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So currently I am very close to attaining the first goal. The second goal is a bit tricky because of the mass of data I have to churn through, but hopefully I'll be able to get the code right soon.
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Stubbs' comments July 31 2013:
I'm unclear on whether you're still working with MDF images or have shifted over to NCP data. The advantage of the latter is that apart from clouds the magnitudes should be essentially the same from night to night, and so the effects of water content variation should be easy to pick out. Here's a re-iteration of what I sent via email on July 26:
1) make sure you can identify a common set of stars that have many data points
2) extract a table of magnitudes vs. time. The g and r bands should be insensitive to water, while i,z,y
3) find the instances of data being taken in photometric conditions (a common stable zeropoint)
4) see what the range in airmass is, since the field of view is a few degrees, and plot colors vs. airmass. Correct if necessary
5) then plot the set of airmass-corrected colors vs. time, and look for variations on the timescale of a few days that might be
due to water vapor.
6) for each star, determine the median colors (r-i), (r-z), (r-y), and (z-y). Plot the departures from the medians as a function of
the median color. Do redder stars have bigger excursions?
7) make some SLR plots and see if there is a measurable signal there.
I think the specific response to your question about what to plot is in items 5-7.
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Data access on Odyssey:
- Run JAuth.jar to get login key
- ssh -Y into to odyssey.fas.harvard.edu, or herophysics.fas.harvard.edu, using the electronic key.
- run tcsh
- source .myrcstubbs
- data are at /n/panlfs/data/MIRROR/ps1-md/gpc1/
- nightly science uses individually warped images, nightly stacks run on stacked frames
- image types: wrp is warped.
- see available modules with "module avail"
- load a module with "module load hpc/ds9-5.6"
- photometry is in .cmf files, as FITS tables.
- in python:
- import pyfits as p
- p.open('filename')
- print a[0].header
- or, imhead on command line
- a[1].data.AP_MAG for aperture magnitudes
- PSF_RA and PSF_DEC are in the skycell files.
- make a scratch directory for data in /n/panlfs
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