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Showing posts from November, 2019

How to use an intervalometer

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29 November 2019 The cheapest way of taking a photo through a telescope is using a mobile phone, normally stabilised using a phone adapter, such as the saxon ScopePix. This is a good start, but the next step in astrophotography is to use a DSLR. These attach to the business end of your scope using an adapter called a t-ring (this is a photo of mine). But then you've got a whole new set of problems. Every time you press the shutter button, you rock the scope slightly and it ruins the photo. And you want to take lots of photos so you can give them to your stacking software. And you don't want to be hovering over your rig all night, just pressing the button every minute or so. After all, we all need to sleep occasionally. What you need is a way of pressing the button without your having to actually be there. If only there were some gadget that does that for you. Of course there is, it's called an intervalometer, and it’s like an old cable release with a brain. Mo

Ny-Ålesund

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27 November 2019 You probably know that I'm a bit of a Nordophile. I lived in Norway for three years, but sadly never got to visit the archipelago of Svalbard up near the North Pole. This is, you may recall, the location of Brage Bærheim's astroterrestrial photo that I featured a while back. It seems there is a weak point (what that means I'm not sure) in the Earth's magnetic field near Ny-Ålesund, a settlement on the West side of Svalbard. During auroras, the solar wind gets in through this weak point and interacts with the atmosphere, ionising it and drawing some of it out into space along the magnetic field. A while back, scientists at Ny-Ålesund launched two sounding rockets into an aurora. They were able to take readings in a very narrow time period, and gathered data about what they call the "atmospheric fountain". That study is ongoing. However what they do know is that the amount of atmosphere lost into space is only a tiny proportion of th

Southern Hemisphere resources

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Astronomy is a popular pastime the world over. Because of this, there is a pile of information available for people like us to keep up-to-date with what's going on. For an annual guide, the ASV Astronomical Yearbook provides me a pile of information. Being the astrophotographer I'm always looking up rise and set times for the Moon. But there are other very useful and more regularly-updated resources. I get a daily email from EarthSky News, which updates me on anything topical. I also use SpaceWeather.com for solar and aurora updates and Heavens-above.com for satellite information. For maps, my go-to app is Stellarium. This shows me planets, other solar system objects, satellites, deep sky objects and a heap more. However, I was talking with an astronomer the other day, who said she was a bit dismayed at the lack of resources specifically for Southern-hemisphere residents. Most of the stuff we see is mainly for the Northern hemisphere. Because of the different angle, wh

Magnification from a telescope

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One of the most common questions clients ask us is how to get more magnification from a telescope. Just about everything optical these days comes with a zoom lens, so people think nothing of zooming in and out. So how do you do this with a telescope? Short answer: you change the eyepiece. Warning: I’m about to get a bit technical. I’ll use pictures to illustrate, but I won’t be offended if you don’t read on! All telescopes work in the same basic way. The main scope bends light into a focus, and then you use an eyepiece to look at that focus. The main scope might use a lens or a mirror, but the effect is the same – all the light squashed into a focus. The distance between a lens and its focus is called the focal length. The shorter the focal length, the more powerful the lens. Have a look at my little hand-drawn diagram. I’m starting to get a reputation for this .  Magnification of a telescope is given by the focal length of the objective (main) lens or mirror divided by the

Gariwerd hike with Emma

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I’m back in the shop after hiking in the Grampians with my daughter. The Grampians (or as it’s more properly known, Gariwerd) is a great place for a birdwatcher to spend time. We hiked the currently-open section of the Grampians Peaks Trail, a three-day loop that starts and ends in Halls Gap. We spent nights at Bugiga and Borough Huts. When the GPT is complete, it will have 12 campsites. I won’t belabour you with details of the hike itself, apart from saying it was tough in parts but memorable. Views from the western side of the valley were spectacular (as you can see in my phone photo), and it’s rare that you get to stand on the edge of a big cliff. Bugiga was especially cool. It’s a zero-contact eco camp, where you walk and camp entirely on boardwalks. Setting the tent up on a timber deck was a challenge, but our tent doesn’t need pegs, and we were able to fix our guy wires to a cable on the edge of the platform. But the birds were everywhere. Because it’s Spring, they may hav

Joanne Tucker's photos

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18 November 2019 One of the things I especially like writing about is the development of skills in this hobby. More than any other pastime, the demands of astrophotography - precision, care, understanding and patience - create a pathway where beginners develop into skilled users of the equipment. In particular, and I've mentioned this for others before - you don't need to have high-end equipment if your skill level is high. I met Joanne the other day when she came into the shop to upgrade an equatorial mount. She had a Sky-Watcher Star Discovery mount on which she could put either a 127 Maksutov or an Evoguide 50ED scope. This was what she was using for deep sky objects. I was impressed when Joanne told me she was getting photos using a goto alt-az mount, but you remember Josh Carnovale proved it was possible this year. But then she showed me the photos and I was stunned. These are next level stuff. She sent me some, and I said I'd publish three. I've attached

Voyager

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15 November 2019 Voices from interstellar space. Back in 1977, NASA launched the twin probes Voyager 1 and Voyager 2. Voyager 1 left the solar system in August 2012, and now, nearly 18 billion kilometres from the Earth, Voyager 2 has finally left as well. It's outside the "heliosphere", or the bubble of particles ejected from our Sun, and so is now in interstellar space. How can we tell that Voyager 2 has crossed the heliosphere? The probe has a few sensors that are still working. These can measure the temperature, pressure and density of plasma particles blown out of the Sun. Scientists at NASA describe the plasma inside the heliosphere as "solar wind" and the particles outside as the "galactic wind". The characteristics of these winds are different. Voyager 2's measurements all fell significantly in around November 2018, and levels have remained low. This indicates that it wasn't just a random zone of low plasma density, but Voyager

Colour fringing

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Ever wondered how refractor telescopes deal with colour fringing? The other day I pulled apart a telescope lens cell. Here's what I found. Because we service telescopes, occasionally we get patients which are, sadly, unsalvageable. This one was one of those, an entry-level refractor with a terminally mangled focuser. I took the opportunity to pull the front lens off and see how it worked. The telescope is (was?) a doublet-type refractor, meaning there are actually two lenses at the front, built especially to refract blue and red light to the same point. Single lenses refract blue closest to the lens, green in the middle and red furthest away. This is the dreaded "chromatic aberration" that refractors produce. Visually, it's not much of a problem, but taking a photo with this type of lens looks ugly. Check out my photo of the Southern Cross. See the blueish purple fringes around the brighter stars? That's what happens when most of the light is in focus, but th

ASIair

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6 November 2019 Ever since autoguiding has been an affordable thing, really good astrophotographic images have been easier and easier to get. So what is that? Autoguiding is when you connect a second scope (normally something inexpensive) and a camera to your main scope. This takes photos of stars and sends them to a laptop, which locks onto a star. If the computer sees the guide star wandering even a tiny bit,   it sends correcting information back to the mount. Using autoguiding, as long as you've aligned your mount accurately, you can confidently move from 30 second exposures with nice round stars to 30 minute exposures or more. What's the downside? Urrgh, cables! Until I did some serious cable management, you could hardly see my scope under the cables. It looked like a plate of spaghetti. What's worse, they drag on the ground and catch on things as your mount tracks during the night. Nothing ruins a nice shot as effectively as a snagged cable. Enter the