Monday, June 15, 2009


Beth spotted a bug in my calibration code so suddenly we're down to 25th magnitude. Now I'm comparing the calibrated CMD's made from the old .opt files and the new ones. I'm comparing between CMDs of the stack and CMDs of a single exposure on Chip 7. If only I could figure out how to attach plots to the blog, I could show them here, though I think maybe they're too big.

Anyhow, I'm noticing that the stacked images seem to get to the same depth using both new and old .opt files. The colors are slightly different between them, but no other noticeable difference. For the single exposures, a few stars show up in the old .opt CMD that are at fainter mags than in the new .opt CMD. I'm thinking the newer one probably cuts these out at some point because it's more robust and the general cutoff seems to be at ~23.5 or 23.75 for both anyway. I already know the new .opt files turn up fewer stars and the stacks get to the same depth, so I think everything is legit here.

However we're still working on getting deeper because we expected calibrated CMDs down to 26 or 26.5. While more brainstorming on this continues, I'm going to work on getting my calibration code up to snuff. And then I'm going to the sound wave panel at 4 this afternoon.


I checked out the offsets as a function of position in both bands and for both the new and old .opt files. They all seem to be independent of position, which is a good thing. There does appear to be one star or so in both bands and both the new and old .opts that is a lot higher than the rest, but I don't think this is a big deal. If anything, I can cut it out later.

I then moved on to do the linear fit to the zero-pt versus color data. I'm a little confused, though--should I have two fits, one for each band? Since both have a different zero-pt, this must be the case. I guess I'm just a little confused as to what the fit is going to be used for. I understand that when I calculated the zero-point offset I had to add that back into the instrumental magnitude. But color involves both magnitudes and they have different color terms. Will I be adding the color term for each band back into the magnitude in that band to adjust the calibrate the color?


More calibrating.

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