FOCUSING INSTRUCTIONS

The RCT currently focusses the telescope automatically using the focus script. This script reads one of the telescope temperature sensors and adjusts the focus position to what it thinks is corrrect. The program in theory takes account of the filter, but this part has been deleted.

Taking Focus data

Currently there is no automatic way to find the best focus. However, there is a rather arcane manual method that involves two steps: taking the data, analyzing the data.

focusdip is a script that will generate sixteen images with differing focal position. Do the following in an X-Window for best results 

cd to a scratch directory
Point the telescope up and looking out the slit (almost anywhere works) 
Have the tracking on
Select the filter you want to use
type: focusdip
If you have an X-window running, it will pop up a tv windows Showing the images, double check that there are usuable stars in the field. Type: killall tv to removed the tv images.

Determining the Best Focus

You will now have in your working directory sixteen files focus??.fits. You will then run the focusanl script Again in X-Windows: 
type: focanl
The script will pop up a tv window and ask you to use the cursor to pick a nice star
move the cursor and click once with the left button.
If all goes well it will pop up a montage window  
And a focus graph  
Type: spawn to exit the program.
If all went well, it will ask you you want to enter the data into the database
Answer y if you trust it, n if you don't.

Determining the Focus Algorithm

Each time you measure focus it enters into the Focus table. What do with this data is to be determined.

Instructions Index