Thursday, June 18, 2009


Today I made my first weight maps. To do so I first normalized the pixel values of the flat field by dividing all the values by the maximum value. The I combined the flat field and bad pixel map by multiplying the values of each pixel in these two images. So the weighted maps look much like the flat fields, but don't have the bad pixels and cosmic rays.

Then I made MEFs of these weight maps for each exposure in each band.

Finally, I swarped the previously MEF'd .fits images with their respective weight maps. I combined them using the "WEIGHTED" method in swarp which stacks the images using a weights average. My weight map type was "WEIGHT_MAP".

The r stack looked pretty good, although it didn't get rid of all the streaks that we had attributed to bad pixels. The g stack pretty much just looked terrible. So I manually set the suspect pixels to zero in an effort to maybe pick up some bad pixels that had been lost.

Because the r stack was looking alright I went ahead and DAOphot'd it to check out how deep it was getting. The verdict: 19th magnitude! This is about a magnitude deeper than before so we should be down to 26th magnitude with calibration.

After emailing with Dave, we decided that the divide-by-the-max-value method of normalization wasn't a good one. In fact, because the average value of our flat was about 1, we're going to assume they're already normalized.


1. Finish re-making all the weight maps using this assumption
2. re-MEF them
3. re-swarp everything
4. Check out the stacks--if good/better then DAOphot
5. if DAOphot'd then do calibration and CMD
6. if good CMD then revel in it for a while.

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