Calibration Process

The calibration process is very easy, since most of it is automated. Its "home base" is in pawnee:/data/calibration. You need to do calibrations for all standards taken on any given night. Each night's calibrations will be performed separately.

Summary of Steps for Quick Reference
      1. Fill out standards.txt for one night, using PHOT to determine counts.
      2. Run to create files.
      3. Repeat for all nights.
      4. Add lines to files, by filter and chronologically, include any comments, and tweak spacing.

Detailed Steps
1. Open up standards.txt. Fill this table out with all standards for one night, following the column headers, a separate line for each standard. Notice that all the necessary information can be found in the observing log, with the exception of counts (see #2). A couple of notes on formatting: The object name must, if possible, be reduced to four characters long (as in fe34 or bd33). If the name is fewer than four characters by default (as in hz4), you can leave it as three characters. Also, remember to include a decimal point in every counts value, even if phot returns a whole number. This will allow the value to be regarded by IDL as a floating point value instead of an integer. An example line with proper formatting:
      Night                  Fits      Filter      ObjName      ExpTime      Temp(F)      AM      Counts
      oct10112007      a013    8685       bd28             30                 53                1.03     144843.2
2. Now we need to determine the counts for each standard. To begin, display a standard in ds9 and verify which star is the standard using the finder charts or on Carolyn's landolt page(you may need to xy-flip the image in ds9). Now, run PHOT on this star to determine optimal values for aperture, annulus, and dannulus to measure its counts. See my photometry page for help on using PHOT. Enter these counts into standards.txt, as shown in #1.
3. This process requires a lot of math to calculate many different quantities. Fortunately, I've automated this with an IDL program called This program will calculate everything and create a file with a table of all necessary information. As a reminder, to run IDL programs: open IDL, compile the code by typing ".r," and run the program by typing "calibration." If all was done correctly, a new file should be created. For posterity, details about the mathematics required for calibration can be found on ShiAnne's calibration page.

4. Repeat the above steps for all nights. Remember to erase the new lines in standards.txt after each night's calibration is complete. No need to do a night twice.
5. We have also created master calibration files for each filter, called These master tables are in chronological order. Add the lines from the newly-created files into these master files. Make sure you append to the correct filter's master file, and continue the tables chronologically.
6. Finally, add to the last column of the master files any comments about the standards. Note if it was windy, if the flux is low (and thus nonphotometric), if there was high humidity, if the image was taken at a high airmass...anything that may lower the reliability of the calibration.