Stirling Engines

Amongst the working model kits of astrolabes and other instruments we sell, you will find a Stirling Engine. The Stirling engine was invented and patented by the Reverand William Stirling in 1816 and has been used for various niche applications over the years. It has some very useful attributes such as near-silent operation and very high efficiency, but has only found use where its high capital cost hasn't been a problem.

It is likely to gain much wider use in the future as it can be used with low-grade heat sources such as heat recovered from waste, and, it is ideal for small-scale combined heat and power systems, sometimes called micro-CHP. One company at least is planning to introduce a unit to replace a conventional domestic water heater which incorporates a Stirling engine to generate around a kilowatt of electricity. The efficiency of generation is claimed to be around 90% compared with around 40% for a conventional powerstation delivering the same amount of power to your home. The unit will connect to the mains and produce most of your electricity with excess power being fed into the grid and top-ups taken from it as needed.

It remains to be seen if this becomes a viable commercial option but it has the potential to make a big contribution to energy efficiency. In the meantime, why not try one of the Stirling Engine kits. They really do work and can be driven by placing them on top of a cup of hot water. I find putting an ice cube of top of them makes them run even better. You can find the kits at http://www.green-witch.com/acatalog/Working_Model_Kits.html

44th International Astronomical Youth Camp, July 20th to August 9th 2008, Sayda, Germany

I hadn't heard about these until recently but thought I would pass the information on in case it's of interest to you or someone you know. It came via the Federation of Astronomical Societies. The Youth Camps are for 16 to 24 year-olds and include astronomy projects catering for a range of interests. They also include other activities and look like great fun. Full details can be found on the web site at http://www.iayc.org/index.php

Nebula Star Party, Tuesday 4th December 2007

Our next Star Party is tomorrow, December 4th and features Nebulae. At present the weather forecast is favourable so we hope you can make it. It's worthwhile even if the weather isn't suitable for observing as we have a cloudy programme planned as well. Lee will talk about nebulae and we will be showing how to get the best views of them. The showroom is open throughout the day until the end of the party which runs from 7 pm to 9 pm.

Observing Mars

Mars is approaching opposition and is well-placed in the night sky for observing so it will be the object featured at our Star Party on Tuesday 18th December 2007. Ralph will be demonstrating how to take high-resolution images using a webcam. This will include using Registax software to get the best possible image.

Whatever telescope you use to observe Mars it is worth considering an orthoscopic eyepiece. These are generally acknowledged to give the sharpest, clearest images in the centre of the field so are ideal for small objects such as planets. Baader have produced a range of orthoscopics that are very good value and it is worth adding one to your collection for planetary use. They may not be on the web site when you receive this newsletter so please contact Lee for details.

Lunar Exploration

While researching the talk I gave about the Moon at our Star Party on Tuesday 20th November I found a time line for lunar exploration on one of the NASA web sites. You can see it at http://nssdc.gsfc.nasa.gov/planetary/lunar/lunartimeline.html

One of the things that struck me was the way that interest in lunar exploration seemed to die out after the Apollo missions. To recap briefly, the first lunar probe was the Russian Luna 1 which flew by the Moon in 1959. Activity was then fairly intense for the next decade leading up to the first manned landing by Apollo 11 in 1969. This was followed by several missions each year for a while but the last mission for almost 14 years was Luna 24 in 1976 which brought back surface samples.

The next exploration came in 1990 when the Japanese Hiten satellite flew by and launched an orbiter. Interest picked up again slowly but in the last two years has increased considerably as emerging space programmes in India, Europe, China and Japan have joined the occasional US mission.

The 14-year break was understandable after the manned landings as routine missions were going to be something of an anti-climax. But what sparked interest again? It may only be a coincidence but Wallace and Gromit visited the Moon in 'A Grand Day Out' which was released in 1989. It's not on the NASA time-line but it may have started the ball rolling again.

Steve's Pictures

Steve Loughran started astrophotography in January this year (2007) and has worked hard to perfect his technique. He uses a Celestron 8-inch SCT and a piggy-backed William Optics 66mm refractor. He takes images with either telescope, using the other as an autoguider. His results are excellent and we've posted some of them on our web site to give you an idea of what you can achieve if you are prepared to put in the effort. Please take a look at them at http://www.green-witch.com/steveloughrangallery.html
 
Steve's Horsehead Nebula, taken with the 66mm refractor looks similar to the image taken by David Malin at the prime focus of the 3.9m Anglo-Australian Telescope many years ago when he was the acknowledged world-leading astrophotographer. This indicates how much difference CCD cameras make and should be an inspiration to any aspiring astrophotographers.

David Malin's contribution to astrophography was due as much, if not more, to his dark-room technique than to his image-taking. The same is true of using a CCD where image-processing is carried out on the PC rather than in the dark room. If you would like help to get started in astrophotography or to improve your technique then I recommend talking to Steve; he's often in the showroom on a Saturday morning. Alternatively, why not enroll on one of Lee's astrophotography courses and get a leg up the learning curve.

Ralph's Pictures

While Steve specialises in deep-sky targets, Ralph Bell prefers high-resolution imaging of the Moon and planets. If you've been to our showroom you may have seen the large print of the Moon he produced using an Orion Optics 10-inch Newtonian and a web cam. It's a mosaic which we've also placed on our web site so you can take a walk around the Moon's surface. You can find it at http://www.green-witch.com/moonbyralph.html

We've also placed some of Ralph's planet pictures at http://www.green-witch.com/planetsbyralph.html  These give an idea of what can be achieved and Ralph is happy to advise on equipment and technique if you are interested in trying this yourself. We are featuring Mars at our Star Party on Tuesday December 18th . If the weather cooperates then Ralph will be taking and processing images of Mars to demonstrate how it's done.

The Highest Resolution Image Ever Taken

Craig Mackay from the Intitute of Astronomy in Cambridge gave a talk at the Webb Society meeting last Saturday where he described the 'Lucky' technique for deep-space imaging. It is very similar to the technique used by amateurs to image planets with a webcam. A series of frames are taken then the best are registered and added together in the same way that Ralph uses Registax.

The Lucky imager employs a new CCD made by E2V in Chelmsford that has zero readout noise at high speed. Frames are taken at 10 or 100 times per second generating enormous volumes of data which are processed in real time. Early experiments were carried out on the 2.5m Nordic Optical Telescope on La Palma but Craig has since used Lucky in conjunction with a low-order adaptive optics system on the Palomar 200-inch. The result is an image with twice the resolution of the Hubble Space Telescope and is claimed to be the highest-resolution optical image ever taken, anywhere on Earth or in Space.

The technique can be used on larger telescopes but the chances of obtaining sharp individual frames become vanishingly small. Craig's next idea is to combine the input from several sub-apertures onto each of an array of Lucky sensors. Each will see an interference pattern that can be analysed with the closure-phase techniques used routinely in radio astronomy. This will pave the way for high-resolution imaging on current 8 and 10-metre telescopes, as well as future 30 and 40-metre ones.

For more information please see http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site/index.htm

Choosing Binoculars

We recommend trying binoculars before buying to make sure they suit you and your eyes. They need to feel comfortable to hold and you should be able to focus them quickly and easily. That's why we keep a wide selection on display and encourage you to try as many pairs as you want until you find the ones that are best for you. We will advise you on what to look for and we are happy to make recommendations, but the final test is how they look and feel to you.

We know it may not be possible to visit us or to try the binoculars, especially if they are a surprise present. For this reason we will exchange mail-order binoculars that prove not to be suitable provided they are returned in new condition with all packaging intact. The same applies to binoculars bought as presents.

We are all discerning users of binoculars and have our favourites so please call us if you would like a recommendation or to discuss your requirements. There are some excellent binoculars available today and you don't have to buy the most expensive to get the best value.

To read about binoculars and what to look for you may like to visit http://www.green-witch.com/acatalog/Advice_on_Choosing_the_Right_Binoculars_for_You.html

Astronomy Picture of the Day

Did you know you can install a small piece of software that will download the latest Astronomy Picture of the Day from a NASA web site and set it as your PC wallpaper? The software checks for new pictures automatically and updates your wallpaper. Details are at http://nightskylive.net/software/apod/  (We use it and haven't experienced any problems but can't offer a guarantee with this recommendation.)

And finally...

Quite a few of our visitors from further afield make a day of it and visit Cambridge. In the run up to Christmas you might be interested to hear that the new John Lewis is now open, and it's reputed to be one of the biggest in the country. We are not far from the Park and Ride at Madingley Road which is convenient for the town centre, colleges and shops. Why not have a day out in Cambridge and call in to see us?

Clear Skies and Best Wishes

Neil

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