Showing posts from April, 2019

Little Corellas on my street

1 May 2019 At this time of year, Little Corellas form large flocks (of maybe a thousand birds) and roam Melbourne for seeds. Liquidambar trees are among their favourite targets. We have a mature Liquidambar up the side of our place in East Kew. So of course, we got targeted. I do love Corellas. Their yelping, slightly whingy call is quite unique (unless you're comparing it with Long-billed Corellas, of course). All we could hear for a while was the birds calling and the banging of the seed balls hitting our neighbour's roof. I grabbed my ScopePix, attached it to my Nikon Monarch 8.5x56 binoculars and went out for a look. The saxon ScopePix is really useful for this kind of thing. It takes a bit of practice to get it square on, and it depends on your binocular's eye relief how far you set it back from the eyepiece, but once it's aligned it's brilliant. The way I use it is I attach it to the right barrel of my bins and use my right eye to look through the

Astroterrestrial photos from Acraman

29 April 2019 Some more astroterrestrial photographs. All of this you can do yourself. All I used was a DSLR and a fish-eye lens on a tripod. I didn't do any tracking, so the stars are very slightly trailing. Building on the posts from a couple of weeks back, I tried to put the theory into practice. The first photo is taken from Spear Creek near Port Augusta. It was about 3am on the 10th of April, so the Moon had set and the bow of the Milky Way was very high. This is a 30s single exposure at f/3.5, ISO 6400, and I pushed the levels around in Photoshop a bit - not too much. The bright object is Jupiter and above that, next to Antares, you can just make out the dust lanes of Rho Ophiuchi. Now the bad bit: it was a windy night and my light painting was not good. I used an LED torch, and went back over the tree on the right a second time. You can see the tree had moved in the wind, giving an irritating double exposure. The second photo was a test shot at Acraman Bore. I was

Little Crow

26 April 2019 How well do you know your Corvids? An amateur geologist friend and I had spent a few days at Acraman Bore in outback South Australia, checking out Australia's largest meteorite crater as well as the surrounding country. After Dean and I struggled off Lake Everard sheep station, we arrived at our next campsite in Woomera. Around the campground we could hear two types of Corvids, Australian Ravens and Little Crows. Now, you'll probably know that most Australian Corvids are very similar-looking birds. Get them in your binoculars and they're large black glossy birds with heavy black bills. Real experts like Dean's wife Marilyn can point out the subtle field marks that diagnose the bird, like beard size, wing shape and movements. I'm not that much of a gun birder, apart from knowing one field mark, which I'll get to. The saving grace is the Corvids' calls. They're all pretty distinctive. The Australian Raven has a very memorable wail

Occultation of Propus

24 April 2019 Occultation of Propus ( η Geminorum), 11 April 2019, 21:32 (ACST)   This was a totally unexpected happening. Dean and I had made camp at Acraman Bore (with the permission of the station manager, of course). We were relaxing after dinner, and watching The Emu come out to our south. I was using my binoculars to wander around the sky when I noticed the Moon was especially close to a reasonably bright star. Were we were going to see an occultation? An occultation is when the Moon moves in front of a star. It actually happens all the time, but it's hard to see unless it's a bright star, as the Moon blots out everything around it. But usefully, when the Moon is a crescent, it has dimly lit side. This dim light is reflected off the Earth, and you can see stars right up to this side. Interestingly, this means that occultations normally only happen in the week or more prior to the full moon, as during this time the Moon appears to move towards its dim side. After t

Bill's Outback Rho

22 April 2019 You can do this! Here's a photo I've brought home from outback South Australia. It's Rho Ophiuchi, taken using a Pentax K3-II and an ancient Takumar 85mm f/1.8 screw-mount lens built in about 1972. Rho Ophiuchi is one of those parts of the sky that everyone wants to photograph, a bit like the Great Nebula in Orion. It's not easy, though, mainly because it's so big, but also because you need a seriously dark sky. The second part we had. Wow. Absolutely zero light pollution - the closest electric light was over 32km away. At 2:45am on the 12th of April the moon had set and the sky was alive. Using averted vision, you could actually see the dust lanes of Rho Oph without any aid. These dust lanes are incredible. My photo shows them to an extent, but with a 20 second exposure it's never going to be fantastic. A better result would have needed a more time, say 3-5 minutes, which in turn would have required a tracking mount, such as a Sky-Watche

Dates of Easter

19 April 2019 Happy Easter - or today I should say, Happy Good Friday. Just a quick one while I process some photos after my outback trip. The date of Easter Sunday. Easter Sunday is defined as being the first Sunday after the full moon that follows the March Equinox. That was defined ages ago - in AD 325 by the Council of Nicaea. This was an early Christian conference in what is now Iznik in Turkey. But, as always, things get complicated. (Am I allowed to say that the Devil is in the detail when it comes to things Ecclesiastical?) The site (one of my favourites) tells me that the March Equinox was at 21:58 UTC on 20 March. The first full Moon after that was at 01:43 on the 21st - only a few hours later. The first Sunday after that was the 24th of March, so that's Easter Sunday, right? Clearly not. For the Ecclesiastical calculations, when the full Moon happens on the same day as the Equinox, so the first full Moon AFTER the 2019 Equinox is on t

Space Junk

17 April 2019 You might remember a few weeks ago I was talking about space junk? I included a photo of a chip taken out of one of the windows of the International Space Station. This was caused by a tiny flake of something (they think it might have been paint) that struck at about 26,000 kilometers per hour. Well, in more recent news, India has demonstrated that it's now the fourth nation that has the ability to shoot down a satellite in low Earth orbit. They did this using a kinetic strike, which is also known as "hit to kill". Simply put, all this involved was a well-aimed rocket that collided with the satellite, blasting it to pieces. Sounds familiar? Hit-to-kill strikes are the same as any other collision, and are a source of dangerous space junk. According to the US Air Force Space Command, India's demonstration created more than 250 (some say 400, but it depends on the size we're tracking) pieces of dangerous space junk in low Earth orbit - which i

Astroterrestrial photography

This is a slightly longer post than normal, being made up of four individual posts. Astroterrestrial photography The three elements 8 April 2019 This photo of "the Emu" (the Indigenous name for the Milky Way in the area of the Southern Cross) was taken three years ago today. My octogenarian father had come up to Wyperfeld NP with me for a couple of days. I was after Jupiter as well as some birds. He wanted to see the place again and, I think, to spend some time with me, which I appreciated. This is what I call an astroterrestrial photo. That is, it is a combination of astronomical and terrestrial imaging. It's by no means perfect, but photos can be very evocative and I like the feeling this photo gives me. It helps me remember the evening. My father is sitting in a folding chair, with a few bits and pieces around him. A large subject in this type of photo, like a tree or a lighthouse, gets a lonely quality, as though it's alone in the universe. In turn, having a s

Video: types of telescopes

6 April 2019 Bill has made a new video , and it's now on our YouTube channel . It's an animation showing the four main types of telescopes we deal with here, a bit of their history, ray diagrams of how they work, and what their best uses are. Bill's been working here for a little while, and his workmates are starting to get the impression he's a little ... unusual. Watch the video and see if you agree.  

Cruithne observation

5 April 2019 Last time, I talked about Cruithne, and what a weird thing it was. From the Earth, it looks as though it orbits the Earth in a horseshoe shape, going one way around, stopping, then going back the other way. It’s explainable if you look from a different perspective, because the Earth and Cruithne both orbit the Sun in the same period of time. It’s just that it looks like some bizarre orbit from the Earth. I also said that if you've got access to a large telescope you'd be able to see Cruithne - just. When I said "just", I really mean it. This is a magnitude 17-18 object, so it's incredibly dim. My low-magnification rig has imaged down to magnitude 14, when I got a photo of Uranus' moons Titania and Oberon. This was a 10 second exposure, so I'm thinking it's worth a try. Those of you with larger-aperture rigs should be able to do this. Of course, the alternative is to join the Astronomical Society of Victoria and use their equipment. A 44 in


3 April 2019 One of the things that I’ve seen on QI a couple of times now is “how many satellites does the Earth have”? It’s a trick question. “Satellites” has a couple of different definitions. But the thing I did find interesting was when they started talking about something called 3753 Cruithne.  Pronounced Crew-EEN-ya, it’s a chunk of rock about 5 kilometres across, that orbits – well, it’s not really clear what it orbits. If you’re on Earth, it looks like it’s orbiting Earth. But from other perspectives, it looks it’s orbiting the Sun. But it gets weirder than that. If you’re on the Earth, it looks as though Cruithne goes around the Earth in a horseshoe-shaped orbit. Yes, that’s right, it seems to orbit us, approach, but then slow down and fall behind. But before the Earth catches Cruithne again, it speeds up and pulls away. I mean, what the…? It’s not that Cruithne follows the Earth around the Sun. If you looked down on the Solar System from way above the sun, you would see that