Easy for some

It is just not fair. Some lucky people get to go to the VLA for a 'summer school'. At least they have to do lots of hard work - doh! Seeing some infra-red heaters to dry the front of the receivers gives me some ideas though!

Posted in astro blog by Stuart on Sunday 27th Jun 2004 (23:18 UTC) | Permalink

Sucker Holes

I've been without both an internet connection and - even more importantly - a power supply for my computer, since Friday night so have been unable to add anything here until now.

On Friday night we decided to make a two dimensional map of 3C 345; a quasar which is very compact compared to the resolution we have. Ideally the map should look very boring with just a 'dot' in the middle but in reality our 'beam' will add some extra features - think of it like imperfect eyesight.

At the frequency we use, we are susceptible to water vapour so when some comes by, it makes our signal go crazy. Unfortunately this is what happened on Friday night. What was most annoying was that there would be clear patches when we would think it was safe to start and then once we had, it would get bad again. A variation of Murphy's Law, these are usually called "sucker holes" in optical astronomy; you are a sucker to think the weather might be improving only for it to cloud over again. By 1am we finally decided that it was hopeless so went to bed.

Posted in astro blog by Stuart on Sunday 27th Jun 2004 (22:39 UTC) | Permalink

Sound of the Universe

This month seems to have become a repeat of last November. Not only have we had an article saying that Jodrell is doomed, we have now got another sound file of the cosmic microwave background. However Prof Mark Whittle, who created the sounds using software like CMBFast, thinks that nobody has done it before. He does have a good (long) description of what the CMB is though.

"I have to say that the Universe is a lousy musical instrument," said Mark.

Posted in astro blog by Stuart on Thursday 24th Jun 2004 (10:21 UTC) | Permalink

SOHO and Venus

ESA/NASA's Solar Heliospheric Observatory (SOHO) didn't see the transit as it was in the wrong place. It is at a special point in space called L1 which is where the gravity of the Earth and Sun balance. However it doesn't sit at this point but orbits it. Unfortunately, from the position it was in last Tuesday, Venus appeared to be below the Sun. However the solar physicists have been able to check several of the instruments by watching Venus against the corona.

If you're quick you will still be able to see Venus in the images from the LASCO C3 instrument.

Posted in astro blog by Stuart on Saturday 12th Jun 2004 (01:23 UTC) | Permalink

Google Transit

Nice to see that Google had a special transit logo yesterday.

Posted in astro blog by Stuart on Wednesday 09th Jun 2004 (14:15 UTC) | Permalink

Bad AU

Yesterday, the Open University's Stardate programme attempted to involve the British public in a large experiment to calculate the distance of the Sun by using times for third contact. Unfortunately, their final value was about 161 million km, or about 10 million kilometres too much - note that although the Sun's average distance is 149.6 million km, the Earth moves in an ellipse so is sometimes closer or further away.

So what caused the discrepancy? As the only distribution of times I saw was a very brief, poor resolution plot on the TV, it is difficult to say. The biggest problem may be that nobody had synchronised their clocks before taking measurements so people may have measured to the nearest second but that second could have been a minute or so out! Or as Brian Campbell points out in the StarDate forum, it might be because the TV viewers might have used the time for the Egyptian camera, although I think that is probably taken into account when you enter your numbers as it checks how you did the observation.

Another explanation could be due to different filters being used. We noticed yesterday that third and fourth contacts happened later in our H alpha telescope images than in images taken using a white light filter. This could also be seen in the TV images as third contact happened later on the Egyptian images (which looked like they were in H alpha) than Adam Hart-Davis (the presenter) was saying from the Royal Greenwich Observatory images.

The H alpha filter only lets through a very particular part of the spectrum - red light at a wavelength of 656.3 nanometres. At this colour, you actually see out into the chromosphere of the Sun which is about 2500km thick. As Venus is about 1/3 the distance to the Sun, this is equivalent to about 800km at Venus. The planet is about the same size as the Earth at 12400 km so this is about about 15.5 times less than the diameter. The time between third and fourth contacts was about 19 minutes so a 15.5th of that is about 1.2 minutes i.e. because you can see the chromosphere with the H alpha filter, you get an extra 1.2 minutes of transit! This agrees quite well with what we saw yesterday. Putting in a later time for third contact will cause the distance of the Sun to be artifically increased.

I wonder what filter the OU were using to measure the second contact with? If they used a H alpha filter they would start the transit an extra 1.2 minutes as well giving a possible increase of 2.4 minutes overall!

Posted in astro blog by Stuart on Wednesday 09th Jun 2004 (14:06 UTC) | Permalink

Transit of Venus

Well it finally happened! All that waiting and planning finally payed off and we managed to see pretty much all the transit apart from the odd cloudy patch near the beginning.

Preparations were started a couple of months ago and I produced the Jodrell Transit microsite to provide information about the transit in advance. Yesterday I sorted out a real time display to be projected on the big screen in the Visitor's Centre which had NASA TV, various webcams from around the world and the Jodrell Bank webcam using the Coronado Helios I telescope. It also had a Venus transit fact ticker like those you get on 24 hour news channels!

A lot of people turned up and it was a very good morning. There were loads of people from Macclesfield Astronomical Society and some from the West Didsbury Astronomical Society. Many of them very nicely provided me with digital photographs all morning so that I could display them on the website as the transit was happening. I ran around with a laptop and a memory card reader grabbing lots of very impressive images of the transit and had to find network cables to connect to - we don't have wireless networks at a radio observatory!

We also got a visit from Fred the Granada weatherman who was really excited by the whole thing. He even managed to get a fairly long piece on the Granada news filmed live at about 6.30pm from the roof.

A great day although I am now very tired having not got much sleep last night!

Posted in astro blog by Stuart on Tuesday 08th Jun 2004 (18:37 UTC) | Permalink

Jodrell in the news

I am in Oban on the west coast of Scotland sitting in an Internet cafe. I've been up mountains every day since Saturday and yesterday went up Ben Nevis for the first time. Today is an off day and I managed to buy the newspaper as the Guardian has a science section on a Thursday.

What a suprise when I discovered Jodrell Bank on the front page of the Life section. The article seemed to be partly critical of Jodrell Bank implying that it is at the centre of a controversy in astronomy. It seems to imply that the upgrade of MERLIN (Multi-Element Radio Linked Interferometer Network) to eMERLIN is an unecessary cost and that it won't contribute much. It mentions that the US upgrades (eVLA etc.) will happen around 2009 and that this will be the end of Jodrell - I would say they were complementary. It also mentions the SKA (Square Kilometre Array) but completely forgets to mention that Jodrell is pretty much leading the way for the UK in SKA involvement. From what I hear on my email, it has been causing suprise at Jodrell as the whole article implies the observatory is on its last legs. Why must national newspapers always insist that Jodrell is about to close?

For interest, the large photo used in the main article seems to have been taken from the other side of the Manchester-Crewe line in what is a farmer's field. I hope they got permission!

Posted in astro blog by Stuart on Thursday 03rd Jun 2004 (15:30 UTC) | Permalink
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