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 small and simple applet is designed to be a precursor to using real data with the Fits Handler applet.

In this applet we simulate the detectablity of stars on a CCD.

The intensity of the stars and the number of stars that can be shown are controllable via parameter tags. The FWHM of the star is also controllable via parameter tags so one can show the effects of poor seeing, etc.

There are a minumum of basic controls. These are:

• Bias This slider controls the amount of bias + noise (mostly noise) in the background.

• Measure: After the bias is set to some level hit the measure button to make an "exposure". You will now see virtual stars on the detector. Contrast can be adjusted via the Min and Max slider bars.

• Mostly this applet is qualitative in terms of showing detectability of stars as a function of noise. However, you can be quantitative by drawing a box around the star. The mean, sigma and total counts are shown in the readout boxes.

Suggested Activities:

• The idea here is to set up different kinds of observing conditions for the students using the parameter tags (see below). The object is for the students to understand that detection of a star means detection against detector noise.