Two windows should be open. This one in which the instructions are given and a smaller one which contains the actual applet that we will be using.Tutorial: This applet allows the student to measure the parallax of stars that are contained in the Third Catalog of Nearby Stars. There are a myriad of exercises that one can do here and that can be set up by the Instructor via parameter tags (see below). The basic intent here is to have the students measure a parallax by using a virtual earth sun baseline. Errors are hard coded into each measurement and an error histogram is given. There are options to take either a small number of measurments or a large number. If you want to use this applet to demonstrate error propogation then have the students make only 3 measurements per star and produce an HR diagram from that. Then have them repeat the exercise by having them make 100 measurements (50 years worth of data) to see how things have improved.
The overall features of this applet were described on the intro page.
Because this applet has a wide range of possible usage (i.e. a term
project could involve student teams using all 3000 stars but working
in different parts of the sky) we will just list the parameter tags
here to show how different cuts in the catalog can be made to show
different kinds of stars.
|
| Parameter Tag | Functionality |
|---|---|
| min_mag | Sets the magnitude below which stars in the catalog aren't displayed. Very useful if you just want to see the trig parallax sample for the brightest stars in the catalog. so 1000 angstroms would be 10E-7 meters. |
| min_par | Minimum parallax to use. would select only stars whose parallax is larger than 0.2 arcseconds. |
| max_par | Minimum parallax to use. |
| min_vel | Velocity information is also available so you can select on velocity if you want (high velocity metal poor subdwarfs?) |
| max_vel | Maximum velocity to use. |
| bvmin;bvmax | You can do color cuts if you want selected via bvmin and bvmax. So if you want to display only red stars then ; would do just that. |
| port | This is currently set to 7777 on the server. By setting this you allow the students to store files temporarily on the server. Students give it a unique file name and their data (e.g. B-V and Luminosity for the selected stars) is sent to the server. This file can later be read and added to by the student. |