Using SDSS Navigator

Let's look at the properties of Abell 2065. The cluster's sky position is

(RA,Dec) = (230.62156, +27.70763)

where both coordinates are given in decimal degrees.

Go to SDSS Skyserver: http://skyserver.sdss.org/ and click on the Navigate tool.

Go to Navigate, and put in the cluster coordinates. Click "Search". Hopefully you'll see a cluster.

If you click on "Grid" (in Drawing Options), you'll get a scale bar at the bottom right which helps you work out the angular scale of the image. You can zoom in and out using the "+/-" buttons, and you can pan by click-dragging.

Note: Clicking "Invert Image" often helps you see things better. Also, clicking "Photometric Objects" or "Spectroscopic Objects" will highlight all objects which have photometric or spectroscopic data.

Click on a galaxy. The "quick look" panel will show a little zoomed-in image, the ugriz magnitudes, and (if it was observed spectroscopically), a thumbnail spectrum. Clicking on the spectrum will blow it up, or if you click the "Explore" button underneath the zoom window, a new webpage will open up with more detailed properties of the galaxy, and more tools.

Play around. Scroll, zoom, click on galaxies and hit "Explore", etc. Look at a few spectra of galaxies in the field. Work out the following:

Roughly how big (in arcminutes) is the cluster?
Compare the spectra of different galaxies: some ellipticals and some spirals. Do their spectra make sense given their morphology?
What is a rough guess for the redshift of the cluster?
See if you can find a background quasar. They will be very small (unresolved) objects, and blue, and will have a spectrum you can look at.

VERY IMPORTANT: When Navigate says an object has type = STAR, that does not mean it is actually a star. It only means that it is an unresolved point source. It might be a star, but it could also be a small, unresolved galaxy.