Showing posts from May, 2020

Heat haze and what it can do to your views

People often ask me why the magnification on terrestrial telescopes is lower than on astronomical telescopes. It's because the atmosphere does horrible things to light rays. Have you ever tried looking at something on the ground with a high-magnification telescope, especially on a warm afternoon in summer? You're unlikely to see much at all. Here's a photograph of an aeroplane taking off. It was taken by my mate Paul, and I've shown some of his images before. Notice the trees in the background under the wing on the right? They're pretty clear. However, the trees that should be visible to the left through the jet engine exhaust are very blurred. Air isn't a smooth, consistent medium. It has warm and cold pockets, which act as lenses and distort light passing through. These move around chaotically, and the effect is what we call heat haze. When you magnify the image it becomes quite obvious, with the image moving about. The more magnification, the more obvious it

Recording bird calls using sonograms

Knowing bird calls is important Some birders just seem to be able to come up with the name of a bird simply by hearing the call. Even more impressively, they say things like "there's a Musk Lorikeet inamongst the Rainbows". In a situation like this, my reaction is to ask "how do you know? What does that call sound like? I can hear dozens of birds, what am I listening for?" Remembering bird calls is a huge part of birding. Certainly, a good knowledge of calls is crucial to identifying what birds are around you. Let's say I'm out in the field, after a particular target bird. I can play the call (without disturbing the bird), and that'll stick in my mind for a while. But how can I remember it permanently? But how can you do it? My mate Peter with a shotgun mic For me, taking field notes about what I see is a big help. Particularly as a newer birder, I took lots of notes about what I could see - the colours, patterns, even behaviour of the birds. That w

Exoplanet round Proxima

Back in December 2018, I wrote about the trinary star system of Alpha Centauri (see photo). The star you can't see, Alpha Centauri C, is a bit overlooked, even though it's the closest star to the Earth (apart from the Sun, of course). It's more commonly known as Proxima Centauri. A few years ago, scientists found evidence for a planet orbiting Proxima. They think it's about earth-sized, and in an orbit that would support liquid water. Planets are typically named after the star they orbit. The star itself is given the suffix "a", and so the first planet discovered has been named Proxima Centauri b. Of course, if Proxima is more properly called Alpha Centauri C, then shouldn't the planet really be called Alpha Centauri C a? All that aside, researchers now have evidence that there may be a second planet in orbit around Proxima. We'll call this Proxima Centauri c. There are a few ways of finding exoplanets. A lot are discovered using changes in luminance r


You probably all know that one of my pet hates is unnecessary hype.  I hate clickbait headlines on news sites that ask really big questions, campaigns that create a nonexistent problem which is miraculously solved by the product (look up the origin of the word "halitosis"), "real" ingredients (as against imaginary ones) or ingredients that the product is “free of”, but wouldn't have been used anyway. Yes, you can call me "Princess Rantipants".  But on to today’s hype: the "supermoon". Recently, we had yet another one. You probably know that the Moon goes from perigee (when it's closest to the Earth) to apogee (when it's furthest away) each orbit. The orbit itself is nearly round, so the difference isn't much - something like 7 per cent from average to largest. You probably wouldn't notice without measuring. Supermoons happen when a full moon coincides with a perigee, so the moon is full, big and bright. But there's no agre

My messy study

OK, here's a bit of fun for the lockdown. Recently, the Guardian newspaper ran a story on people who work from home . The specific angle was the embarrassing difference between what colleagues see - the camera's perspective - and what a visitor to the house might see. The article included pictures confessing both perspectives. I looked at this article and gazed abashed around my study. It seems that I'm one of those people too. My daughter and I run the local Joeys mob - Scouts under the age of 8. With Coronavirus having closed schools, Scouts Victoria has suspended face-to-face meetings in halls. As a result, we're using Zoom, a teleconferencing program, to carry on with our Joey meetings. We normally present the meeting from the spare bed and have the computer and its camera set up on a small table in front of us. That way we have a very sparse background with only an Australian flag. You can see the Zoom picture of me here. It's not the best quality picture, take

Photographing an asteroid - failure and success

What's this mess? I took this disaster of a photo while looking (in vain) for a passing asteroid. A few days ago, it was a clear night in Melbourne. I took the opportunity to go out into the back yard and do some photography - as you do. What I was after was the Statue of Liberty nebula. ( I eventually posted it alongside a more concrete Statue of Liberty .) However, I'd heard about a close pass of an asteroid that was coming up, and thought I might be able to get a photo. The asteroid's name was (52768) 1998 OR2. Clearly a family name. From what I can gather, it's an egg shape, roughly 2km by 5km. That's big, and if it collided with the Earth it'd cause a heap of problems, but it wasn't coming closer than 16 times the distance of the Moon. It's also not a giant: the Chicxulub asteroid was up to 80km across. But it's large enough to be spotted with an 8-inch telescope. Mine is only a little more than half that, but I thought I'd have a stab in th