Wednesday, April 30, 2008
My first astronomical sketches were of the Moon, done through my Dad’s binoculars resting on my window sill. I’ve been sketching stars, planets and comets for years using a 115 mm reflector with no tracking. Almost anyone with an entry level telescope can sketch the Moon, Jupiter, Saturn, the later crescent phases of Venus and Mars at opposition. I even have sketched the sky as seen by my unaided eye to record movements of comets and planets.
On the other hand, making sketches does require some minimal form of manual dexterity. Still, sketching planets and stars is an entirely different proposition to drawing the Mona Lisa, so if you can set up a telescope without tangling yourself in cables, you should be able to produce a satisfying and workable sketch.
As with anything astronomical, a little preparation repays dividends at the telescope. Most people keep observing logs; it is very simple to combine an observing log with a sketch book. I use semi cartridge 110 gsm acid free drawing paper, A5 size in a spiral bound notebook. For me this is the right size for portability and ease of holding at the telescope. This sort of drawing paper can be found at all good newsagents or stationary stores.
At the head of each page I write in headings for the date, time, observing condition (cloudiness, sky quality, wind conditions), and then I draw in observing blanks. These are simple circles where I will draw the image. This is a highly technical production; I use a 2B pencil and the eyepiece dust cap of my telescope to draw a number of circles. I find this just about the right size for reproducing what I see in the scope. More technically minded people can use a popular word processing program to make the blanks, but you really need a laser printer for printing the blanks. Inkjet print will smear when you handle it while sketching, and any trace of dew will wreak havoc. Also, if you are printing out pages, you will need a clipboard or solid surface to support your sheet while sketching.
Having set up your sketching blanks, its worthwhile making sure you have two sharpened 2B pencils with you (or coloured pencils). If a pencil point breaks during sketching you don’t have to hunt around for a sharpener then.
Now you are at the telescope, how are you going to actually sketch? After all, it is dark! I usually do my planetary observing in suburban locations where there is enough stray light to see the page (but not enough to degrade the planetary image), but if you are observing in dark sky sites, I find a hands-free LED headtorch, with red cellophane wrapped around it so your (and other peoples) night vision will not be affected, is ideal. It also helps with all the telescope set up that you do as well. LED head torches can be found relatively cheaply at bushwalking or sports stores, and red cellophane can be found at any newsagent. David Reidy and Ken Wallace recommend one of those booklights that you can clip to a book or clipboard. Experiment a little to find the best and most comfortable method for yourself.
Now, you are at the eyepiece, pencil in hand poised above your planet blank, how do you actually start? I take a good look at the planet, memorize what I have seen, then glance down at the blank and quickly sketch in the major detail. As I wear half glasses for reading, I can wear the glasses at the telescope, look through the lens sans glasses, then look through the glasses at the sketch pad. I then look back through the scope, then back to the pad and sketch in more detail. I repeat this until I have built up a detailed sketch of the planet. You may find that the first time you look through the eyepiece, there is little detail, but don’t worry, just sketch out the main features and you will find that as your eye becomes adapted, you will be able to see more detail. Unguided scopes can be a bit of a pain, as you have to bring objects back into the eyepiece fairly often, but I spent most of my sketching career with unguided scopes, and you can still get good sketches. Made a mistake? Don’t panic, just start again, or use an eraser, to clear out the mistake.
It’s worthwhile practicing a bit before trying your hand at planets. The Moon of course is ideal for practise, bright, full of detail, and you can start sketching in the early evening (planets like Jupiter, Saturn and Mars are best when highest in the sky, which is often inconveniently late). Once you have had a go at the Moon, planets should be a doddle. Try experimenting with coloured pencils,. Jupiter, and Mars at opposition, is particularly good for colour. Getting the shade right may be a problem (especially under redlight conditions). Again, don’t be afraid to experiment.
Again, you are not limited to the telescope. I have sketched through binoculars (good for asteroids and moderately bright comets, see the sketch of comet V1 NEAT sketch through binoculars to the left. I made multiple sketches over several days showing the motion of this comet), and with the unaided eye (bright comets, planetary motion etc.), you are limited only by your imagination, a comfy chair and a good supply of sharp pencils. So pick up those pencils and get sketching!
Tuesday, April 29, 2008
Occultation of Neptune by the Moon April 30.
Monday, April 28, 2008
Images from an Occultation
So, after I put him back to bed I was able to rush outside. set up the scope ... and just miss Antares coming out from behind the Moon. *sighs expressively*
Anyway, here are some shots of Antares drawing away from the dark side of the Moon. Enjoy.
Friday, April 25, 2008
9:00 pm April 24, 2008
Carnival of Space #51 is here.
Labels: carnival of space
Thursday, April 24, 2008
Lights! Drama! Action! (and RW Taurii)
Anyway, the Google Video is below, you can use the image to the right to help identify things (click to enlarge), but it is pretty cheesy. You can download a 1.4 Mb Avi, a 4.5 Mb Avi or a 3.5 Mb gif file which will have more detail. It is better to run the AVI's on a loop a 2x magnification to really get a good handle on the various blobs.
Wednesday, April 23, 2008
More Fun with Phase Folding
But the field was fantastic, in the stack, you can watch the California Nebula, see Comets Holmes and Wiratannen move across the field, see several asteroids including Ceres and Amphrite, as well as watching RW Taurii blink on and off. Rather nice indeed.
Tuesday, April 22, 2008
Occultation of Antares 24 April
On the East coast of Australia Antares disappears between roughly 2:45 am and 3 am , and reappears around 4am. In central Australia south of Alice Springs, it disappears around 2 am and reappaears around 3:15 am. in WA it disappears around 11:30 pm on the 23rd, and reappears just before 1:00 am. A full table of contacts for major Australian cities is here.
A table with more details of this occultation, with contact times for other cities (mostly New Zealand) in UT time are here.
Sunday, April 20, 2008
Fun with Phase Folding
There's still a few issues. Even for a bright star like Algol, it's measured intensity is quite different between satellite runs, and I have no clear idea of how to normalize this. Also, the more runs you can fold in, the better your sensitivity. However, 83 Leonis has a long period of 17 days, and you only get two passes in STEREO per year. Still, I'll have another go with Phase folding and see what I can come up with.
Friday, April 18, 2008
Is this a tranisting exoplanet?
This is an intensity trace of 83 Leonis (HD190360 click image to enlarge) assembled by stellar photometry from STEREO images, taken over the time of a predicted transit (17-18 August 2007). 83 Leonis is known to harbour a transiting Saturn-sized exoplanet (well, sort of, no one has actually seen a transit yet, but it is predicted to transit). It is a good STEREO candidate as it is fairly bright (magnitude 6.5) almost slap bang in the middle of the Secchi H1 field (where there is less distortion) and it has a fairly deep transit (which should rise above the inevitable noise).
So, the trace shows what appears to be an observable dip in intensity. The dip in intensity is roughly the right depth (1% vs predicted 1.95), the minimum is close to the predicted minimum, but the dip is a little too broad (the transit should be 4 hours wide, this is more like 6).
And it is noisy, especially the early measurements, during the 17th. The noise suggests this is all artefact.
Of course, I've compared the trace from 83 Leonis with nearby stars of similar magnitude (80 Leonis, A2777 etc.), and they are also, ahem, noisy. One thing they all seemed to have in common (apart from a bucket load of noise), is they all seemed to be going up in intensity when 83 Leonis was going down and down when 83 Leonis was going up. So I averaged the values from the 4 stars closest in brightness to 83 Leonis (the dimmer stars were more variable), and compared the average to the 83 Leonis trace.
I should explain that to make these figures I have taken the raw intensities, subtracted the background, then expressed them as a percent of the average of the last six raw intensity values (you can use the last value, or the average of all values, the pattern is the same). You can't effectively compare the raw traces as they differ substantially in intensity (for 3000 to 9000 arbitrary intensity units). Expressing everything as a percentage change in intensity makes them comparable.
Now the values can drift because of differences in pixel sensitivity, effects of coronal mass ejections, systematic differences in the regions of the chip and just plain randomness. If the changes in intensity in the stars on the chip of the H1 imager are random, then averaging them out should cause the values to regress to the mean. If there is systematic error, this should be picked up by averaging too. The stars I've picked are all close by 83 Leonis (within about 1 degree), so the local conditions should be pretty similar.
Anyway, what you can see is that the other stars do behave differently to 83 Leonis. If there was some systematic effect, 83 leonis's trace should follow the averaged traces. More importantly, the "dip" in the 83 Leonis trace is outside of the error bars for the other stars, suggesting that the dip in the trace for 83 Leonis is bigger than what one could expect from random variation.
So maybe, just maybe, this might be a real exoplanet detection. Or maybe I'm just chasing errors. After all, what I know about astrophotometery could be written on a postage stamp. So if anyone has good ideas for generating pseudo flat fields and darkframes from the STEREO images that a mathematically challenged biologist can understand, drop me a line.
Now I'm going to take a break. It's taken me a month to assemble the images, find freaking 83 Leonis (a post about that later) and do the photometery and analysis. Plus my sister-in-law and family are visiting. Catch you later.
I gratefully acknowledge the assistance and helpful discussion from Professor Glenn White of the Open University, Professor Greg Laughlin and Comet Al. Without these folks I wouldn't have known where to look or how to begin analyse my data.
Carnival of Space #50 is here.
Labels: carnival of space
Thursday, April 17, 2008
Comet 17P Holmes and the California Nebula in Stereo
I've posted an animation below, 29 Amphrite is also in the frame, but it's hard to see in the Google Video, you are going to have to download the avi (1.1 Mb) from here, and then run it at 2x magnification to see this asteroid easily. Just below Amphrite is what appears to be another asteroid, but nothing appears on my star maps. An artefact or a real unknown object? (update: Comet Al has identified this as 46P/ Wirtanen) 1 Ceres was also clearly visible, but is outside the area of this animation.
In making these images I've just updated ImageJ to version 1.39u, and it rocks! Finally got the Z profiler to work, and the Astrometry program is sort of working, so I will have another go at exoplanets real soon.
Wednesday, April 16, 2008
So much irony, so little time.
By your logic, it was right for Galileo to be persecuted for his views, because the overwhelming majority of astronomers were certain that geocentrism was right and heliocentrism was wrong. The evidence was just so overwhelmingly obvious. The same goes for virtually any other scientist that revolutionized his discipline.
Can't these people get their history right? If you would have polled astronomers in 1610, after the publication of Sidereus Nuncius (The Starry Messenger) and well before Galileo fronted the inquisition or was persecuted, you would have found that most astronomers would regard the Copernican heliocentric model as computationally convenient. It made predicting planetary positions easier, having got rid of many (but not all) of the epicycles that bedeviled the Ptolemaic geocentric theory (for a series of Java animations that illustrate geocentric theory, see here). It also provided a natural explanation for retrograde planetary motion. On the other hand, stellar parallax had not been observed, and with the Copernican system there was no obvious replacement for the system of Aristotelian physics that, for example, produced gravity, so its status as an explanatory theory was not firm. However, Galileo's observations of the Medician Stars and his work on physics significantly dented Aristotelian physics, making the Aristotelian argument against Copernicanism less compelling and throwing open the geocentric question again. This was a time of great ferment in astronomy as astronomers made their own telescopes and confirmed Galileo's observations while making new observations of their own.
One thing we can definitively say about this time was that there was no consensus amongst astronomers, in the sense of our modern consensuses about relativity, quantum mechanics, evolutionary theory or global warming. In
Then Galileo discovered the Phases of Venus, and the Ptolemaic geocentric system was effectively dead from then on. There was no way the phases of Venus could be compatible with a Ptolemaic geocentric system. By the time Galileo first fronted the inquisition in 1616, the Ptolemaic geocentric system was consigned to the trash heap by almost every astronomer. The big battle was between the Tychonian geocentric system, where all the planets except Earth orbited the Sun, and the Sun orbited the Earth. This system was mathematically equivalent to the Copernican system, but was obviously a kludge, and furthermore, broke Aristotelian physics. It was definitely not “overwhelmingly obvious” that the Tychonian system was supported over the Copernican system.
Where were the astronomers when Galileo fronted the inquisition for the first time? Right behind him. The Academy of the Lynxes, the Italian equivalent of the American Association for the Advancement of Science, or the
It took some time to provide a definitive observation of the Earths rotation, and longer still to demonstrate stellar parallax, but by the time of Galileo’s trial there was unequivocally no consensus that geocentrism was right, with no overwhelming evidence supporting geocentrism. Indeed, it could well be argued that by the time of Galileo’s trial, and during most of Galileo’s time of persecution (if you take 1616 as the start of his persecution, rather than the beginnings of the call to be tried for heresy) the balance was well and truly tipped in favour of heliocentrism in Europe overall.
Ironically, it wasn’t astronomers who were persecuting Galileo (even though he did have some very vigorous arguments with some astronomers), it was the Church. A point Ken seems to have forgotten.Then again, history is beside the point really. No one, least of all Wesley Elsberry, is claiming people should be persecuted for not accepting the consensus. Heck, in science people reject the consensus all the time (look at Fred Hoyle for example). But if you reject the consensus, there is no obligation of anyone to listen to you unless you bring data to the argument. Galileo bought lots of data, he had reams of falsifiable observations and experiments. He deeply engaged with the scientific community of his time, with extensive correspondence on things such as construction of telescopes (so people could check his claims). His work inspired scientists of that age, and lead to much fruitful research, essentially establishing modern science.
In contrast, the Intelligent Design people actively shun engagement with the scientific community, have produced no data, just arguments from ignorance and waving lots of big numbers in the air (see also here, here, here and here). Yet they moan and carry on when scientists ignore them. Sorry folks, being ignored is not persecution. You can't even get to the first part of "It is not enough to be persecuted to wear the mantle of Galileo, you also have to be right".
Ironically, while Galileo was being persecuted, he produced Discourses and Mathematical Demonstrations Relating to Two New Sciences, possibly the foundational document of modern physics. In contrast, the intelligent design movement has come up with a couple of pop-culture, data free books (see here). Galileo? I don't think so.
*What is it with these people, ID supporters turn out to be global warming deniers and HIV deniers as well. Is there no pseudoscience they don't like?
Labels: Intelligent design
Tuesday, April 15, 2008
Viewing the Moon, Saturn and Regulus
Laser elevators OR xkcd has a blog
Rummaging around on the intertubes, I found that the canonical geek web comic, xkcd, has a blog (or blag as he calls it). Now, I find xkcd to be side splittingly funny (and insightful), but it’s not to everyone’s taste. Nonetheless, I think you might find this discussion of laser elevators relevant to my previous laser pointer post . A laser elevator is where you use laser to lift an object into orbit (or power a star sail).
Monday, April 14, 2008
The Moon, Saturn and Regulus, April 15
Another close approach of the Moon to Regulus and Saturn. Should look quite nice too. Mars forms a triangle with Castor and Pollux, as an added bonus.
Friday, April 11, 2008
Phobos in 3D
Quick, grab some red/blue 3D glasses and lok at this image of the Martian moon Phobos. Then go "Wow" like I did. The image really pops out at you.
For more info, a bigger and even more stunning 3D image and some more detailed images, pop over to the Mars Reconnaissance Orbiter site, and have a look at their stories on Phobos and Phobos in stereo.
Also have a look at Tom's take on the story.
Carnival of Space #49 is here.
Labels: carnival of space
Thursday, April 10, 2008
Labels: sky phenomena
Wednesday, April 09, 2008
Let a Million Laserpointers Bloom
An aide runs into the office of the US president and pants "Mr. President, the Russians are painting the Moon red!". The president just nods and keeps on working. A little while later the aide runs in again "Mr. President, the Russians have painted half the Moon red!" The president just nods and keeps on working. Finally the aide runs in "Mr. President! The Russians have painted the entire Moon red!" The president looks up and says "Now get those NASA boys on the phone and get then to take up some white Paint and write "Cocoa-Cola" up there."
This joke came back to me as I was watching a news item about the local Adelaide idiot who was arrested and sent to jail for nearly three years for shining laser light into a helicopter pilots eyes. This comes on top of a series of laser pointer attacks on aircraft coming in to land at Sydney airport. Uh, why you ask, does this remind me of that joke, there is nothing remotely funny about this? What is the connection? Now, my mind runs in all sorts of tangents, but there is a connection.
The connection is the idea that you could try and paint the Moon with laser pointers. Of course, it turns out to be impractical, as almost every person on Earth would need around aim 100 million laser pointers at the full Moon to colour it. This in turn bought to mind the US beer company Rolling Rock's "Moonvertising". Yes, I know it can't work as they state it (come on, it's a PR stunt for a beer company for goodness sakes! They can't even get their diagram of the Moon right, so even if they had a ginormous laser, they couldn't aim to write anything, and yes, I know the Bad Astronomer has already blogged this, but let me have my moment in laser illumination).
Now, the idea of advertising using space objects isn't new, it has been used by Arthur C Clarke in "Watch This Space" and Issac Asimov's "Buy Jupiter", and there has been the odd April fools joke before, and an Advertise on the Moon site (could be a hoax that one). Is it feasible?
Yes, for a suitably expensive definition of "feasible". The Rolling Rock, Advertise on the Moon and Laser Pointer scenarios all use the full Moon for a target. The full Moon has a number of advantages. It's visible all night, it is uniformly illuminated, so you could use the whole face of the Moon without contrast breaking things up.
On the downside, the illuminated Moon is bright, your laser has to overcome the light already reflected by the Moon. Also the Moon is SMALL, around 0.5 degrees wide, you can cover it's image with your thumb. So you are not going to be able to get any sophisticated image or text up there.
(Darlek Laser image copyright Peter Ward)
Under the "Paint the Moon" scenario you need to cover the entire Moon surface, and Julian calculated (under simplifying assumptions) that you would need 6.6 × 1017 watts to do the trick (That is nearly an exawatt). The most powerful laser available is 500 Terawatts formed from combining 192 laser beams. This is about 100 times too weak to do the job, even if all the laser beams weren't plugged into an experimental fusion reactor.
But for an ad we don't need to paint the entire Moon. We just need to illuminate a smaller spot. To illuminate a single dot on the Moon that is visible from Earth is a lot easier. Especially if we aim our laser at the unilluminated part of a crescent Moon. Patricia Daukantas at the Optics and Photonics News Blog calculated that you would need (depending on your assumptions) between a 1 to 100 Giggawatt laser to produce a visible dot on the unilluminated part of a crescent Moon. This is a lot more feasible than a Terawatt laser, and there are a few gigawatt lasers lying around. They just produce these levels for less than a picosecond (that's really, really short).
If we want to make an advertising message on the Moon, we need to drive that spot along the surface, to form a raster image like on a television screen. So the dot has to last a lot longer than a picosecond. You could get around this by firing a lot of gigawatt lasers in sequence, but as need around 2.5% of the total US energy consumption to power one of these lasers, you are looking at quite an energy bill.
So the answer to "is it feasible" is "yes, sort of", if you are willing to hijack a whole bunch (possibly the entire Earth's supply) of major experimental lasers and have the GDP of a small European nation in disposable cash to pay for the power, for an add that can only be seen on a handful of days when the Lunar crescent is sufficiently small to not interfere with the visiblity of the dot on the dark side, for a few hours before the crescent Moon sets. (new Moon and one day old Moon's won't work as they too near the Sun, and the spot will be lost in the sky brightness). Good luck with that.
Of course, seeing as the "missile killer" lasers are only around the megawatt range, the local aviation authorities might object to firing gigawatt lasers anywhere near flight paths (and the Birdwatchers probably wouldn't be too happy with all the fried wildfowl generated). Still, they are minor difficulties compared to what you will have to go through to get the lasers. It had better be a good logo.
Anyway, as you are reading this, lasers are bouncing off the Moon. They are bouncing off the mirror cubes (disco is good for something) left behind by the Apollo astronauts. Of course, you need a 3.5 meter telescope and really good photomultiplier's to detect these laser beams, and no one is making beer adds with them, but it is nice to know that they are there.
Great Old Maps
Monday, April 07, 2008
Crescent Moon and Pleiades, Wednesday April 9
On the early evening of Wednesday, April 9, The crescent Moon will be not far from the delightful Pleiades cluster. This will be best observed around an hour after sunset, when the sky is dark enough to see the Pleiades properly. However, they will be fairly close to the western horizon, so choose a clear, level spot to observe from.
Sunday, April 06, 2008
Venus and Mercury Together
Venus and mercury close together on the morning of 26 March, taken from my Mum's place. Mum has the radio alarm go on at 5:30 am, so it's easy to wale up. So must the rest of the neighbourhood, I could hear the radio from the street as I took this picture.
Saturday, April 05, 2008
Viewing the Moon, Mercury and Venus
I staggered out into the morning, and after a moment I realised that the sky wasn't covered with cloud, as it has been for the past few days. S0 I dug out my camera and headed out into the street to catch the planets.
While the sky wasn't covered in cloud, there was an inconvenient patch just where the Moon and Venus was. Fortunately, the cloud moved away and I was able to catch the three before the sky became too light. Then it was off to wake Eldest One to go to his cricket match.
Where is Mercury, you ask?Look carefully at the image (you may need to click on it to enlarge it) and you will see Mercury peaking out from behind the chimney on the lower right. It's easier to see in the animation below.
Carnival of Space #48 is here.
Oh, and Carnival of Space will be one year old next week. Keep a look out for extra special posts then.
Labels: carnival of space
Friday, April 04, 2008
And a big hole is found in Western Australia
Tuesday, April 01, 2008
The Moon, Venus and Mercury, April 5.
The trio will be reasonably close to the horizon, so it is best if you have a clear, level eastern horizon.