CG4 photometry: more detailed instructions

Follow the instructions on the Units page under "getting the number APT needs" (near the bottom of the page). These are the numbers I got for my SA101 mosaics. Are they right? Are they the same as what you'd use for the online mosaics?

	step 1	        step 1	         step2	        step 3	        step 4	    step 5 -- # for APT
chan	CDELT1	        CDELT2	        sq deg/px	sr/sq deg	sr/px	     convert to Jy/px
i1	0.000169	0.000169	2.8561E-08	0.000304847	8.70674E-12	8.70674E-06
i2	0.000169	0.000169	2.8561E-08	0.000304847	8.70674E-12	8.70674E-06
i3	0.000169	0.000169	2.8561E-08	0.000304847	8.70674E-12	8.70674E-06
i4	0.000169	0.000169	2.8561E-08	0.000304847	8.70674E-12	8.70674E-06
m1	0.0006944	0.0006944	4.82191E-07	0.000304847	1.46995E-10	0.000146995

Then:

1. stick this value in the conversion value under more settings
2. turn on background subtraction in more settings (option B)
3. apply settings. Close window
4. change to 6, 6-14 px for aperture, annulus
5. do photometry (click on object, calculate or recalculate values)
6. write down "source_intensity (sky-included)" because this is the sky minus the scaled background from the annulus
7. repeat for each object of interest
8. multiply measured fluxes by aperture correction (band-dependent -- see below)
9. compare these final flux densities to other people's flux densities

Aperture corrections. See photometry pages for explanation of what and why. The aperture corrections are a function of the aperture and annulus you used, compared to what the IRAC team uses to calibrate the instrument. Here are the aperture corrections for a NATIVE PIXEL 3, 3-7 combination; we have half the pixel size, so this corresponds to 6, 6-14 in arcseconds. Different pixel scales require different combinations.

real reference: http://ssc.spitzer.caltech.edu/irac/iracinstrumenthandbook/32/