Wednesday, May 27, 2009

Update on where I am

I stacked the 7 exposures for the g-band and got them looking nice.

I then checked out the psfs of the sources on both the 10-exp and 7-exp stack of the g-band data to see if the sources looked okay. They looked decent--a little raggedy around the edges but otherwise circular. Neither looked particularly better than the other. I'll take a look at the CMDs of each to see if there are differences.

I took a look at the sky levels for the r-band data and discovered that exposures 138 and 139 are much different from the others. Even the ones with comparable values don't seem to follow any trend as far as I can tell. I will ask Beth about this tomorrow and in the meantime make a stack of the 8 exposures that seem consistent. The levels for the r-band are also much higher than those for the g-band, but I think this is okay as long as all 10 are in the same ballpark.

I also stacked the 10 exposures of the r-band and there's something funky happening with at least one exposure on Chip 3. The same shows up in the 8-exposure stack. Oddly enough, I'm seeing this in ds9, but it doesn't show up when I look at the stacks in atv. I'm not sure why this would be, but the images look fine in atv. I also looked at the psfs of both stacks using atv and they look fine.

I discovered that the problem I was having earlier with stacking the images was in fact a result of me averaging the exposures in the stack instead of medianing them. Because the averaged stacks looked so messed up, this is reason enough to use a median instead of an average, in my opinion.

Once I take a look into what's happening on Chip 3 in the r-band, I'll go about adding the sky back in. I'll do so by adding a constant background, the value of which will be the median of the median background level on each chip. Of course, this constant will be different for the g- and r-bands.

After the sky's back in, I should be set to daophot which I think I should be able to at least begin by the end of the day tomorrow.

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