Finding Astronomy Data on the Internet

<body bgcolor=444444 text=ffffff link=ffff00 vlink=007700> <h1>Data on the Internet</h1> If you are seeing this document, then your web browser can't handle frames, so this may be a bit cumbersome, but not too bad. <h1> Step1: Pick an object.</h1> Here is a list of objects that are suitable for this assignment. Pick one and write down its NGC number, so you can enter it in each page's search form. Some of the objects have other kinds of names. <strong>The NGC number is the best name to use</strong>, if it is available. (NGC stands for New General Catalogue, the most widely used catalog of celestial objects). <ul> <li> Hubble Deep Field <li> a gaseous nebula: The Eagle Nebula , M16, NGC 6611 <li> a spiral galaxy: M51, NGC 5194 <li> an Elliptical Galaxy: M87, NGC 4486 <li> an Irregular Galaxy: M82, NGC 3034 <li> a Globular Cluster: M3, NGC 5272 <li> an OB association: 30 Doradus, NGC 2070 <li> a supernova remnant: M1, NGC 1952 </ul> <hr> Click on <a href="http://stdatu.stsci.edu/dss/">DSS</a> to go to the Digitized Sky Survey when you have chosen an object. <h1>Step 2: Getting a Photograph of your Object</h1> Once you are at the DSS page, you will see a web form with many fill-out fields. The first one is labelled <strong>Object name</strong>. Type in the <code>NGC</code> name in this field (e.g., <code>ngc 3379</code>). Then click on <strong>GET COORDINATES</strong>. After it looks up the coordinates of your object, the page will reload, with your coordinates in the <strong>RA</strong> and <strong>Dec</strong> fill-out fields (you may have to scroll down a bit to see them). <p> Next, scroll down to the form field labelled <strong>file format</strong> and choose <code>GIF</code>. You can leave the rest of the form alone. <p> Click on <strong>RETRIEVE IMAGE</strong>. In a few seconds, your image will appear. Pretty, isn't it? <h1>Step 3: Images from other Wavelengths</h1> As we learned in class, visible light is only a small part of the EM spectrum. The next document we will explore is really cool. It is the home page for the <a href="http://">SkyView</a> All-Sky Viewer. It contains images from every part of the sky in many different wavelengths: radio, infrared, visible, ultraviolet, X-ray, and Gamma-ray! <p> The format of the page is similar to the DSS page. Click on <a href="http://">SkyView</a> at any time to go to the All-Sky Viewer page. <p> Once you are there, just type the name of your object (<code>NGC nnnn</code> is best) where it says <strong>coordinates or source</strong>, and select all of the six wavelength regimes from the table below. Scroll down below the wavelength table, to the selection box labelled <strong>image size (degrees)</strong>. Select <code>3.00</code> from the list. Finally, scroll back to the top and click on <strong>Submit</strong>. <p> A little while later (it takes a bit to process your request), six images will appear. They might look very different, but each is of the same object viewed in a different kind of EM radiation. Why do you think they look so different? (One thing to keep in mind is that the size of the images is not the same in each case. The optical image is 7.5 degrees on each side; the gamma ray and X ray images are 150 degrees on the sky -- nearly half of the entire sky!) <p> We will end this lesson with the <em>Big Tamale</em> of astronomy, the Hubble Space Telescope! <h1>Step 4: Getting an HST Image of your Object</h1> You know the drill by now: Type the name of your object <code>(NGC **** is best)</code> where it says <strong>Target Name</strong>, then press <strong>Resolve</strong>. We are interested in pictures rather than spectra, so de-select the options under <strong>Spectra</strong>. Everything else can be left blank. Click on <strong>Search</strong>. <p> A little while later, it will give you a big table of all the images of your object it found in the HST archive. There will probably be very many images, but lots of them are calibration images. Look under <strong>Target Name</strong> to see which images are actually interesting. For example, if you are doing M1, then look for "crab nebula" or "pulsar". Also, look under <strong>Instrument</strong> for WFPC2. These are the best pictures. <p> This archive exists for professional astronomers to download Hubble data, but you have to be registered with NASA to do this. We can <em>preview</em> the images, however. Click on the <strong>Target Name</strong> of the object youwish to preview. A new window comes up. Click on <strong>Get Preview</strong>, and the image will load. <p> Warning: Sometimes these images are empty, or bad quality. If this happens, try one of the other images. Especially try different wavelengths. You should be able to find a good image. <p> Note especially the improved quality of the HST image over the DSS image. If you got a WFPC2 image, draw the outline of the image. Why do you think it has that funny shape? HST is not a large telescope. It is smaller than the one that took the DSS images. Why are the Hubble images so much better, then? <hr> <address>jharris@ucolick.org</address>  Last modified: Mon Apr 7 15:24:19 1997  </body> </html> <hr> <address>jharris@ucolick.org</address>  Last modified: Mon Apr 7 15:23:44 1997  </body> </html> <hr> <address>jharris@ucolick.org</address>  Last modified: Mon Mar 2 00:09:21 1998  </body>