[ ESO ] La Silla


Zero Point Monitoring 


This page describes how to monitor the WFI Zero Points using a quicklook tmag program on the w2p2off machine. The program creates a database of measurements allowing us to monitor the photometric quality of the night, as well as establishing a database of measurements which can be used at a later date to obtain full photometric solutions.

When to Use it

You should run this every service night that you deem photometric. That way, you can see whether the night is indeed photometric and stays that way. Also, the results are written to a logfile so that we can go back later and do a full photometric solution. This is the best way to accumulate data for photometric studies of WFI without having to save all the data somewhere!

How to Use it

On w2p2off:

For every image of a standard, in midas: This will extract some files and ultimately display the chips, one at a time, in the display window of midas. If the program thinks there should be a standard star in the frame, it will overplot a red cross on the image, one for each star it thinks should be there. These crosses should be relatively close to the actual stars.

For each chip, you need to left mouse click on one of the red crosses, then left mouse click on the star the cross corresponds to. The program will then match up all the crosses with their respective stars on that chip (well as good as it can - don't worry if it misses a few).

The next chip will then be displayed with relevant crosses and you must repeat the procedure of clicking on one of the crosses and then it's corresponding star.

If there is no cross in the field, or if there is only one cross in the field (so the identification is ambiguous), double click the right mouse button to skip that chip.

The program will then plot up the zeropoint just measured, as well as zeropoints from previous nights. From here you can see whether the image you have just taken is consistent with a photometric night.

Move on to process the next image.

If You Have Questions

Olivier Hainaut wrote the program and so is the master of all. Lisa Germany is his devoted diciple and vaguely knows what she is doing.

Send comments to : ls-wfi
Last modified: Sat May 17 2008 
[Observing][ESO La Silla][The SciOps Home Page][ESO][Index][Search][Help][News]