Photometric Catalogue Recipe

1. Measure the pixel scale on each image (using image->WCS conversion in ds9), because the mosaic you have may differ from what is on original frame.

2. Then find the frame that you are interested in to have detection, it might be the frame that is the deepest or biggest file or the filter in which objects of interested are appearing

3. Change the WHT created by multidrizzle into RMS using IRAF command:

imcalc weightmap.fits rmsmap.fits "1/sqrt(im1)" pixtype=double

!!FIRST THIS THAN SWARP!!! It makes the difference the order it seems that first imacalc and then swarp is the correct one

4. Make the detection (extractor) in this chosen filter (eg 814) and measure auto mag and aperture mag using at least two different apertures

remember that:

for average stack: gain=GAIN*N

and for median: gain=2/3*N*GAIN

5. If the two frames differing with size and resolution use swarp on all frames separately to change scaling and size (remember about any weight maps!):

for egxample:

COMBINE Y

COMBINE_TYPE MEDIAN

#-------------------------------- Astrometry ----------------------------------

PROJECTION_TYPE TAN # Any WCS projection code or NONE

PROJECTION_ERR 0.000001 # Maximum projection error (in output

CENTER_TYPE MANUAL # MANUAL, ALL or MOST

CENTER 13:47:31.667, -11:45:14.46 # Coordinates of the image center

PIXELSCALE_TYPE MANUAL # MANUAL,FIT,MIN,MAX or MEDIAN

PIXEL_SCALE 0.147828 # Pixel scale

IMAGE_SIZE 1500. # Image size (0 = AUTOMATIC)

6. The two frames after resampling are differing the FWHM, smooth the one with lower FWHM using gauss command in IRAF. Remember to smooth RMS_MAP as well

WFC3:

814:0.7

ISAAC:

814: 1.2

FORS:

814: 2.55

V: 0.8

B: 0.5

7. For the rest of the frames sextractor has to be used in double mode system reporting only aperture mag also with 2 different apertures (2 and 3 FWHM)

!!!!Always do detection on non smooth image and remember to do measurement on smooth detection image as well!!!!

sex 814sci.fits,814sci_gauss.fits -c 814_2FWHM.sex

sex 814sci.fits,814sci_gauss.fits -c 814_3FWHM.sex

sex 814sci.fits,H_sci.fits -c H_2FWHM.sex

We want similar detection in all cameras, hence,

For EACH camera change the

DETECT_THRESH 0.30 I don't know why it has to change, but it has to!

DETECT_MINAREA 3 ; there are significantly less pixels that it covers so recalculate it according the pix scale

BACK_SIZE 51.8 ;this same as above, it does change number and kind of detection!!!

DEBLEND_MINCONT 0.05 ;even if the frame is not smoothed the objects are now less seperated

so that there will be similar kind and amount of detected objects.

Neither GAIN nor Pixel Scale in extractor changes the detection amount

8. Report the mag of objects (eg in R-band) using the formula:

R_mag= Detection_filter_mag_auto+R_mag_aper-Detection_filter_mag_aper_smooth_and_rescaled_to_R_band