40 Years of CCD Imaging

The charge-coupled device or CCD was invented 40 years ago and is now commonly used in a wide range of cameras including those used by astronomers to produce the most stunning deep-sky images.

The first devices were designed as computer memories but this application never really took off, mainly due to their susceptibility to cosmic rays. However, their potential as imaging devices was realised at an early stage and developed rapidly.

Early devices had a few pixels in linear arrays and were used in scanning applications. For example, earth-observation satellites used the motion of the satellite to scan linear arrays along the ground to create a very long and narrow two-dimensional image.

Early devices were not suitable for astronomy but a two-dimensional RCA chip with 320 x 512 pixels was cooled by liquid nitrogen and used on the 1-metre telescope at Kitt Peak in 1979. Initially their high cost and complexity confined CCDs to professional observatories but nowadays amateur astronomers are routinely using them to produce images that professionals struggled to do less than twenty years ago.

Today we have two-dimensional detector arrays with millions of pixels. As far as I'm aware the largest device was produced in 2006 and measures 10cm by 10cm and has 111 million pixels. It was developed for the US Naval Observatory for the accurate measurement of star positions.

CMOS sensors are replacing CCDs in many applications where cost is important but the CCD continues to dominate in areas where high quality is required.

My personal experience of CCDs was in designing electronics for some of the earliest ones we used at  the Royal Greenwich Observatory and their use on the Isaac Newton Group of Telescopes. Lee's experience of using the CCD cameras available to amateurs is much more extensive so between us we should be able to give you any advice you might need if you want to get started in astro-imaging or to improve your technique.

Astronomy for Absolute Beginners

Jeffrey will be giving his popular one-day introduction to astronomy on Saturday 26th September. Full details are on our web site or you can call us on 01954 211288 to book. If you are new to astronomy and want a gentle overview that will give you a good base to build on then this will be an enjoyable day well spent.

Cosmos and Culture - by Jeffrey Barham

Jeffrey visited the Science Museum and enjoyed its latest exhibition so much that he suggetsed I bring it to your attention. Here is his report:

" The Science Museum in London is currently holding an exhibition about the effect that astronomy has had on civilisation. Many of the exhibits are things that we've all read about, but rarely get a chance to see.

Telescopes from the past 400 years are there - a copy of Galileo's, Newton's tiny reflector, Herschel's instruments with which he discovered Uranus and James Naysmith's revolutionary 20" reflector, designed so the eyepiece was in a fixed position. There's also a mirror from Herschel's 40-foot telescope (and one of his polishing machines) and a 3-ton mirror from Lord Rosse's Leviathan of Parsonstown.

All sorts of astronomical instruments are on display as well as influential books by Ptolemy, Kepler, Copernicus and Galileo.

There are touch screens all round the exhibits to give valuable information about what you can see. This is a truly worthwhile addition to a day out in London - and of course it's free. The exhibition is open until the end of 2010. "

Meade's Latest Telescope - the ETX-LS

Meade revolutionised the amateur astronomy market when it introduced the first ETX over a decade ago. Compact and affordable with excellent optics the ETX 90 made astronomy much more accessible and sold in enormous numbers.

Computer control was added later and the larger 125mm and 105mm versions were added to the range. After a short setup procedure the user was now able to select any object from a datbase of thousands which the ETX would find and then track. Although Meade led the way, other manufacturers quickly followed and computerised 'GOTO' telescopes are quite common. Some ranges are only available with computer control.

But Meade have now taken the concept a stage further and have automated the setup procedure so all the user has to do is place the telescope on its tripod in the open and switch it on.

They've incorporated this technology into the ETX-LS which is now available in quantity in the UK. We received our first batch last week and they sold out immediately. More are due soon and the ETX-LS looks set to dominate this year's observing season.

The ETX-LS also incorporates Meade's Advanced Coma-Free optics, an improvement on the basic Schmidt-Cassegrain optics that have become so popular. The six-inch aperture is a new design for Meade and provides excellent images.

Our display model is in Leeds this weekend where Lee is showing it at the British Astronomical Association meeting but it will be back in the showroom on Monday if you would like to see it. Find it here on our web site.

New Bird-watching Telescope from Celestron

You may have seen adverts appearing in bird-watching magazines for the new Regal F-ED field scopes from Celestron. I tried the 80mm version last week and was very impressed by its performance with the supplied eyepiece.

However, an interesting feature is that it uses a standard 1.25-inch eyepiece fitting, making it possible to use a wide range of astronomical eyepieces. I tried it with several high-quality eyepieces, including a 13mm Ethos which gave a stunningly wide field of view.

Chris Garvey pointed out that this allowed astronomical eyepiece filters to be used as well, the most useful being a polariser which will reduce reflections from water and glass. We tried this on a window on a nearby unit and it proved very effective. Chris has tried it on a lake where it made a remarkable difference, taking glare away from swimming birds and even allowing their legs to be seen beneath the surface.

Stocks have not yet arrived in the UK but are due soon. Interest is already building and we expect this to be a very popular telescope. You can find it here on our web site.

Astronomy Picture of the Day

The recent night launch of Space Shuttle Discovery on August 28th featured as the Astronomy Picture of the Day (APOD) on September 3rd. If you're not familiar with APOD you might like to look at the archive on this web site.

If you like the pictures, you can instal software that will download the APOD and display it as your desktop background each day. This gives you a varied and stimulating backdrop that is not only attractive but can be thought-provoking. Details and the download can be found here.

Superior Swft Boxes

I love the sound of swifts over the house on summer evenings and like to watch their crescent-shaped wings as they display their flying prowess. So a recent enquiry from a customer who was looking for a CD of swift calls prompted me to do a little research.

I located the CD and some interesting facts about swifts. I knew they travelled thousands of miles on their annual migration but didn't realise that swifts nesting in Britain will sometimes travel to France or even Spain in search of food for their young if it's in short supply here. Apparently, they can be gone for two or three days while the young are left to fend for themselves.

Coincidentally, our suppliers have changed the design of their swift box to make it more user friendly. It now has a sloping front so the birds can approach it from below then drop away when leaving the nest. Swifts are superbly adapted for flight but have very short legs and are out of their element on the ground. They have difficulty launching them selves from a level surface.

Anyway, I plan to put up a swift box ready for next year and hope to attract them. I don't know if I'll go as far as playing them the swift call CD; I'll keep that as a fallback option if they don't use the box next year. You can see the new box here.

International Space Station

The Space Station will make visible evening passes over Green Witch beginning on September 8th so I hope to see the Shuttle Discovery flying alongside it after separating prior to its return to Earth on September 10th. Visit www.heavens-above.com for predictions for your location.

And finally...

Australian astronomers have completed a study to find the best site for an observatory in Antarctica and have selected Ridge A, about 150 km from Dome A, the highest point on the continent.

They estimate that images taken from the site can be three times sharper than the best from existing ground-based observatories. The main problem is the average winter temperature which is around minus 70 Celcius. But they shouldn't have any trouble keeping the beer cool.

Clear Skies and Best Wishes

Neil

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