A Universal Name Resolver

I hope you've been following my last two posts, about astronomical imagery metadata and microformats, as they set the stage for this one. I got to the point of playing about with the implementation of an unofficial microformat for the official Astronomy Visualisation Metadata standard under development. Shortly after I started playing I realised that not many people would have the patience to sit and fill in fields detailing the object name, the coordinates, the type of object etc etc. The AVM folks have made a nice online tool to help, but really it should be possible to complete a lot of those fields automatically given the object name.

To make a tool to automagically generate my proposed microformat I have, almost accidentally, created a Universal Name Resolver; something that can provide the properties of an object given a common (or even uncommon) name for it. Want to know the RA/Dec of the Crab Nebula, C2, Mercury, SN 2008D, or Apophis? Perhaps you want to know what OGLE-TR-56 b and M87 are?

These types of services existed already but the trouble was that they have grown up from different areas of astronomy and space science and no single one covers the entire universe, as far as I'm aware. You can use the SkyBot name resolver within the Solar System (except for comets), NED to lookup extragalactic objects, and SIMBAD to find most astronomical objects inbetween. Those three don't include many supernovae and recent extrasolar planet discoveries but that is easily solved by looking in the Extrasolar Planet Encyclopedia and the Central Bureau of Astronomical Telegrams Supernova list.

What I have done is create some software (with the benefit of the excellent WCSTools package) which talks to each service until it can find the object specified. It also compares against the supernovae, extrasolar planet, constellation, and Caldwell catalogues and works out the full AVM taxonomy listing for objects whilst it is at it. This is really a case of building on the shoulders of giants as the really hard job of parsing through hundreds of astronomical catalogues is done by the wonderful SkyBot, SIMBAD, and NED services.

As with my proposed microformat, this really is a work in progress and is certainly not perfect. Even if it doesn't get used for microformats, I could see it being pretty useful in its own right. Please let me have feedback about it in the comments. Before I finish, thanks to my early testers Dave P and Tom for their suggestions and comments. Dave even went as far as to make an EMACS script which calls it!

Posted in astro blog by Stuart on Wednesday 27th Aug 2008 (16:00 BST) | Permalink

Astronomy Metadata and Microformats

As I described in my last post, the efforts to tag astronomical images with useful information is well under way. However, the current plans are only to tag images. That ignores the huge amounts of astronomical content delivered asvideo, audio or prose. Suppose you wanted to find episodes of your favourite podcasts that contained a particular type of astronomicalobject, video clips of the Andromeda Galaxy, or blog posts describingobjects near to 05:34:32 +22:00:52. None of those would be tagged as they aren't static images.

What can be done to tag these other types of data? It may be possible to adapt ID3 tags in MP3s - usually used to store the artist, the track name etc - to include some of the AVM standard (PDF). Some of the image metadata is not appropriate for audio but some extra metadata (e.g. start time and stop time within the track) would also be required. It should be possible to add tags to videos in similar ways and that will also call for some video specific tagging. One issue may be the huge file sizes of audio and video. Luckily, I think most metadata tag information, in modern media files, is stored at the start of the file (it is for ID3v2 tags) so it isn't necessary to download the entire file to catalogue it. I still think that to start transferring these huge media files seems slightly inefficient and this is where I think a more lightweight approach could be useful. So, I suggest that we create an AVM microformat.

Microformats are a way to use existing code such as HTML and CSS (also known as POSH to people who like making up new acronyms) to add metadata to webpages. Microformats are great because they can be applied to existing webpages without changing how they look and feel but allow computers to extract the metadata. One example of a microformat in the wild is the vCard (or hCard). This is a microformat to describe people, companies and organisations. This is already used on sites such as Twitter to mark up the little icons of people who are followed by users.

Grabbing data from microformats is quite straightforward too. SixApart has details of an hCard Perl library for parsing hCards from webpages and this type of thing could be adapted. I have created a page with my proposal for an AVM microformat (implementing tags which were not image specific) and it would be great to have feedback. Perhaps you have suggestions for improvements, perhaps you think it is a total waste of my time and effort. Please post your responses in the comments to this post.

Posted in astro blog by Stuart on Wednesday 27th Aug 2008 (15:06 BST) | Permalink

Describing Pretty Pictures

If you've ever wanted to find images of Venus you might have used a search engine such as Google. The results can be variable and can often throw up the planet, the goddess, the Venus di Milo and even models of mobile phone. The trouble is that search engines are trying their best to work out what an image is from the surrounding text on the webpage but that doesn't always help distinguish different things with the same name. We really need a way to say that a particular image is of the planet Venus and not a brand of lady's razor. For this we need metadata; some extra data describing what the main data are.

The basic idea is to label your data - images, videos, audio or even text - in a standard way so that computers can have a good idea as to what it is. In professional astronomy this has been done for years using the Flexible Image Transport System (FITS) for image data. FITS files can contain all sorts of information including the object, the coordinates, the observing wavelength and much, much more. Having that information with the image can be a life saver if you lose your log book or forget what an image is of. The downside of FITS is that it has never really taken off outside the professional astronomical community despite projects such as FITS Liberator from ESA/Hubble. Trying to get everyone to adopt FITS when JPEG, BMP, GIF, PNG are so widespread really isn't going to happen. So, what do you do? You try to adapt the common file formats we have already to include the metadata.

One of the key projects for the International Year of Astronomy is the Virtual Astronomy Multimedia Project (VAMP). Their aim is to get creators of pretty pictures - astronomical imagery used foreducation and public outreach (EPO) - to tag them with as much information as is relevant. The aim is to allow the creation of easily searchable databases of astronomical imagery for a range of potential applications. The VAMP project will use methods similar to the way digital cameras already tag images with basic information such as the camera model. The project has been working since last year and the final candidate document for the VAMP standard (AVM) has been out for a few months. They even have a prototype online tagging tool, which will generate an XML file which can be attached to your image in Photoshop or Adobe Bridge, so they are in good shape.

While I think the VAMP project still has some more work to do, these efforts will soon make it easy for everyone to tag their astronomical pictures. I look forward to the day I can use Google to search the web for beautiful images by right ascension/declination, observing wavelength or even by type of astronomical object.

Tags: | | |
Posted in astro blog by Stuart on Tuesday 26th Aug 2008 (20:44 BST) | Permalink

Don't Look At The Sun - part 2

Eclipses and transits of the Sun are amazing celestial events. They can be awe-inspiring and beautiful and enthuse people to travel the world to experience them. At the same time they can be dangerous. The Sun is a ball of gas about 330,000 times more massive than the Earth with a core undergoing nuclear fusion reactions. As a result, and given that we are only 149 million kilometres from it, the Sun is very bright. Astronomers always warn that these events should be viewed with safe solar viewing equipment so that you don't damage your eyes.

Back in 2004, in the weeks leading up to the transit of Venus, Megan and I filmed the result of focussing light from a small telescope onto a grape. Whilst far from a perfect analogy for the human eye, the sound of sizzling grape and the burnt patch on it were enough to remind me of why it is a bad idea! Yesterday, I received a comment on that post from Matthew who had been told about the "benefits of looking directly at the morning (rising) sun". He asked me if it was good to look at the Sun. The simple answer is no.

Human eyes are extremely sensitive optical instruments that can deal with a huge range of conditions. Some have even been known to detect just a few photons of light in the dark. That is a very impressive level of sensitivity. However, increasing the light levels considerably above ambient amounts starts to cause damage.

One of the classic things for a child with a magnifying glass to do is to burn an ant (in the interests of ant safety I don't recommend this). The ant burns because the sunlight is focussed from a large area (that of the magnifying glass) down into a small point making the light more intense. By staring directly at the Sun you are effectively using your eye's lens as the magnifying glass and your retina as the ant. However, it isn't just the increase in temperature that causes damage to your eyes. For a start you'll be getting more UV and infra-red radiation into your eyes. Secondly, the very intense visible light - safe solar filters reduce the luminosity by more than 33,000 times - starts a series of complex chemical reactions which will stop the cells responding to visual stimulus and can destroy them. Killing off cells in your retina is not a good thing. What makes this more scary is that there are no pain receptors in your retina so you can't even feel the damage being done.

Matthew pointed me to a website that made me pretty concerned. The website is about Sunyogi Umasankar who, apparently, stares at the Sun for extended periods. I do not recommend this and am very sceptical about some of the claims. Interestingly, some of the initial visual effects described on that site sound fairly realistic for someone causing damage to their eyes. One claim, that the Sun started to appear as a "clear hazy ring with soft blue sky inside", sounds similar to an after image of staring at a red light and then at a white surface. The Sun, especially at sunrise and sunset, usually appears at the redder end of the spectrum because the long path of the light through the atmosphere tends to scatter out the blue light. I can imagine that staring at a red light source for extended times will de-sensitise the cells to red light whilst neighbouring cells (those seeing the blue sky) won't. The brain may very well interpret the information from the cells seeing the Sun as the complementary colour. However, I don't want to try this experiment myself. Another site describes a Japanese man's account of staring at the Sun. He says he saw 'auras' around family members after staring at the Sun. It's hard not to think of these as a combination of after images and possible long-term damage to his eyes.

Ultimately, you can choose what to do with your own eyes. There is no evidence that it benefits your health and indeed it is very likely to cause long-term damage to your vision. You can damage your vision if you want to but I prefer to enjoy the beautiful colours and sights of the universe around me with a pair of nice, healthy eyes.

Tags: | |
Posted in astro blog by Stuart on Friday 22nd Aug 2008 (19:51 BST) | Permalink

It's quiet around here

I haven't posted here in nearly two weeks. That is perhaps the longest gap I've ever had between posts since I started back in 2003. There are several reasons mostly to do with being quite tired and needing a break from it all. In that time I have been tweeting as that requires very little effort and mean that I don't have to write a full blog entry. The only times I've had anything to blog about (such as the great partial solar eclipse) I've been too busy or away from a computer. Anyway, some real blog posts will be appearing here shortly.

Before I go, remember that the peak of the 2008 Perseid meteor shower (not Comet Perseid as the Littlehampton Gazette thinks) is around now. If it is dark and clear where you are, prepare yourself then get outside and have a look for shooting stars (meteors). The zenith hourly rate seems to be up at around 70 or so so you should see around one per minute.

Tags: |
Posted in astro blog by Stuart on Tuesday 12th Aug 2008 (20:10 BST) | Permalink
[an error occurred while processing this directive]