10th May 2017
Andrew said that next week we have Dr Louise Alexander with a talk about the history of the Solar System using lunar samples. Plus the internet links are now on our website.
Gerald said that he would be here at 19.00 with our solar scope to have a look at the Sun.
Andrew got us started with tonight's entertainment which is:
Astronomers´ Question Time
Ted started us off with a question about whether increased solar activity meant there would be an auroral display. Peter said there were a number of good sites that gave quite accurate information on the phenomena. He also took the opportunity to talk about Noctiluscent Clouds which can be visible in the Northern skies well after sunset in summer.
Jack said he had acquired a set of Vixen 2.1 X 42 low power wide field bins - he said they were great for looking at the Milky Way. He said the literature described them as using Galilean Optics - What were they? It was explained by Ron that this was a simple system that used convex and concave lens to provide an erect image and low magnification. Jack said they were listed at £259 he got his second hand for £150.
Peter said that because he had poor vision in one eye and found most bins impossible to use. Other also reported the same problem. I reported that a friend had a pair of German bins that did not require focusing perhaps they would resolve the matter. Ken said he had Glaucoma and that the test for driving which was to read a number plate at 25 yards did not apply any more he had to get examined by an optician.
Gord asked a tongue-in-cheek question - Why do we need to focus at all and continually readjust? There was a general discussion about how temperature can affect focus but that the atmosphere was the main cause. Larger professional scopes use adaptive optics to continually adjust the focus and gain that precise image. It was also mentioned that long focus refractors are less affected so it would appear to be a depth of field issue.
Jack asked why the collimation of his spectroscope changes. Possibly because of temperature changes as it had an aluminium tube.
The HST although it had its own very serious focusing issues at first it does not suffer from this problem as it is above the atmosphere. When the James Webb scope gets going it will be placed at the Earth´s Le Grange point behind the Earth relative to the Sun.
Gord asked why would the ISS ever have to be finished - surely it is of immense value to humanity. If/when its useful life comes to an end although it can be kept in position quite cheaply there would be an ongoing risk that something would happen and it might come down out of control and cause a disaster.
Cosmin asked how he should take astronomical images - he was specifically concerned as he had heard talk at the club that a camera needed to be modified. It was quickly established that any camera or phone could take an image through a scope without modification. The removal of the red filter in expensive cameras was to allow long exposures to be made of deep sky objects. Ordinary cameras that had manual controls of exposure were perfectly capable of taking excellent images.
Emma´s assistant asked where he should look for the source of the Big Bang. The strange answer is everywhere.
He also wanted to know you cannot hear in space. This is simply because there is no air to carry the sound wave.
Cosmin said he understood we only see the Universe because light reaches us from it. The strange thing is we now know the universe is expanding at an ever increasing rate so we must anticipate that eventually the stars will go out or be too far away for the light to reach us their speed increases.
Always amazing how the discussion flows with a gathering of intelligent folk pondering apparently simple questions.