: http://spaceplace.nasa.gov/en/kids/nmp/starr.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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CONTACTS

Chairman   John Vale-Taylor  pjvalet@tiscali.co.uk

Phil Berry  01892 783544 phil.berry@tiscali.co.uk

Treasurer  Mike Wyles  01892 542863 mikewyles@globalnet.co.uk

Publicity & Website  Michael Harte  01892 783292 michael@greenman.demon.co.uk

Newsletter Editor  Geoff Rathbone  01959 524727 Geoff@rathbone007.fsnet.co.uk

Any material for inclusion in the July Newsletter should be with the Editor by June 28th  2007

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