PrismFo

Focusing with PRISM

1. Using the focus routine in LOIS

Make sure that you have sourced the "prismstart.tcl" script
Make sure that your object coordinates are correct
if your "User Button" window is not open, open it with the "Show User Buttons"
Use the !focustool button, this button calls a script that will create the files that the IDL focustool
procedure uses.
Based on the inside or outside temperature, use the appropriate formula
- F(T_in)=4164.89-7.96(T_in)
- F(T_out)=4172.22-8.19(T_out)
Set the parameters in the focustool button with the parameters set to the follow suggested values:
- xctr = Star's x position or column value
- yctr = Star's y position or row value
- expt = The exposure time that you want to use in seconds
- focstart = Value found in step e. minus 200
- focstep = 25 motor steps
- nfoc = 16 number of times to move 25 steps Note When the seeing is really bad(>3") you should consider 32 time around your best focus position.

Special Notice

If LOIS crashes during the script run. You must redo your storage path configuration in LOIS. See LoisStoreError for information

2. Run the IDL focustool widget to determine the best focus on Saturn

In your data directory, there is a focus sub-directory. Change your current working directory to that
directory with a "cd focus"
Run the command idl
Compile the focustool program in your IDL window

IDL> .r focustool

IDL> focustool

hit the button "Load Data"
Select the "focus.list.x" for the most recent focus run. If
it was your first run the file name will be "focus.list.1".
This file will be in the focus sub directory in your current data storage directory
When the program complete there will be a best focus value display in the data window above the graph.

Note

If you find that the focus value appears to be way off of the temperature solution(F>200) then you might try running FI on the move computer.

-- Main.BrianWTaylor - 01 Jan 2008