Friday, June 12, 2009

Okay, here's the word.

I'm having issues with the single exposure CMD. Out of ~3000 stars in each catalog, I'm only getting ~30 that match to within .5 arcsec. I'm getting 156 to within 1 arcsec...but shouldn't it be that there aren't too many more matched when I bump this to 1 arcsec because everything's already been matched? The comforting news is that these are matching to those python found...but that's only slightly comforting.

Because...when I go to match to the SDSS catalog not a single star matches. I've thought about this for a while now and can't figure it out. Even if the 30 stars were the only ones that matched between the bands, my SDSS catalog is centered on Wil1 which is on chip 7 so I'm having a hard time believing it's not finding any matches.

I took a look at the single exposures in each band and compared the star-subtracted image from the not-subtracted image. There are some donuts associated with the bigger stuff but I would say th majority are subtracting really well. This is true for both bands. But taking a look at the stacks, there seems to be a much bigger problem with donuts in both bands. I'm wondering if the fitting radius shouldn't be increased for stacks?

I made a CMD of the stacks daophot'd with the old .opt parameters. There's a slight hint of getting deeper--one star fainter than 24 mag. But beside that they look about the same.

Like I mentioned before, I couldn't make a CMD of single exposures because I'm not finding any stars to calibrate.

1 comment:

  1. Hi Gail - If you're working on the weekend at all... can you copy the code you are using to match the single-exposure .als output? I'll see if I notice anything suspicious from the code side of things.