ELBRUS CALIBRATING TUTORIAL

How to have selected stars in my images


We are here because no star was selected after pressing the 'Analyze' button (or not enougth stars were selected).
If after pressing the Analyze button you have stars rounded by a red circle you can skip this page.

We give the three most usual situations that lead to a no selected star situation.
** A wrong threshold value is very usual. So let the program search automatically the good value.
** At the beginning, you don't know what your pixel-size parameter is. If the pixel size parameter is too big, you'll have all the stars selected in a cluster like in Situation 2 bellow.
** On the contrary, if your pixel size parameter is too small, probably only one or two stars will be selected. This is because the program don't select stars neareast than 0.4 arc minutes. (Your pixel size is too small --> your image size is too small --> all the extracted stars are too near one to the other. )
Situation 1:

What happens here is that we have a bad threshold value.
Solution: Check the 'Auto' check box.


Situation 2:

Here we have a too large pixel size.
Solution: Drag the mouse over the image with the left button down, and draw a little box. Then rightclick and select 'Analyze outside the rectangle'


Situation 3:

Here the pixel size is too small. The distance between selected stars must be > 0.4 arc minutes
Solution: go to the 'Others' 'Edit parameters' menu and just type a greather pixel size. For example try 1.0


You can now proceed with the next step: Determining my parameters

Or move back to Are my images reversed ? Example 2

(Updated November 15, 2008 Alfonso Pulido)