Wednesday, July 7, 2010

Yesterday I screwd something up with the completeness calculation when I went to apply Dave's suggestion. For some reason the positions of the artificial stars weren't matching properly and so I was getting screwy completeness numbers. I ended up remaking the masterlist and that fixed the problem. I think I had inadvertently changed the addstar files and so they weren't matching properly with the masterlist.

In lieu of a better fix, I manually changed the addstar input magnitudes in the g-band by 0.35. This is the average value of the offset in the g-band brighter than r=24.5. Unfortunately when I was doing the post-allframe analysis I screwed up one of the allframe files so I have to re-run it. (In case you ever wondered why I keep the same files in so many different places, that'd be why; in one iteration of daomatch, you can corrupt an allframe file and have to re-run everything. C'est la vie. One allframe finishes again, the rest should be quick and the offset should be gone.

I was thinking about the nature of fixing the problem this way and it made me concerned about the way I was planning to calculate the photometric uncertainties. At first I thought that I would need to think of a different approach because in tweaking the offsets, I could easily just tweak them so much that the photometric uncertainties would turn out to be artificially low. However, the output magnitudes which I use to calculate the offsets must follow from the arbitrarily chosen magnitudes I input. And so the tweaking wouldn't be a problem as long as it's done pre-daophot/allstar/allframe. This is something I've been working on justifying to myself and I think I finally have.

While allframe runs, I've been working on Dave's approach to a chi and sharp cut. He suggested that we base our cuts on the envelopes defined by the artificial stars. These are very well behaved so it makes total sense. I empirically determined the envelopes and then interpolated functions to define the upper and lower limits on chi and sharp. My functions look good, but I'm trying to use a where statement to define the areas of chi and sharp space to allow. When I plot the results, my stars aren't within those bounds, so there's still a bug in the code. I think I need to take a break from it and come back later tonight. It'll be a good chance to take solace in the a/c in the lab instead of my sweltering apartment.

Tomorrow (not in this order):
1. With my new masterlist defined by the chi and sharp functions,
  • calculate the completeness and see how awesome it looks
  • run the ML code to see if the results are better behaved; if they're not, I'll need to make a choice about a brighter completeness limit to use for the ML calculation.
2. Edit the code for the artificial star tests so that I can run multiple tests. The positions of the stars need to be offset by a small amount each time. I also need to iteratively change the seed for the random selection of my stars to change things up a bit. Then start allframing like crazy!