Microsoft virtual telescope to be launched, 27 Feb
19 Feb at 23:11 by Wilson
Techcrunch is reporting that Microsoft is expected to launch a “virtual planetarium” application later this month, on 27 February (probably 28 February for those of us in Australia), during this year’s TED Conference. Under the name WorldWide Telescope, it is reported to be significantly better than Stellarium, the very useful open source application that transforms your PC in a planetarium.
Still according to Techcrunch, MS will display data from the Hubble Space Telescope and ten other Earth-based observatories, and the user will be able to view the sky in a range of different frequencies.
I will definitely be trying this out, and I’ll write a bit more once I’ve seen the product.
Comments OffContinue Reading
The great comet of 2007
15 Jan at 13:28 by Wilson
I went out last night to watch the sunset by the shore of Port Phillip Bay (the best place for an unobstructed horizon around here) and to try to see comet 2006 P/1 (McNaught). The picture you see here was not, alas, taken by me, but by a photographer in Austria. There was way too much glare in the sky due to high-altitude haze yesterday, and there were clouds obscuring the horizon as well. It was a long shot, anyway, as the comet was just one degree away from the Sun.
Today would supposedly be a better day for seeing it from here, as it will be several degrees above the horizon at sunset. However, the day is not only cloudy but also seriously smoky, and I don’t think anything will be visible at all; even the Sun is barely visible…
Our northern hemisphere colleagues certainly had quite a spectacle in the last few days, with the comet being clearly visible even during the day and being significantly brighter than Venus during the weekend; there are several amazing pictures all over the net, with a nice gallery at Space Weather.
The comet has already started to move away from the Sun and it will lose brightness very quickly; it will probably still be visible to the naked eye for a week or so, and it should be easy to spot from southern hemisphere locations (at least from locations without as much smoke in the air as Melbourne…), although possibly not in the middle of the day without binoculars (and, if you use binoculars, be very, very careful to avoid the Sun; make sure that you are in the shadow of a building and that there is no chance at all of accidentally looking at the Sun). I’ll keep an eye on the sky and will try to get pictures, if possible.
For observations over the next few days, from Melbourne, it will be visible before sunrise starting from the 19th towards the south-east; this image shows the position of the comet at 6am, as seen from Melbourne, for the next 30 days. The sun is rising after 6:15am on all those days.
In the evening, it is setting after the Sun starting from last Saturday (the 13th), and will be 10 degrees above the horizon at sunset on Wednesday (17th), a bit to the left of the Sun; that will probably be the best day to see it from here, as it should still be quite bright. The sun sets at 20:43 (summer time) on that day. The weather forecast for Wednesday is talking about a thunderstorm late in the afternoon, though…
It might be interesting to note that this comet was discovered by an Australian astronomer, Robert McNaught, on August 7 last year while working at the Siding Spring Observatory near Coonabarabran, NSW.
Comments OffContinue Reading
What’s up in 2007
20 Dec at 15:53 by Wilson
A great resource for any amateur astronomer (or, in fact, anyone interested in looking at the sky): Universe Today has a freely downloadable book listing interesting sky phenomena for each day of the year.
The book is richly illustrated (which accounts for the large file size, just over 23MB) and filled with historical information and observing information. You can download the book from Universe Today, or you can get a printed copy from lulu.com.
Comments OffContinue Reading
NAGging
5 Oct at 12:56 by Wilson
Last night was this month’s meeting of the NAG, about which I wrote here. Differently from the other months, this meeting did not have a theme; it was the “nothing in particular” meeting.
Because of that, we spent most of the time outside, enjoying one of the few clear nights of the last few weeks. Unfortunately, the almost-full moon made sure that the only “interesting” thing to look at was, well, the moon (note to self: looking at the full moon with binoculars after allowing your eyes to adapt to the dark will ruin your night vision for several minutes).
There were a few small telescopes around, plus the ASV’s large 20-inch; plus, several people (myself included) had their binoculars at hand. The only visible planet was Jupiter, but it was very low in the sky and it dropped off behind the trees before the 20-inch was set-up (and cooled down). Uranus and Neptune were up as well, but in the same general direction of the moon and, therefore, not visible.
One highlight of the night was seeing the ISS; it showed up low in the southwestern sky and disappeared when it was starting to set in the northeast, after flying almost directly above us and staying clearly visible (as a bright orange dot) for over two minutes. This was quickly followed by a 0-magnitude Iridium flare, followed soon after by a spectacular -3-magnitude one, with an unknown satellite doing approximately the same path of the ISS minutes later. It’s definitely getting crowded up there. (heavens-above.com will tell you when the ISS and Iridium flares are visible from your location, and how to find them)
What are Iridium flares?
Satellite flares, in general, are bright flashes of light visible from the ground when the Sun light reflects off satellites flying above. The Iridium phone satellites, in particular, generate very bright flares due to their format; the flashes can go up to magnitude -8, and can be visible in bright daylight if you know where to look at. Flares are very localised events; the “spot” of light created on the ground is some 10km wide, so you need to know your location (latitude/longitude) failry precisely in order to find out about them. Google Maps can help with that.
Comments OffContinue Reading
ISS/Atlantis transit of the Sun
21 Sep at 17:03 by Wilson
Thierry Legault, a French photographer, captured a great image of the ISS and Atlantis in front of the Sun as seen from the ground. That was quite an acomplishment, considering that the transit lasted for less than a second.
By the way, I love the picture of his equipment (scroll all the way to the bottom of the page to see it).
Supernova
19 Sep at 16:32 by Wilson
Phil Plait, author of the Bad Astronomy blog, has a great story about an amateur discovering a supernova and how being in a bar can lead to greatness. Worth reading.
Comments OffContinue Reading
NAG
18 Sep at 13:08 by Wilson
I should probably have written about this earlier, but…
I’ve started attending the meetings of the New Astronomers Group of the ASV. The intake meeting was at the end of August, and the first regular meeting I attended was two weeks ago, on the 6th. Meeting happen on the first Wednesday of each month.
The NAG is a semi-formal group of “beginners” with the intention of introducing people to astronomy. Each monthly meeting includes a talk about a specific subject, ranging from astronomy theory to very practical, observation-related issues. The intake meeting had a general introduction amateur astronomy and useful tools (such as a planisphere and a red torch), including an introduction to the society’s 20-inch telescope, and it is intended only for people joining the group (there’s one intake every three months). After joining, you’re part of the group for a year, after which you “graduate” out of it and open space for new people.
Regular meetings seem to be attended by around 20 people (although I’m told attendance can vary wildly depending on the subject to be discussed and the weather); this month’s meeting (which happened on a cold, rainy night) was on the subject of the life-cycle of stars, discussing the birth and death of stars and everything in between (the main sequence, supernovae, red giants, white and brown dwarves etc.). Pretty interesting, even though I knew most of the material and I had to leave a few minutes early due to tram schedules.
It’s a pretty good way of meeting like-minded people and getting to know other members of the society (the meetings are open only to ASV members); people talk about what they’re learning and doing, bring their instruments so that people with more experience can teach them to use them, bring interesting material they find on the net and so on. I hope to learn quite a bit from the group. For those who might want more information about the group, go to the ASV website.
Partial lunar eclipse next week
2 Sep at 12:21 by Wilson
A partial lunar eclipse will be visible in Australia next week. Eastern Australia will see the moon set while still eclipsed (in Earth’s penumbra, but already out of the umbra), while the rest of the country (West Australia, Northern Territory and most of South Australia) will see the full eclipse.
The eclipse (umbra) starts (first contact happens) at 18:05 UTC on the 7th of September, which is 4:05 AEST the next day, peaks at 18:51 UTC (4:51 AEST) and ends at 19:37 UTC (5:37 AEST). The penumbral eclipse extends until 21:00 UTC (7:00 AEST) but the moon will set before that: in Melbourne, it will set at 6:12 (so you won’t miss much of it). If you are a very early riser and have a good view of the western horizon, that will be a great way of starting the day.
Recapitulating, the eclipse starts at 4:05am AEST on 08 September (early next Friday morning). Full details can be seen at the Theodore Lunar Observatory website.
Comments OffContinue Reading
The sky tonight
15 Jun at 16:47 by Wilson
If you are in a location from which you have a reasonably dark sky and a good view to the west, go outside today just after sunset and look up. Saturn and Mars will be very close together somewhat low in the northwest sky, and this should be visible with your naked eyes from almost anywhere. The image you see here (generated with Stellarium) shows their relative positions as they will be around 18:30 tonight, in Melbourne; the view will be similar from other locations at similar local times. From Melbourne, Mars will set at 20:25 and Saturn right after at 20:41.
Also, if you go out a little earlier, Mercury will be making a very good appearance, much closer to the horizon; it will set at 18:41, so you will have to look for it against a sky that will still be a little bright.
The cluster of stars you see behind Mars in the image is the Beehive cluster (NGC 2632), but it will offer a much better view with binoculars than with your naked eyes.
If you can’t go out tonight, don’t despair: the two outer planets will be even closer at the same time tomorrow, but Mars will have almost finished clearing the Beehive by then. If you want to catch Mars on top of the cluster, this is the day.
Comments OffContinue Reading
Choosing binoculars – part 2
13 Jun at 16:49 by Wilson
In part 1, I covered three important variables to watch for when choosing a binocular: magnification, aperture and the size of the exit pupil. Now, I’ll go through a few more.
Coatings
Gathering light is important, but not losing it after it’s gathered is just as important. Every time light crosses from air into glass or vice-versa, not all light actually gets through: some of it is reflected or scattered away. The loss of light can be of up to 5% on each transition, and a binocular may have as many as 16 air-to-glass or glass-to-air transitions inside it. This could cause as much as 55% of the light to be lost before it reaches your eyes. And that’s why lenses and prisms need to be coated.
The function of the coatings is to prevent light from being reflected. High-quality, multi-layer coatings can reduce the reflections to 0.25% of the incoming light, or even less; this will significantly improve the quality and brightness of the image. You want binoculars that are described as “fully multi-coated”, that is, all glass surfaces are coated with multiple layers. “Fully coated” means that all surfaces are coated, but not all (or any) have multiple layers, while “multicoated” means that some surfaces have multiple layers, but some have nothing.
A quick way to check for coatings if you have the binoculars in your hands: look at the reflections from the ceiling lights on the objectives. You should see several faint reflections, but none of them should be white. White reflections indicate the presence of non-coated surfaces somewhere in the optics; avoid instruments with this. Also, avoid “ruby coated” binoculars; the reflect large amounts of light and distort the colour of the light that does get through (the image will look greenish).
Focusing
In short, you need binoculars that allow you to adjust the focus differently for each eye; this can take the form of individual adjustment selectors for each eyepiece or a single central focusing selector with a separate adjustment knob for the right eyepiece. Either of these is acceptable, and mostly a matter of preference (but make sure that you can adjust for eye differences; this is important). Binoculars with individual adjustments for each side tend to be more resistant to water infiltration, but that will depend mostly on the quality of the instrument.
Field of view
This is the amount of sky you can see through your binoculars at a time. For astronomy, the wider, the better, up to a point: if the field of view is too large, you will get distortion near the edges of the image.
The field of view can be expressed in degrees or in “feet at 1,000 yards” (which refers to the width of the image you see). In metric countries, sometimes you also see “meters at 1,000 meters”. You want something in the range of 5 to 10 degrees, which is the same as 260 to 520 feet at 1,000 yards, or 90 to 180 meters at 1,000 meters.
This measure is strongly related to magnification; the larger the magnification, the smaller the field of view.
If you wear eyeglasses
Some binocular features are interesting for people with eyeglasses; one of them is called “long eye relief”. Eye relief is the distance from the eyepieces at which the image is in focus; that is, it tells you how far away you can be from the binocular while still being able to see the image. For eyeglass wearers who intend to use the binoculars without taking their glasses off, this needs to be long, in the vicinity of 20mm.
Also, ensure that the instrument has retractable or fold-down eye cups, so that you can get the eyeglasses close to the eyepiece without the cups getting in the way.
That said, I personally prefer to take the glasses off and use the binocular with the eye cups up. It is more comfortable for me, and it makes it easier to keep the image forming in the right place (with the glasses on I found it too easy to move my pupils out of the image). Unless you are very near- of far-sighted, you will see everything in focus with or without glasses.
Conclusion
To sum things up, you will want binoculars with:
- magnification not lower than 8x and not much higher than 10x (and definitely not higher than 12x if you don’t want to use tripods)
- aperture not smaller than 40mm and not much larger than 50mm
- exit pupil between 5 and 7mm
- fully multi-coated optics
- independent focus adjustment (either one control per eyepiece, or a central one with an extra adjustment for the right pupil)
- field of view of 5 to 10 degrees
- and, if you wear eyeglasses, long eye relief and retractable eye cups
And, finally, you want to test the binoculars before you buy them. Hold it in your hands, make sure that it is solidly built, make sure that it is not too heavy to hold for long periods of time and so on. Repeat this with several models, see how they feel in your hands, see if you can perceive differences in the images. Prices can vary a lot; try to test both cheap and expensive models. Give preference to stores that cater to amateur astronomers instead of retail camera or general stores (that is, do not buy binoculars from Walmart unless you know what you’re doing). Also, read this page and do everything it tells you to. Good luck, and clear skies!
(for the record, I bought an 11×56 binocular from Aquila Optical, in Sydney, and I’m quite satisfied with it)
RECENT COMMENTS