Saturday, February 04, 2006

The art of "seeing"

Tonight I learned what it really means to have good "seeing". Astronomers use the term "seeing" to define the stability of atmospheric conditions which can be effected by moisture in the air, heat shimmer, and the transparency of the atmosphere. All these factors combine to either give you a crisp and sharp image through your eye piece on nights of good seeing or on bad nights of seeing a fuzzy, wobbly and shimmering image which never wants to settle or come to a sharp focus. For the last two years since I bought my Meade ETX105 telescope I've read a lot about seeing conditions and I've even thought that on a few nights I have had good seeing conditions. This was until tonight when I set up my telescope after many weeks of grey and overcast skies. I've never experienced such stunning seeing conditions! Usually with my telescope, the 105mm aperture normally allows me to use a 4x Barlow with at most a 20mm lens. Any more magnification and the image would become blurred and dim. Tonight however, I put the 20mm lens in and noticed that the image was particularly sharp and steady. This got me thinking and so I popped back indoor and pulled out the 15mm lens and placed it in to the 4x Barlow. To my utter surprise the image of Saturn I was looking at previously with the 20mm lens just jumped out at me as crisp as anything. Moments like this usually cause amateur astronomers the world over to start frothing at the side of their mouths and whispering quiet expletives of wonderment. I shall not reveal which of these I was doing at this point in time. I stayed at the eye piece for a good fifteen minutes and gazed at this immensely brilliant site of Saturn and congratulated my little ETX telescope for exceeding all expectations. I thought I'd push my luck and swap the lens out for a 12.4mm lens. This I knew was pushing the telescope beyond its acceptable maximum limit of magnification but I thought it was worth a look. Once again, rock steady; No shimmer and no blurring. I was amazed. Not only had I blown away the maximum practical limit of my telescope, but I had almost perfect seeing conditions and I could clearly make out the Cassini division and faint banding on the atmosphere of Saturn. There was even a hint of the typical creamish yellow colour one often sees in high quality photographs of Saturn. I've not really managed to observe such detail in the past. The best I've managed to achieve whilst visually observing Saturn is to make out the rings and observe a very bright and washed out planetary disk.

The Meade 105 telescope constantly surprises me and tonight I saw first hand how and why this small telescope can match and out perform other much bigger aperture telescopes. I've often read such claims about the Meade ETX series from other observers but until tonight I had never experienced this superiority myself. Nights of such good seeing are rare but when they do happen, boy is it good. Strangely enough, tonight wasn't the clearest of nights. There was broken cloud dotted around here and there which kept obscuring Saturn on many occasions. I'd be really interested to hear from others who might have had good seeing tonight, especially around the area of North West London at about 21:35 UT.

Today was the second day of the European Astrofest. I attended the whole event from the moment doors opened to the very last lecture presentation of the day. Talks were given by Robert Walsh from the University of Central Lancashire on understanding the Sun - a decade with SOHO, David Hughs from University of Sheffield talking about probing comets - Deep Impact and beyond, Nik Szymanek demonstrating some excellent image processing techniques using Adobe Photoshop, MaximDL, The NASA Fits plug-in for Photoshop and a number of other excellent freeware packages. Other talks were given by John Zarnecki from the Open University about the Titan and Cassini-Huygens mission, a superb talk on globular clusters and their evolution by Gerry Gilmore from the Institute of Astronomy - University of Cambridge and a fascinating talk on Black holes and wormholes by Jim Al-Khalili of University of Surrey.

At the show I picked up a superb 5mW green laser pointer from BCF, a really nicely made Hartman mask from Venturescopes and a camera adapter and eye piece projection piece again from BCF. The Starry Night stand was always very popular and they had the latest version of Starry Night Pro Plus on display with live demos being given to anyone and everyone. The Campaign for Dark Skies was out in force and ran an excellent raffle which managed to make over £600 for a good cause. I had a long and very informative chat with the guys from Starlight Xpress and did a compare and contrast with their CCD camera's and the SBIG series. I've still not decided which one is the better CCD camera but one thing I do know is that the Sony CCD chip used in the Starlight Xpress series of CCD camera's has about one tenth of the dark current of the SBIG Kodak CCD which apparently removes the requirement of taking a dark frame. Very interesting and also VERY expensive equipment! Starlight Express also had their active optics attachment on display which I noticed many members of the public incorrectly referred to as adaptive optics. Of course, actice and adaptive optics are two totally different things aimed at correcting different aspects of CCD imaging. Screen shot demonstrations of the active optics relay at work showing before-and-after examples were truly impressive. Finally, the British Astronomical Association and the Society for Popular Astronomy were both manning busy stands. I hope they both managed to sign of up plenty of new members. As I was leaving the exhibition I noticed a stand from UK-SEDS which managed to lure me to their stall with the offer of a free t-shirt if I signed up to join their "cause". What I discovered was that SEDS is the world's largest space enthusiast organisation for both school and university students. Anyone who is interested can become a member of UKSEDS, young or old, student or non-student. The organisation was founded in the US in 1980 by students at MIT and Princeton University and is continuing to grow, currently having more than 60 branches worldwide. UKSEDS was formed in 1988 and is one of the fastest growing national SEDS groups. Their five main aims are to promote the exploration of space, and the research and development of space-related technologies. Provide a forum through which students can become involved in the international space community. Motivate students to excel in space-related fields.
Share in the advancing knowledge and growing benefits to be reaped from space and improve space-related education through both academic work and hands-on projects. Yes I did join UKSEDs and yes I did get my t-shirt and a UKSEDs pen as well! Very nice chaps and I wish them success and hope to participate in their UK wide events.

Over-all, this was a thoroughly excellent European Astrofest for 2005. I look forward to next year’s event - hopefully at a bigger venue. The town hall in Kensington High Street is starting to get rather cramped. Wembley Conference Centre could make an excellent alternative as it's very easy to reach by public transport, has ample parking space and it very large.

The clouds have cleared, I think I'll get in another half an hour of observing and see if Saturn is still centred in my 12.4mm lens.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home