The Most Accurate Star Catalogue Ever

Today saw the publication of Hipparcos – The New Reduction of the Raw Data which contains the most accurate star positions ever produced. Hipparcos was an ESA satellite launched in 1989 to measure accurate star positions and hence deduce stellar distances using parallax. The mission nearly ended before measurement began when a booster rocket failed to get it into geostationary orbit. The resulting highly elliptical orbit varied in height between 507 km and 35,888 km considerably complicating both taking the measurements and reducing the data.

Nevertheless, the mission operated successfully with measurements being taken over three and a half years, followed by an extensive data reduction period. One of the data reduction teams was based at the Royal Greenwich Observatory in Cambridge and continued at the Institute of Astronomy when the RGO closed.

Over the last ten years Floor Van Leeuwen, who transferred from the RGO to the university, has continued to work on a systematic error caused by temperature variations when the satellite passed through the Earth's shadow. He has succeeded in identifying and correcting these errors, a mamoth and pains-taking task, to produce the latest catalogue.

Hipparcos data will continue to be the fundamental stepping stone used for distance measurement for many years to come, thanks to Floor and many other dedicated but largely unsung heroes.

New Eyepiece from TeleVue

We've had our first delivery of TeleVue's new Ethos 13mm eyepiece with a hundred-degree apparent field of view and we've sold out already. It really is a very impressive eyepiece and gives a view that has to be seen to be appreciated. The next delivery is on its way so why not order yours now? Failing that, put it on your Christmas wish list, you never know your luck.

Astronomy Opportunities in America

Regular readers will be aware of the house I rent out to astronomers and bird watchers at the Arizona Sky Village where the skies are clear and dark and the wildlife is abundant. Now one of our long-time customers, Chris Traher, has established a different operation in New Mexico where you can set up your own remote observatory or install your telescope in one of his. If you'd like to find out more about Chris' venture please call me at Green Witch and I'll pass on his contact details.

Meanwhile, the house continues to be very popular and we're getting quite a lot of repeat business from visitors who enjoyed it so much they're going back for more.

Mars is back

It won't be at opposition until December but Mars is getting close enough for good quality images to be taken. Ralph brought in a series of four he'd taken through his ten-inch Orion Optics reflector with a web cam and they are quite detailed. If you have a web cam or are planning to use one for astronomy then why not practice now on Mars ready for closest approach.

Star Parties

We always hold a star party on Halloween to celebrate the birth of Green Witch so we shall be holding one at the showroom on Wednesday 31st October. All are welcome and the showroom will stay open from 10 am until the party ends. The party itself will run from 7 pm to 9 pm and we shall have telescopes and binoculars outside for you to use plus the usual experts on hand to guide you round the sky. If the weather doesn't cooperate we plan to hold a workshop inside covering some aspect of astronomy yet to be decided.

As last year we plan to run star parties on alternate Tuesdays until Christmas. The fomat will be the same as for the Halloween Party and each time we shall cover a different theme, such as the Moon, Nebulae and Star Clusters. The first party will be on Tuesday 6th November. Don't forget that the showroom will be open throughout and we suggest you arrive before 7 pm if you want to discuss anything individually.

Astronomy for Absolute Beginners

We're running one more of Jeffrey's very popular courses for beginners on Saturday 20th October 2007. The course really is designed for absolute beginners and gives a good introduction and overview that will give newcomers a good start to the hobby.

If your interest is in learning more about the practical aspects of using a telescope then one of Lee's courses may be more suitable for you. We're planning to hold a couple before Christmas, one on general astronomy and the other on astrophotography. Details, dates and times will be posted on the web site shortly.

Dark Sky Symposium in Bled - 6th-7th October 2007

Unfortunately I shan't be able to attend this symposium as I've been away quite a lot already this year but I do recommend it for anyone interested in the subject and/or who fancies a weekend at a beautiful lakeside resort in the Slovenian mountains. Details are at http://www.darksky2007.si/ I believe that last-minute bookings are still available.

Bedford Astronomical Society 20th Anniversary -  Sunday 7th October 2007

Congratulations to Bedford Astronomical Society who are celebrating their 20th year of operation. To mark the occasion they have organised a day of astronomy talks and other activities at Bedford School from 9 am to 5:30 pm. Programme details can be found on their web site at http://www.bedsastro.org.uk/ and they have a good lineup of speakers.

Lee will be there with a Green Witch trade stand so if you plan to be there and want him to bring something specific please call him on 01954 211288.

Meanwhile...

Wendy and I plan to visit one of our suppliers on the same day to look at new telescopes and accessories that they will soon be bringing into the UK. We'll let you know how we get on.

Looking South at 10 pm

The view tonight will be somewhat limited by the bright Moon and our southern meridian falls between the Summer triangle and Pegasus, running through an area with few major and distinctive shapes.

Notice how far the Summer Triangle has moved to the right since the last newsletter, providing us with yet another reminder of how quickly time passes. The Milky Way has also moved to our right but won't be visible in the moonlit sky.

Nevertheless there are several objects of interest on the southern meridian which are worth seeking out, even if you have to wait a few days for the Moon to move away. Almost exactly due south at 10 pm is the giant planet Neptune. It is in the constellation of Capricornus about 23 degrees above the horizon and has a magnitude of 7.8 making it a feasible target for beginners but you will need binoculars at least to see it. If you want to look for it then use one of the planetarium programs to generate a finder chart. It is less than three arc-seconds across so you will only see it as a point of light but if you do find it you'll have the satisfaction of seeing the solar system's most distant planet (with apologies to Pluto and all who still consider it to be a planet).

With the Milky Way off to our right we are looking at the area outside our galaxy where globular clusters exist. These contain some of the oldest stars gathered together in close proximity to each other. Working from top to bottom we have M15 in Pegasus close to the border with Equuleus, M2 in Aquarius and M30 in Capricornus. All are best seen in dark skies and require a telescope. Even a small one will show them but a larger one is needed to resolve any stars.

And finally...

Although the Royal Greenwich Observatory was closed in 1998 its spirit lives on and former staff and friends are meeting at Herstmonceux Castle on Sunday for an afternoon of catching up on old friends and enjoying our former home. Sir Patrick Moore who suggested forming the RGO Society will be there if his health permits.

Looking through the list of attendees reminds me what a wealth of talent the RGO had and how sad it is that this organisation which was the envy of the world should have been so carelessly tossed away.

Clear Skies and Best Wishes

Neil