| | 1 | I selected 5 ISP images (same field, different bands) to calculate the zeropoint. |
| | 2 | |
| | 3 | These were the 5 images, all 5 second exposures (typical for ISP): |
| | 4 | |
| | 5 | ||isp/20100225/o5252i0361o03/o5252i0361o03.chip01.fits|| |
| | 6 | ||isp/20100225/o5252i0361o04/o5252i0361o04.chip01.fits|| |
| | 7 | ||isp/20100225/o5252i0361o05/o5252i0361o05.chip01.fits|| |
| | 8 | ||isp/20100225/o5252i0361o06/o5252i0361o06.chip01.fits|| |
| | 9 | ||isp/20100225/o5252i0361o07/o5252i0361o07.chip01.fits|| |
| | 10 | |
| | 11 | I then used dvo, and the bright star catalog (catdir.synth.bright), to find some bright stars that I could match (by eye) to the images. I found 10 stars (the same 10) in g, i, and r band, only 9 (in z), and only 3 in y (I found 5 more to get a better estimate). |
| | 12 | |
| | 13 | psPhot was used to get instrument mags for these stars, and the zero point was found by taking the median of (catmag - instmag - 2.5log10(exp_time)) |
| | 14 | |
| | 15 | These are the ISP zeropoints I calculated: |
| | 16 | |
| | 17 | ||band || ZP || stddev || |
| | 18 | ||g ||19.3 || 0.3|| |
| | 19 | || r || 19.1 || 0.3 || |
| | 20 | || i|| 18.4 || 0.2|| |
| | 21 | ||z|| 17.2 || 0.1 || |
| | 22 | || y || 14.0 || 0.8|| |
| | 23 | |
| | 24 | Here are plots of ZP vs instrument magnitude, for the various bands: |
| | 25 | [[Image(isp.zpoints-0.jpg)]] |
| | 26 | [[Image(isp.zpoints-1.jpg)]] |
| | 27 | [[Image(isp.zpoints-2.jpg)]] |
| | 28 | [[Image(isp.zpoints-3.jpg)]] |
| | 29 | [[Image(isp.zpoints-4.jpg)]] |
| | 30 | |
| | 31 | |
