April Fools' Star Party

Don't forget we will be holding a star party on April 1st at the Green Witch showroom. It starts at 9 pm and will be a good opportunity to take a close look at Saturn while it is still in a good position. Next year the rings will be closing up and the view will not be so good again for several years.

Cassini takes a Shower

The beautiful images of Saturn that Cassini sent back as it approached the planet are some of the most stunning pictures from space. But Cassini continues its 4-year mission to the ringed planet and recently has been taking a closer look at the moon Enceladus and its geysers. On March 18th at a speed of around 32,000 kph it passed within 50 km of the surface in an attempt to fly through a geyser to collect and analyse the vapour plume coming from cracks near the moon's south pole.

A software glitch stopped one of the on-board instruments from collecting samples during closest approach but it did work before and after approach. Very detailed images of the source of the plumes were obtained and these are being compared with images of the north pole which are quite different. A similar fly-by is planned for October.

Data from these approaches will enable scientists to determine the composition of the plume and compare it with the halo of particles that surrounds Enceladus. This in turn will help explain the origin of the plumes and whether icy particles from them are feeding and helping to maintain Saturn's E-ring.

International Space Centre at Harwell - a step in the right direction?

When reading about Cassini it is easy to forget the contribution that Britain made to the mission. In fact, it's easy to forget we have a thriving space programme; regular readers will know this is something I feel quite strongly about, but perhaps things are about to change.

The government has announced that an international space centre will be created on the Harwell site in south Oxfordshire. Harwell was famous as the Atomic Energy Research Establishment, home of the UK's civil nuclear research programme. I started my career in Hanger 9 at Harwell as a Student Engineer and saw the tail end of its nuclear research programme. Since then it has changed its role completely and is a Science and Innovation Campus with over 250 start-up companies on site.

Next door is the Rutherford-Appleton Laboratory, the largest establishment of the Science and Technology Facilities Council (STFC). Its main role is to support research into high-energy physics but it also makes vital contributions to space and astronomy.

An international space centre alongside the Rutherford-Appleton Laboratory will produce one of the largest high-tech campuses in Europe. It will draw in resources that are currently deployed elsewhere which will not suit everyone but hopefully it will give our space programme the public profile it needs.

The proposal is part of the UK's Space Strategy published by the British National Space Centre (BNSC), a partnership of government departments that coordinates the UK space programme. Many commentators have pointed out the irony of publishing an ambitious space strategy at a time when  funding shortfalls are threatening so much of the current astronomy programme.

There is a long way to go to raise the profile of the UK space programme but having a recognised and well-publicised centre at Harwell could be a step in the rght direction.

Advice on the Green Witch Web Site

If you haven't visited our new web site you won't have seen the product reviews and other advice we've added recently. There are articles on zoom eyepieces, Hyperstar, the Revelation Eyepiece Kit and several others. Ralph is testing out a wide range of binoculars with a view to publishing a recommended list to help simplify the bewildering range of choice. Please let us know if there is anything else you would like to see added.

Easter Closing

As in previous years we will be closed from Good Friday to Easter Monday inclusive. We open again on Tuesday March 25th.

Easter is very early this year which has prompted the usual calls for its date to be fixed. The rules for calculating the date of Easter are based on natural phenomena, that is, the spring equinox and the phase of the Moon. My personal opinion is that it would be a shame to lose this reminder that our lives are affected by the Moon as well as the Sun, even if street lights and living away from the coast make it seem irrelevant in the modern world.

March Sale

Our March Sale is underway and there are plenty of bargains. There is a list of many of them on the web site. Just click on the red banner for details

Saturday Morning at Green Witch

We have always encouraged customers ot call in for a chat or to seek advice. If we're not too busy then we're happy to supply tea or coffee and if we are busy we don't mind if you make your own. For several months we've had a regular small group meeting on Saturday mornings to discuss their latest observations and images. Why not join them if you'd like to share your problems and experiences?

Looking South at 10 pm (from Cambridge, England)

Leo is the constellation that dominates our southern view. His head is on the meridian and his body stretches away to the left. Leo's head is the distinctive 'backwards question mark' or sickle shape with the bright star Regulus at its base. Alongside Regulus we find Saturn, only 3 or 4 degrees away.

Below them and to the left, about 7 degrees from Saturn is the Full Moon so there is no excuse for even a beginner to look in the wrong part of the sky. The presence of the Moon may hide the fainter stars but unless it is hazy or cloudy the brighter stars and the shape of Leo should be easy to identify.

While the Moon is acting as an unmistakable marker check out the position of the pointers in the Plough. Following their line in one direction takes you to the Pole Star but following them in the opposite direction will bring you back to Leo's back. Take note of this for future reference. Even when Leo is below the horizon you will always be able to estimate where he is.

Between Leo and the Plough and just to the left of our meridian lies Leo Minor. This is not a very prominent constellation at the best of times and the Moon will make it difficult to see. But look for it over the coming days as the Moon moves away and Leo Minor inches its way onto our 10 pm meridian.

Below Leo we have more of Hydra, the snake we've been following for a few weeks. Again the Moon will make it hard to identify so look for it when the Moon has moved on.

Of course, the Moon itself should not be ignored, even though many surface feature do not stand out when illuminated directly from above. Other features show up better so look for the bright rays spreading out from major craters. You can imagine this lighter coloured material being thrown out by the impact that created the crater.

The Moon is noticeably much brighter when it is full than in its other phases. This isn't just due to more of its illuminated surface being visible, it's also due to preferential backscattering of light by dust particles on the Moon. When we look at it from approximately the same direction as the Sun each part of the Moon looks much brighter than when we view if from one side. The mechanism is different but it's a bit like looking at an LCD screen from directly in front rather than from one side.

If you want to view the Full Moon through a telescope you will definitely benefit from using a Moon Filter to reduce the glare. These are quite cheap and can be used in conjunction with colour filters to enhance faint features.

And finally...

Many amateurs have taken and published images of Mars, Jupiter and Saturn but few take close-ups of Venus. It is usually regarded as featureless from our perspective and its changing size and phase are its most noticable attributes besides its bright appartions as a morning or evening star.

Now the Venus Express spacecraft has sent back images showing a large storm over the south pole. Perhaps it's time to see just how much detail we can detect from here. If you can't catch it in the morning before it gets too close to the Sun then start preparing now to be ready for its appearance in the Summer and Autumn as an evening star.

Clear Skies and Best Wishes

Neil

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